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Invited Review: Applying fungicide on corn plants to improve the composition of whole-plant silage in diets for dairy cattle*

      ABSTRACT

      Purpose

      Published literature and data from the author’s group pertaining to fungicide application on corn plant used for whole-plant corn silage (WPCS) was reviewed to summarize the effects of the aforementioned strategy for fungi disease control in the corn plant on WPCS quality and dairy cattle performance.

      Sources

      The main source of data and information for this review was peer-reviewed literature.

      Synthesis

      Whole-plant corn silage is the most commonly used forage in diets of dairy cattle in the United States. The interaction of fungi and corn plants reduces yields, decreasing the efficiency of food production, and the nutritive quality and value of this material when fed to ruminants. When infecting the corn plant, fungi reduce its nutritional content available by metabolizing sugar compounds within the plant cell. Applying fungicide to corn plants can protect corn plants from fungal infection, therefore limiting yield losses and increasing the nutritive quality of the plant material. There is limited information regarding feeding dairy cows WPCS from corn plants treated with foliar fungicide. However, findings from previous research highlight the negatives of making and feeding WPCS from diseased corn plants.

      Conclusions and Applications

      Scouting corn plants for foliar disease is an important practice to determine fungicide application. Nevertheless, foliar fungicide application on corn plants used to make WPCS for dairy cattle seems to improve its nutritional composition. Mainly, factors attributed to it are increased milk components and feed efficiency, reduced fiber concentrations, and improved ruminal degradability, independently of visual identification of foliar diseases.

      Key words

      INTRODUCTION

      On a DM basis, whole-plant corn silage (WPCS) composition is about 60% corn ears, 12% corn leaves, and 28% corn stalks (
      • Kuehn C.
      • Linn J.
      • Johnson D.
      • Jung H.
      • Endres M.
      Effect of feeding silages from corn hybrids selected for leafiness or grain to lactating dairy cattle..
      ). For dairy cattle diets, WPCS represents 40 to 60% of the total mix ration in lactating diets (
      • Mueller D.
      • Wise K.
      Corn Disease Loss Estimates from the United States and Ontario, Canada—2013.
      ). One of the many parasites that can affect corn plants are fungi. The triangle of the disease is composed of the host (corn plant), pathogen (fungi), and environment (i.e., weather, soil). Corn plant physical barriers such as cell walls and chemical releases (i.e., secondary metabolites) aid plants in protecting from pathogens (
      • Malinovsky F.G.
      • Fangel J.U.
      • Willats W.G.
      The role of the cell wall in plant immunity..
      ). Fungi maintains tissue growth by obtaining nutrients from the plant. That is accomplished consistently if fungi remain undetected on the plant surface, where enzymes degrade cell walls and once inside produce toxins killing the plant tissue (
      • Sexton A.C.
      • Howlett B.J.
      Parallels in fungal pathogenesis on plant and animal hosts..
      ).
      Plants have adapted by increasing the lignin concentration in the secondary cell wall, thus creating a thicker layer for digesting when distressed or infected with a fungal pathogen or insect (
      • Santiago R.
      • Barros-Rios J.
      • Malvar R.A.
      Impact of cell wall composition on maize resistance to pests and diseases..
      ). However, once inside the cell, and growth has ceased, fungi release secondary metabolites, which in some species are toxic. It is generally hypothesized that during the colonization and sporulation phase of a fungus within a plant, mycotoxins are secreted by growing colonies (
      • Calvo A.M.
      • Wilson R.A.
      • Bok J.W.
      • Keller N.P.
      Relationship between secondary metabolism and fungal development..
      ). Therefore, one can hypothesize that foliar fungicide application may improve WPCS quality.
      Corn plants treated with fungicide had fewer yellow leaves than nontreated corn plants (
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      ), and WPCS from corn plants treated with fungicide had improved fermentation profile during the ensiling period compared with WPCS from corn plants that were not treated with fungicide (
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application effects on plant composition of a silage variety corn..
      ).
      • Haerr K.J.
      • Lopes N.M.
      • Pereira M.N.
      • Fellows G.M.
      • Cardoso F.C.
      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
      reported that cows fed WPCS from corn plants treated with foliar fungicide tended to have improved feed efficiency. Therefore, the objectives of this review were to summarize the knowledge available on the fungi and plant relationship, limiting plant infection by applying fungicide, and how WPCS from corn plants with fungicide application affects dairy cow performance.

      REVIEW AND DISCUSSION

      Fungus and Corn Plant

      Field Challenges

      Corn products are undeniably an important source of feed for cattle in the United States. Whole-plant corn silage is one of the most essential corn products used for dairy operations; approximately 89% of dairy farms incorporated WPCS in diets for lactating cows in 2014 (
      • USDA
      Dairy 2014.
      ). Globally, the United States produced the most corn in 2014 at 327 million tonnes with approximately 14% of total corn production devoted to the production of WPCS (
      • USDA
      Dairy 2014.
      ).
      During growth, the corn plant undergoes 2 phases of development: vegetative stages and reproductive stages (Table 1;
      • Mueller D.
      • Pope R.
      Corn Field Guide.
      ). The main physical changes occurring in the corn plant at the vegetative stage are the emergence of the tassel and the development of full plant height (
      • Nleya T.
      • Chungu C.
      • Kleinjan J.
      Chapter 5: Corn growth and development.
      ). At the R5 corn stage of growth, the milk line (a distinct horizontal line) forms between the yellow and white areas on the kernel, almost all of the kernels begin to dent, and the moisture of the corn kernels reaches approximately 55% DM (
      • Nleya T.
      • Chungu C.
      • Kleinjan J.
      Chapter 5: Corn growth and development.
      ). This is the stage at which most WPCS reaches between 30 and 38% DM, being mature for harvest (
      • Mahanna B.
      • Seglar B.
      • Owens F.
      • Dennis S.
      • Newell R.
      Silage Zone Manual.
      ).
      Table 1Corn plant growth stages
      StageAbbreviationDescription
      Vegetative
      The vegetative stages are determined based on the total number of leaves with a visible collar (off-white band at the base of the leaf blade where it extends away from the stalk; Mueller and Pope, 2009).
      VEEmergence of the shoot from the soil
      Vegetative
      The vegetative stages are determined based on the total number of leaves with a visible collar (off-white band at the base of the leaf blade where it extends away from the stalk; Mueller and Pope, 2009).
      V1Development of a collar on the lowest leaf
      Vegetative
      The vegetative stages are determined based on the total number of leaves with a visible collar (off-white band at the base of the leaf blade where it extends away from the stalk; Mueller and Pope, 2009).
      V2Development of a collar on the 2 lowest leaves
      Vegetative
      The vegetative stages are determined based on the total number of leaves with a visible collar (off-white band at the base of the leaf blade where it extends away from the stalk; Mueller and Pope, 2009).
      V(n)Development of up to 17 to 22 leaf collars
      Vegetative
      The vegetative stages are determined based on the total number of leaves with a visible collar (off-white band at the base of the leaf blade where it extends away from the stalk; Mueller and Pope, 2009).
      VTAppearance of the lowest branch of the tassel (tasseling)
      Reproductive
      The reproductive stages are determined based on kernel maturity (Mueller and Pope, 2009).
      R1Any silk visible on the cob
      Reproductive
      The reproductive stages are determined based on kernel maturity (Mueller and Pope, 2009).
      R2Kernels are small and white and the endosperm fluid is clear
      Reproductive
      The reproductive stages are determined based on kernel maturity (Mueller and Pope, 2009).
      R3Kernels are yellow with milky white fluid
      Reproductive
      The reproductive stages are determined based on kernel maturity (Mueller and Pope, 2009).
      R4Kernel contents are pasty as starch accumulates
      Reproductive
      The reproductive stages are determined based on kernel maturity (Mueller and Pope, 2009).
      R5Most kernels are dented due to starch hardening at the top of the kernel
      Reproductive
      The reproductive stages are determined based on kernel maturity (Mueller and Pope, 2009).
      R6Milk line is no longer visible and a black layer forms at the kernel’s attachment (end of DM accumulation)
      1 The vegetative stages are determined based on the total number of leaves with a visible collar (off-white band at the base of the leaf blade where it extends away from the stalk;
      • Mueller D.
      • Pope R.
      Corn Field Guide.
      ).
      2 The reproductive stages are determined based on kernel maturity (
      • Mueller D.
      • Pope R.
      Corn Field Guide.
      ).
      Due to the importance of WPCS in the diet of lactating dairy cows, WPCS quality control is pivotal for dairy producers’ and nutritionists’ success. In fact, recent reviews describe in detail the current literature on WPCS feeding management and cow behavior (
      • Grant R.
      • Ferraretto L.
      Silage review: Silage feeding management: Silage characteristics and dairy cow feeding behavior..
      ), current recommendations on optimizing WPCS quality at harvest (
      • Ferraretto L.
      • Shaver R.
      • Luck B.
      Silage review: Recent advances and future technologies for whole-plant and fractionated corn silage harvesting..
      ), and common issues regarding DM and quality loss in WPCS (
      • Borreani G.
      • Tabacco E.
      • Schmidt R.
      • Holmes B.
      • Muck R.
      Silage review: Factors affecting dry matter and quality losses in silages..
      ). The effects of physical and chemical composition of WPCS during growth, harvest, and ensiling on cow health and productivity are well established. In addition to those results and recommendations, a variety of laboratory tests can easily be performed on WPCS and other feedstuffs to determine nutrient quality and a TMR so the feeding routine can be adjusted accordingly. However, the effects of fungal disease on WPCS both in the field and during storage after harvest are much more difficult to control.

      Yield Losses due to Fungal Infections

      In 2013, 7.5% of the total estimated corn harvested from 21 corn-producing states was lost to disease, meaning almost 27 million tonnes of corn was lost because of seedling blights and foliar diseases (
      • Mueller D.
      • Wise K.
      Corn Disease Loss Estimates from the United States and Ontario, Canada—2013.
      ). Under ideal weather conditions for pathogenesis, a 1% increase in foliar disease severity of gray leaf spot (GLS), caused by the fungus Cercospora zeae-maydis, reduced corn yields by 47.6 kg/ha when compared with a tolerant hybrid (
      • Nutter Jr., F.W.
      • Jenco J.H.
      Development of critical-point yield loss models to estimate yield losses in corn caused by Cercospora zeae-maydis..
      ;
      • Ward J.M.
      • Stromberg E.L.
      • Nowell D.C.
      • Nutter Jr., F.W.
      Gray leaf spot: A disease of global importance in maize production..
      ). Furthermore, in a meta-analysis of 20 studies, every 10% increase in rust severity on sweet corn, caused by the fungus Puccinia sorghi, reduced corn yields by 2.4 to 7.0% (
      • Shah D.A.
      • Dillard H.R.
      Yield loss in sweet corn caused by Puccinia sorghi: A meta-analysis..
      ). Mycotoxins, a secondary metabolite of fungi, contaminated 12.5% of the total harvested grain in the United States in 2013, mostly because of the disease Aspergillus ear rot (
      • Mueller D.
      • Wise K.
      Corn Disease Loss Estimates from the United States and Ontario, Canada—2013.
      ), caused by the fungi Aspergillus flavus and Aspergillus parasiticus (
      • Miller J.D.
      Fungi and mycotoxins in grain: Implications for stored product research..
      ). It is evident that fungal infection and disease in plants can cause devastating losses in corn yield.

      Fungal Interactions with Plants

      There are fungi that are not parasitic to the corn plant. Most fungi associated with plants are saprotrophs, responsible for decomposing OM as their substrate for existence (
      • Carris L.M.
      • Little C.R.
      • Stiles C.M.
      Introduction to fungi.
      ). Other fungi, about 160 known species, reside on the roots of growing plants in a mutualistic relationship (i.e., phylum Glomeromycota—the arbuscular mycorrhizal fungi). Carbohydrates produced by the plant feed the fungus, and the fungus transports nitrogen, phosphorous, and other minerals to the plant (
      • Carris L.M.
      • Little C.R.
      • Stiles C.M.
      Introduction to fungi.
      ).
      • Meng L.
      • Zhang A.
      • Wang F.
      • Han X.
      • Wang D.
      • Li S.
      Arbuscular mycorrhizal fungi and rhizobium facilitate nitrogen uptake and transfer in soybean/maize intercropping system..
      reported that inoculating with both arbuscular mycorrhizal fungi and rhizobium in the soybean–maize intercropping system improved the N fixation efficiency of soybean and promoted N transfer from soybean to maize, resulting in the improvement of yield advantages of legume–nonlegume intercropping. A very small amount of fungi are disease causing, totaling less than 10% of about 100,000 known species, that colonize plants (
      • Knogge W.
      Fungal infection of plants..
      ).

      Disease in Corn Plants and Pathogens

      Plant pathologists use the disease triangle for assistance when evaluating the likelihood of a disease outbreak. A susceptible host (plant), a pathogen, and a favorable environment are all necessary for development of plant infection, but the presence of just 2 is unlikely to result in disease. The relationship between fungi and plants is sometimes referred to as an arms race (
      • Malinovsky F.G.
      • Fangel J.U.
      • Willats W.G.
      The role of the cell wall in plant immunity..
      ). By definition, to be a pathogen, an organism must be able to cause disease and complete its life cycle on a host (
      • Sexton A.C.
      • Howlett B.J.
      Parallels in fungal pathogenesis on plant and animal hosts..
      ). Historically, fungi can be divided into 2 main groups, both of which originate in the field. Fungi produce toxins in the plant before harvest and a plant–fungus interaction is stablished. Fungus can be a problem after harvest and a function of crop nutrients, physical, and biotic factors (
      • Miller J.D.
      Fungi and mycotoxins in grain: Implications for stored product research..
      ).
      Once in the cell and after growth, the fungal pathogen either adapts to the host’s physiology or modifies the environment for nutrient uptake to allow for colonization within the host (
      • Knogge W.
      Fungal infection of plants..
      ;
      • Sexton A.C.
      • Howlett B.J.
      Parallels in fungal pathogenesis on plant and animal hosts..
      ). Once fungal pathogens invade, plant cell oxidative bursts signal other metabolic pathways of an invasion (
      • Boller T.
      • Felix G.
      A renaissance of elicitors: perception of microbe-associated molecular patterns and danger signals by pattern-recognition receptors..
      ) but in doing so locally kill plant tissue providing immediate nutrients to the fungus (
      • Sexton A.C.
      • Howlett B.J.
      Parallels in fungal pathogenesis on plant and animal hosts..
      ). For more long-term nutrition, a haustorium, a specialized fungal structure, can be inserted into the plant cell for water and nutrient uptake, especially hexose carbohydrates including sucrose, glucose, and fructose (
      • Voegele R.T.
      • Struck C.
      • Hahn M.
      • Mendgen K.
      The role of haustoria in sugar supply during infection of broad bean by the rust fungus Uromyces fabae..
      ). The diversion of plant nutrients can be used for fungal growth and development.
      Once inside the cell and growth has ceased, fungal pathogens release secondary metabolites, which in some species are toxic. It is generally hypothesized that during the colonization and sporulation phase of a fungus within a plant, mycotoxins are secreted by growing colonies (
      • Calvo A.M.
      • Wilson R.A.
      • Bok J.W.
      • Keller N.P.
      Relationship between secondary metabolism and fungal development..
      ). The exact function of fungal toxins in the plant is unclear. Fungal phytotoxins can cause direct plant cell death (
      • Sexton A.C.
      • Howlett B.J.
      Parallels in fungal pathogenesis on plant and animal hosts..
      ) by overactivation of the plant plasma membrane enzyme, H+ATPase, which disrupts energy transfer during the light reactions in the chloroplasts (
      • Knogge W.
      Fungal infection of plants..
      ), the closing or opening of the stomata, and the redirection of ion channels (
      • Elmore J.M.
      • Coaker G.
      The role of the plasma membrane H+-ATPase in plant-microbe interactions..
      ). However, mycotoxins threaten food safety and security worldwide.
      Five agriculturally important mycotoxins resulting from corn ear rot include deoxynivalenol (DON) from the fungus Fusarium graminearum; zearalenone (ZEA) from the fungus F. graminearum; ochratoxin A from the fungi Piper verrucosum and Aspergillus ochraceus; fumonisin from the fungus Fusarium moniliforme; and aflatoxin from the fungi A. flavus and A. parasiticus (
      • Miller J.D.
      Fungi and mycotoxins in grain: Implications for stored product research..
      ). Development of mycotoxins within the plant occurs later in the growth and development of the corn plant. One study reported that fumonisin concentration within corn kernels increased greatly as the corn plant became more mature, with only 33% of corn kernels infected at the fourth reproductive stage but 62.5% of corn kernels infected at harvest (
      • Ariño A.
      • Herrera M.
      • Juan T.
      • Estopañan G.
      • Carramiñana J.
      • Rota C.
      • Herrera A.
      Influence of agricultural practices on the contamination of maize by fumonisin mycotoxins..
      ). Furthermore, although it is generally thought tilling fields may reduce fungi colonization, this may not be the case as
      • Ariño A.
      • Herrera M.
      • Juan T.
      • Estopañan G.
      • Carramiñana J.
      • Rota C.
      • Herrera A.
      Influence of agricultural practices on the contamination of maize by fumonisin mycotoxins..
      reported no difference in fumonisin concentrations in varying degrees of tilled fields. The most prevalent mycotoxin present in WPCS in the United States in 2017 was DON (Table 2).
      Table 2Total number of positive samples, percentage of all samples that were positive, and percentage of total positive samples affected by each mycotoxin for whole-plant corn silage samples as analyzed by Agri-King Inc. (Fulton, IL), Rock River Laboratory Inc. (Watertown, WI), and Dairyland Laboratories Inc. (Arcadia, WI) in 2017
      MycotoxinTotal positive

      samples per

      mycotoxin
      Total number of samples that were positive for each mycotoxin upon analysis. Table created for Weatherly (2018).
      Positive

      samples,
      Percentage of all samples analyzed that were positive for each toxin out of all corn silage samples analyzed (n = 55,641).
      %
      Total positive

      samples affected

      by each toxin,
      Each mycotoxin’s specific contribution to the total number of positive samples (n = 5,249).
      %
      Aflatoxin1,3322.3925.38
      Zearalenone9881.7818.82
      Deoxynivalenol2,7014.8551.46
      Fumonisin530.101.01
      T-2 Toxin1750.313.33
      1 Total number of samples that were positive for each mycotoxin upon analysis. Table created for
      • Weatherly M.
      Food safety through fungal disease and mycotoxin mitigation on dairy farms: From field to feed and the rumen.
      .
      2 Percentage of all samples analyzed that were positive for each toxin out of all corn silage samples analyzed (n = 55,641).
      3 Each mycotoxin’s specific contribution to the total number of positive samples (n = 5,249).

      Corn Plant Defense Mechanisms

      The plant cell wall is composed of a primary cell wall, providing structural support for the plant, and a secondary cell wall, developing inside the primary cell wall only after the plant cells stop growing (
      • Freeman B.C.
      • Beattie G.A.
      An overview of plant defenses against pathogens and herbivores.
      ). The primary wall of plant cells is composed of cellulose, cross-linking glycans, also known as hemicellulose, and pectins. Cellulose is a polysaccharide, composed of β (1,4)-glyosidic bonds between glucose molecules, and very resistant to degradation by hydrolysis (
      • Ferrari S.
      • Savatin D.V.
      • Sicilia F.
      • Gramegna G.
      • Cervone F.
      • Lorenzo G.D.
      Oligogalacturonides: Plant damage-associated molecular patterns and regulators of growth and development..
      ). Hemicellulose is also a polysaccharide, where a pentose is bonded with a hexose (e.g., arabinoxylans, xyloglucans, mixed linked β glucans, and galactomannans). The cross-linking of hemicellulose aids in the fortification of cellulose for both structural support and prevention of microbial invasion (
      • Endler A.
      • Persson S.
      Cellulose synthases and synthesis in Arabidopsis..
      ). Enzymes such as xylanase, produced by some fungi, weaken the cell wall and allow fungal entry into the plant cell (
      • Belien T.
      • Van Campenhout S.
      • Robben J.
      • Volckaert G.
      Microbial endoxylanases: Effective weapons to breach the plant cell-wall barrier or, rather, triggers of plant defense systems?.
      ). Lignin, a phenolic polymer, is deposited during the last stages of secondary cell wall formation. Lignin reinforces plant cells and allows transport of water under negative cellular pressure (
      ). When cell walls become lignified, they become highly impermeable to pathogens and hard for insects to digest, limiting access to cell wall sugars (
      • Freeman B.C.
      • Beattie G.A.
      An overview of plant defenses against pathogens and herbivores.
      ).
      Plants have a recognition system controlled by resistance genes within the plant cell known as plant triggered immunity (
      • Jones J.D.
      • Dangl J.L.
      The plant immune system..
      ). Pathogen associated molecular patterns, also known as PAMP, which may include fungal chitin or bacteria flagellin, can trigger a plant triggered immunity response within the plant cell to prevent microbial colonization (
      • Medzhitov R.
      • Janeway Jr., C.A.
      Innate immunity: Impact on the adaptive immune response..
      ). Also, damage associated molecular patterns, known as DAMP, which may include parts of the plant cell wall released possibly due to fungal enzymes, trigger an immune reaction (
      • Boller T.
      • Felix G.
      A renaissance of elicitors: perception of microbe-associated molecular patterns and danger signals by pattern-recognition receptors..
      ). An activated plant triggered immunity in a plant cell may cause localized death (
      • Jones J.D.
      • Dangl J.L.
      The plant immune system..
      ), an oxidative burst of reactive oxygen species to signal neighboring cells of invasion (
      • Freeman B.C.
      • Beattie G.A.
      An overview of plant defenses against pathogens and herbivores.
      ), a rapid fluctuation in the calcium gradient to signal that a pathogen has been detected (
      • DeFalco T.A.
      • Bender K.W.
      • Snedden W.A.
      Breaking the code: Ca2+ sensors in plant signalling..
      ), release of pathogenesis related enzymes including chitinase, to degrade fungal chitin (
      • Sexton A.C.
      • Howlett B.J.
      Parallels in fungal pathogenesis on plant and animal hosts..
      ), activation of enzymes to strength the cell wall, activation of defense genes, and induction of phytoalexins, which are antimicrobial substance synthesized de novo (
      • Knogge W.
      Fungal infection of plants..
      ).

      Disease in WPCS

      Fungi can also attack the plant material in storage. To limit the growth and colonization, generally, it is recommended to store corn material in dry conditions and as mature crops (
      • Richard J.L.
      Some major mycotoxins and their mycotoxicoses—An overview..
      ). The occurrence of fungi in silages usually is the result of poor sealing and poor compaction causing aerobic conditions in the silo, not only causing losses of feed but also reductions in palatability (
      • Pahlow G.
      • Muck R.
      • Driehuis F.
      • Oude Elferink S.J.W.H.
      • Spoelstra S.F.
      Microbiology of ensiling.
      ). Furthermore, visibly molded areas of silages underestimate the amount of fungi within the silage content, as well as the high probability of mycotoxins (
      • Pahlow G.
      • Muck R.
      • Driehuis F.
      • Oude Elferink S.J.W.H.
      • Spoelstra S.F.
      Microbiology of ensiling.
      ).
      Fungal disease on corn plants ensiled as WPCS can affect the nutritional content within the plant material. Inoculation of northern leaf blight, caused by the fungus Exserohilum turcicum, on corn plants increased the NDF (from 39.2 ± 3.2% to 49.9 ± 4.1% of DM) and ADF (from 21.7 ± 3.0% to 26.3 ± 3.2% of DM) concentrations compared with nondiseased corn plants (
      • Wang P.
      • Souma K.
      • Kobayashi Y.
      • Iwabuchi K.
      • Sato C.
      • Masuko T.
      Influences of Northern Leaf Blight on corn silage fermentation quality, nutritive value and feed intake by sheep..
      ). Dry matter digestibility was less for sheep consuming WPCS from diseased corn plants (0.665 ± 0.029) compared with control (0.725 ± 0.012), measured using metabolic crates (
      • Wang P.
      • Souma K.
      • Kobayashi Y.
      • Iwabuchi K.
      • Sato C.
      • Masuko T.
      Influences of Northern Leaf Blight on corn silage fermentation quality, nutritive value and feed intake by sheep..
      ). Yet, DMI was not different for sheep consuming WPCS from diseased corn plants (3.46 ± 0.41% of BW0.75/d) compared with control (4.09 ± 0.41% of BW0.75/d;
      • Wang P.
      • Souma K.
      • Kobayashi Y.
      • Iwabuchi K.
      • Sato C.
      • Masuko T.
      Influences of Northern Leaf Blight on corn silage fermentation quality, nutritive value and feed intake by sheep..
      ).
      Fungal colonization on the corn plant causes a competition for nutrients between the plant and the fungus. The plant has many mechanisms (e.g., lignification and leaf shedding) to attempt to hinder the growth of the fungal infestation. These mechanisms may potentially decrease the digestibility of the plant (
      • Venancio W.S.
      • Rodrigues M.A.T.
      • Begliomini E.
      • De Souza N.L.
      Physiological effects of strobilurin fungicides on plants..
      ). The fungal infestation can change the chemical composition of the plant and compete for nutrients (
      • Venancio W.S.
      • Rodrigues M.A.T.
      • Begliomini E.
      • De Souza N.L.
      Physiological effects of strobilurin fungicides on plants..
      ).
      In another study, corn plants were ensiled with no fungi (no rust) or a medium concentration (all leaves on the lower half of the plant affected) or high concentration (all leaves affected) of southern rust, caused by the fungus Puccinia polysora, and then ensiled (
      • Queiroz O.C.
      • Kim S.
      • Adesogan A.
      Effect of treatment with a mixture of bacteria and fibrolytic enzymes on the quality and safety of corn silage infested with different levels of rust..
      ). Increasing the rust infestation from no rust to medium rust to high rust concentration on corn plants ensiled as WPCS increased concentrations of DM, NDF (no rust: 44.1% of DM, medium rust: 47.7% of DM, and high rust: 48.5% of DM), and ADF (no rust: 23.1% of DM, medium rust: 25.1% of DM, and high rust: 25.3% of DM) and decreased the in vitro DM true digestibility (no rust: 66.9%, medium rust: 63.2%, and high rust: 60.1%) and in vitro NDF digestibility (no rust: 38.1%, medium rust: 39.8%, and high rust: 36.2%) (
      • Queiroz O.C.
      • Kim S.
      • Adesogan A.
      Effect of treatment with a mixture of bacteria and fibrolytic enzymes on the quality and safety of corn silage infested with different levels of rust..
      ). Additionally, increased rust infestation on WPCS resulted in worse fermentation conditions exhibited by increased pH (no rust: 3.65, medium rust: 3.71, and high rust: 3.97) and decreased lactate (no rust: 4.99, medium rust: 4.02, and high rust: 2.28%). Aflatoxin was detected in WPCS from corn plants with a high concentration of southern rust at a concentration of 5.20 mg/kg of DM (
      • Queiroz O.C.
      • Kim S.
      • Adesogan A.
      Effect of treatment with a mixture of bacteria and fibrolytic enzymes on the quality and safety of corn silage infested with different levels of rust..
      ). Zearalenone was detected only in WPCS with no concentration of southern rust at a concentration of 0.64 mg/kg of DM (
      • Queiroz O.C.
      • Kim S.
      • Adesogan A.
      Effect of treatment with a mixture of bacteria and fibrolytic enzymes on the quality and safety of corn silage infested with different levels of rust..
      ).
      Other researchers evaluated the effects of physically damaging the ears of corn in the field before harvest on the production of mycotoxins and fermentation when ensiled as WPCS, to represent insect or hail damage on corn plants. In the first experiment, physical damage to corn kernels occurred at the milk stage of corn development (R3) by slashing a knife through the kernels (
      • Teller R.
      • Schmidt R.
      • Whitlow L.
      • Kung Jr., L.
      Effect of physical damage to ears of corn before harvest and treatment with various additives on the concentration of mycotoxins, silage fermentation, and aerobic stability of corn silage..
      ). Corn plants from the first experiment were ensiled as WPCS for 126 d. Physical damage to the corn ear resulted in an increased concentration of fumonisin B1 (8.50 mg/kg for damaged and 4.00 mg/kg for undamaged) and DON (3.12 mg/kg for damaged and 0.92 mg/kg for undamaged) but a decreased concentration of ZEA (1.03 mg/kg for damaged and 0.46 mg/kg for undamaged) in WPCS (
      • Teller R.
      • Schmidt R.
      • Whitlow L.
      • Kung Jr., L.
      Effect of physical damage to ears of corn before harvest and treatment with various additives on the concentration of mycotoxins, silage fermentation, and aerobic stability of corn silage..
      ). Neutral detergent fiber and ADF were not different for WPCS physically damaged (45.0 and 26.8% of DM for NDF and ADF, respectively) compared with undamaged (45.2 and 27.3% of DM for NDF and ADF, respectively). In the second study, physical damage to the corn kernels occurred either 27 or 9 d before harvest, and they were ensiled for 95 d. Damage to corn kernels 27 d prior (29.5% of DM) to harvest increased the ADF content in WPCS compared with 9 d prior (25.2% of DM) or no damage (25.7% of DM;
      • Teller R.
      • Schmidt R.
      • Whitlow L.
      • Kung Jr., L.
      Effect of physical damage to ears of corn before harvest and treatment with various additives on the concentration of mycotoxins, silage fermentation, and aerobic stability of corn silage..
      ). Whole-plant corn silage damaged 27 d before harvest resulted in an increased concentration of ADF (31.9% of DM) and NDF (48% of DM) when compared with WPCS from nondamaged ears (22.3 and 36.3% of DM for ADF and NDF, respectively;
      • Teller R.
      • Schmidt R.
      • Whitlow L.
      • Kung Jr., L.
      Effect of physical damage to ears of corn before harvest and treatment with various additives on the concentration of mycotoxins, silage fermentation, and aerobic stability of corn silage..
      ). Furthermore, WPCS from corn plants damaged 27 d before harvest resulted in an increased concentration of DON (14.77 mg/kg), fumonisin B1 (7.63 mg/kg), and ZEA (3.66 mg/kg) when compared with WPCS from undamaged corn kernels (0.18, 1.03, and 0.99 mg/kg for DON, fumonisin B1, and ZEA, respectively;
      • Teller R.
      • Schmidt R.
      • Whitlow L.
      • Kung Jr., L.
      Effect of physical damage to ears of corn before harvest and treatment with various additives on the concentration of mycotoxins, silage fermentation, and aerobic stability of corn silage..
      ).

      Environment

      A favorable environment is needed for the development of plant disease, completing the final side of the disease triangle. The favorable environment for one species of fungi may be different for another. For example, when growing conditions for corn plants include a warm ambient temperature and drought conditions, corn plants are more susceptible to the fungi A. flavus and A. parasiticus, which produce aflatoxin as a secondary metabolite (
      • Richard J.L.
      Some major mycotoxins and their mycotoxicoses—An overview..
      ). Yet, the foliar fungus E. turcicum, causing northern leaf blight in corn, favors cool and humid conditions for colonization of foliage (
      • Wise K.
      Diseases of Corn: Northern Corn Leaf Blight.
      ). Understanding the role of the complex relationship among plant cells, fungi, and the environment is crucial for the future production of corn and those whom consume it.
      According to
      • Wu F.
      • Bhatnagar D.
      • Bui-Klimke T.
      • Carbone I.
      • Hellmich R.
      • Munkvold G.
      • Paul P.
      • Payne G.
      • Takle E.
      Climate change impacts on mycotoxin risks in US maize..
      , aflatoxin and fumonisin concentrations in corn will likely increase, whereas DON concentrations will decrease if the current climate patterns continue in this century. Nonetheless, alterations in cropping patterns or shifts caused by climate change could create new opportunities for DON in areas where corn plants are scarcer. In Poland, a study reported that the concentrations of corn grain contaminated with ZEA and DON were low. One of the plausible explanations hypothesized by the authors for the aforementioned low concentrations was that mean and maximum temperatures during yield formation and grain ripening stages are usually lower than 25°C in Poland. Optimal temperatures for fumonisin biosynthesis are between 25 and 30°C (
      • Marin S.
      • Magan N.
      • Belli N.
      • Ramos A.J.
      • Canela R.
      • Sanchis V.
      Two-dimensional profiles of fumonisin B1 production by Fusarium moniliforme and Fusarium proliferatum in relation to environmental factors and potential for modelling toxin formation in maize grain..
      ), and DON is usually produced more rapidly at 25°C (
      • Ramirez M.L.
      • Reynoso M.M.
      • Farnochi M.C.
      • Chulze S.
      Vegetative compatibility and mycotoxin chemotypes among Fusarium graminearum (Gibberella zeae) isolates from wheat in Argentina..
      ).
      • Miller J.D.
      Factors that affect the occurrence of fumonisin..
      preconized that the best strategy available for lower risks of fumonisin in corn plants and grain is to guarantee that hybrids are adapted to the environment, to limit drought stress and insect herbivory. The author suggests that it may be necessary, in the future, to create hybrids that contain enzymes to degrade fumonisin as it is produced.

      Fungicides and Corn Plants

      Fungicide Classes and Mode of Action

      Countries around the world seek to control fungal pathogens through various methods, including fungicide application on plants, in hopes that chemical application will alleviate their effect on corn plants. In keeping with the disease triangle, fungicide’s aid in plant defense from fungal invasion. The Food and Agricultural Organization estimated in 2013 that Brazil applied the most fungicide on crops, using 40,000 t of active ingredients, followed by Mexico and then Spain, using 38,000 and 29,000 t of active ingredients, respectively (
      • FAO
      Inputs, Pesticide Use. Food Agric. Org. United Nations, FAOSTAT, Roma, Italy.
      ). In 2007 producers in the United States applied 20,000 t of active ingredients on crops (
      • FAO
      Inputs, Pesticide Use. Food Agric. Org. United Nations, FAOSTAT, Roma, Italy.
      ).
      Strobilurins fungicides, also known as QoI fungicides, are natural chemical structures isolated from the genera Strobilurus, in wood-rotting mushrooms. Because natural strobilurins break down quickly in UV light, synthetic analogs were developed for disease control (
      • Balba H.
      Review of strobilurin fungicide chemicals..
      ). Strobilurin fungicides are broad-spectrum fungicides, meaning the fungicide controls a wide array of fungal diseases in a variety of crops including cereals, fruits, vegetables, tree nuts, turf grasses, and ornamentals (
      • Vincelli P.
      Q o I (strobilurin) fungicides: Benefits and risks.
      ). Strobilurins bind to the quinol oxidation (Qo) site of cytochrome b. This binding stops the electron transport between cytochrome b and cytochrome c, stopping the oxidation of nicotinamide adenine dinucleotide and synthesis of ATP. Once on the waxy leaf surface, strobilurins move throughout the plant translaminarly, systemically, or both (
      • Vincelli P.
      Q o I (strobilurin) fungicides: Benefits and risks.
      ).
      A second group of fungicide commonly used today is carboxamide fungicides, also referred to as succinate dehydrogenase inhibitors. Within the succinate dehydrogenase inhibitor class of fungicides is the active ingredient fluxapyroxad. Succinate dehydrogenase inhibitors are broad-spectrum fungicides and can have translaminar or systemic activity within the host, depending on the pathogen and host (
      • McKay A.
      • Hagerty G.
      • Follas G.
      • Moore M.
      • Christie M.
      • Beresford R.
      Succinate dehydrogenase inhibitor (SDHI) fungicide resistance prevention strategy..
      ).
      A third group of fungicide is known as the demethylation inhibitors or sterol biosynthesis inhibitors, which contain the triazole fungicides. Within the triazole class is the active ingredient metconazole. Demethylation inhibitor fungicides are systemic (
      • Lepesheva G.I.
      • Waterman M.R.
      Sterol 14α-demethylase cytochrome P450 (CYP51), a P450 in all biological kingdoms..
      ) and single-site specific inhibitors commonly used on cereal grain (
      • Lucas J.A.
      • Hawkins N.J.
      • Fraaije B.A.
      Chapter Two—The evolution of fungicide resistance.
      ).

      Fungicide Application in Corn Plants

      In recent years, some researchers and chemical companies have concluded that foliar fungicide application on corn plants may increase yields even in the absence of disease (
      • Wise K.
      • Mueller D.
      Are fungicides no longer just for fungi? An analysis of foliar fungicide use in corn.
      ). In the US Corn Belt, several foliar diseases are of concern, depending on the production region, but GLS has been the disease of greatest concern since first becoming a problem in the 1980s and 1990s (
      • Lipps P.E.
      Gray leaf spot epiphytotic in Ohio corn..
      ). The elevation of GLS from a disease of secondary importance to a major problem throughout the eastern United States and the Midwest paralleled the adoption of reduced tillage (
      • Lipps P.E.
      Gray leaf spot epiphytotic in Ohio corn..
      ).
      In a meta-analysis on yield response and pyraclostrobin fungicide treatment, the mean difference in grain yield for plots treated with foliar fungicide increased 255.91 kg/ha compared with untreated plots (
      • Paul P.A.
      • Madden L.V.
      • Bradley C.A.
      • Robertson A.E.
      • Munkvold G.P.
      • Shaner G.
      • Wise K.A.
      • Malvick D.K.
      • Allen T.W.
      • Grybauskas A.
      • Vincelli P.
      • Esker P.
      Meta analysis of yield response of hybrid field corn to foliar fungicides in the U.S. corn belt..
      ). Authors concluded that when corn foliar disease (e.g., GLS) incidence in the field was less than 5%, the likelihood of an advantageous yield (i.e., bushels per acre) increase and beneficial physiological response from fungicide application was minimal and not enough to be able to cover the costs of the application. However, when disease incidence in the field was greater than 5%, fungicide application was more likely to lead to a return in profit due to increased corn grain yield. Furthermore, in a consecutive 2-yr study,
      • Bradley C.
      • Ames K.
      Effect of foliar fungicides on corn with simulated hail damage..
      did not report an increase in grain yield in 2008, under low disease severity environments, but in 2007 did report a grain yield increase when under higher disease severity. Routine scouting for disease in the cornfield is crucial for determining when fungicide application will be most profitable.
      When a producer’s field is diseased, proper timing of fungicide application on the plant may also provide beneficial results. Under pressure from fungal disease, application of pyraclostrobin (Headline, BASF Corp., Florham Park, NJ) on corn plants at the vegetative stage increased grain yield by 550 kg/ha compared with untreated fields of corn plants (
      • Nelson K.A.
      • Meinhardt C.
      Foliar boron and pyraclostrobin effects on corn yield..
      ). But others (
      • Mueller D.
      • Pope R.
      Corn Field Guide.
      ;
      • Wright P.
      • Parker M.
      • Van Tilburg R.
      • Hedderley D.
      Effect of planting dates and azoxystrobin fungicide application regimes on common rust of maize..
      ) have reported earlier applications to be beneficial as well. In a year with high incidence of common rust, foliar fungicide applied as a preventative at V6 increased corn grain yield by 362.9 kg/ha compared with application at before tassel, when 6% of the total leaf area was diseased (
      • Wright P.
      • Parker M.
      • Van Tilburg R.
      • Hedderley D.
      Effect of planting dates and azoxystrobin fungicide application regimes on common rust of maize..
      ). Yet, in a different year of the same study, when disease incidence was low, foliar fungicide applied as a preventative at V6 did not increase corn grain yield when compared with application at tassel (
      • Wright P.
      • Parker M.
      • Van Tilburg R.
      • Hedderley D.
      Effect of planting dates and azoxystrobin fungicide application regimes on common rust of maize..
      ).
      Fungicide applications on corn plants can improve the nutrients within the plant material. In 2007 the University of Wisconsin reported a possible trend for a 1 percentage unit decrease (40.6 vs. 39.6%) in NDF concentration when comparing WPCS from corn plants treated with foliar fungicide with untreated corn plants (
      • Blonde G.
      • Esker P.
      The effect of Headline foliar fungicide on corn silage yield and quality.
      ). On a DM basis, the average yield was 9.2 t of DM per hectare and 0.7 t of DM per hectare more (+9%) for treated areas. The increased WPCS DM yield per hectare for corn plants treated with fungicide could have caused a dilution effect of NDF (
      • Blonde G.
      • Esker P.
      The effect of Headline foliar fungicide on corn silage yield and quality.
      ).
      • Yates I.E.
      • Bacon C.W.
      • Hinton D.M.
      Effects of endophytic infection by Fusarium moniliforme on corn growth and cellular morphology..
      proposed that when a corn plant had fungal infestation of the root, the structural components and rigidity increased, which the authors attributed to the plant attempting to decrease further infestation into the upper portion of the plant by increasing the structurally rigid components of the plant such as lignin.
      Furthermore, a study at the University of Illinois evaluated the effects of fungicide application on the physical and nutritional content of corn plant leaves, ears, stalks, and flag leaves (
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application effects on plant composition of a silage variety corn..
      ). Fungicide applications on corn plants during the summer of 2015 were as follows: control (CON), corn receiving no foliar fungicide application; treatment 1 (V5), where corn plants received a mixture of pyraclostrobin and fluxapyroxad (PYR+FLUX) foliar fungicide at V5; treatment 2 (V5+R1), where corn plants received 2 applications of foliar fungicide, a mixture of PYR+FLUX at V5 and a mixture of pyraclostrobin + metconazole (PYR+MET) foliar fungicide at corn reproductive stage 1 (R1); treatment 3 (R1), in which corn plants received one application of PYR+MET foliar fungicide at R1. Corn plants with fungicide treatment were taller compared with untreated (2.7, 2.9, 3.0, and 2.9 m for CON, V5, V5+R1, and R1). Corn leaves in V5+R1 and in R1 had less yellow lower leaves than in CON and V5 (0.85, 0.77, 0.42, and 0.44 leaves for CON, V5, V5+R1, and R1, respectively). Corn stalks in V5+R1 had greater lignin concentration compared with CON and R1 (4.6, 5.6, 6.4, and 5.0% of DM for CON, V5, V5+R1, and R1). Corn leaves in V5+R1 had lower ADF and NDF concentrations (28.3 and 52.4% for ADF and NDF, respectively) compared with leaves in CON (33.3 and 56.9% for ADF and NDF, respectively;
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application effects on plant composition of a silage variety corn..
      ).
      Additionally, the group determined the effects of foliar fungicide (FUN; Headline AMP; BASF Corp., applied at vegetative tassel growth stage) and ensiling time (0, 30, 90, and 150 d) on fiber composition of 2 corn varieties [brown midrib (BMR) and floury (FLY);
      • Hollis M.E.
      • Pate R.T.
      • Mideros S.
      • Fellows G.M.
      • Akins M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide application effects on whole plant BMR and floury corn varieties, and whole-plant corn silage composition..
      ]. Treatments were assigned to sixteen 3.38-ha plots in a completely randomized split-plot block design. Treatments were BMR without FUN, FLY without FUN, BMR with FUN, and FLY with FUN. Samples of whole corn plants were collected and separated into leaves, stalks, flag leaf, and cobs. Corn plants in CON exhibited greater incidence of GLS disease than FUN corn plants with 6.52 and 1.75 ± 0.16% of leaf area, respectively. Corn plants in CON exhibited greater incidence of ear leaf injury than FUN with 2.74 and 0.72 ± 0.13% of leaf area, respectively. Corn plants in CON exhibited greater incidence of ear leaf injury at one leaf below the highest ear leaf compared with FUN with at 3.97 and 1.22 ± 0.17%, respectively. Brown midrib corn plants had a greater number of green leaves than FLY with 11.81 and 11.34 ± 0.09 leaves, respectively. Corn plants in control (BMR without FUN and FLY without FUN) had a greater number of yellow leaves than FUN corn plants with 0.28 and 0.08 ± 0.02, respectively. Corn plants treated with FUN were heavier (737 ± 18 g) than control corn plants (672 ± 18 g).
      Most recently, our group determined the effects of cut height at harvest and foliar fungicide application on BMR WPCS yield, chemical composition, and in situ degradability (
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      ). Foliar fungicide (prothioconazole and trifloxystrobin; Delaro, Bayer Crop Science, Monheim am Rhein, Germany) treatments were randomly assigned to one of sixteen 0.21-ha plots as follows: control (CON), plants received no application; treatment 1 (V5), plants received one application at corn vegetative stage 5 (V5); treatment 2 (V5R1), plants received 2 applications at V5 and corn reproductive stage 1 (R1); treatment 3 (R1), plants received one application at R1. At R5, corn plants in R1 and V5R1 had less yellow leaves (0.35 and 0.47 ± 0 0.19, respectively) than CON and V5 (0.63 and 1.08 ± 0.19, respectively). Disease prevalence was recorded as percentage of the total individual plant infected. Fungicide application had no effect on disease prevalence (1.62, 1.07, 1.23, 1.48 ± 0.30% for CON, V5, V5R1, and R1, respectively). There was no effect of fungicide treatment or cut height on the degradability of OM, NDF, or ADF. Raising the cut height from low cut (30.5 cm) to high cut (55.9 cm) increased the effective degradability of DM (0.565 and 0.577 ± 0.01, respectively), CP (0.565 and 0.576 ± 0.01, respectively), and starch (0.825 and 0.847 ± 0.01, respectively). Independently of corn variety, disease pressure, and fungicide active ingredient, corn plants seemed to have positively responded to fungicide application.
      Nonetheless, it is important to highlight that miss use of fungicide can result in fungicide resistance. The Fungicide Resistance Action Committee (
      • FRAC (Fungicide Resistance Action Committee)
      List of plant pathogenic organisms resistant to disease control agents.
      ; CropLife International, Bruxelles, Brussels) has determined that quinone outside inhibitors (QoI; strobilurins) fungicides pose a high risk of resistance development, and over 30 fungal pathogen species across 20 genera have been reported to show field resistance toward QoI fungicides. Preventing resistance should involve choosing a resistant corn hybrid, scouting fields regularly, implementing crop rotation, mixing and rotating fungicide classes, and following label recommendations. A proactive fungicide application (i.e., before the disease can be seen when scouting) could have a positive effect on plant health due to the time between the initial infection and symptom appearance. For instance, GLS has a 2-wk latent period from infection to considerable amounts of lesion formation (
      • Wise K.
      • Mueller D.
      Are fungicides no longer just for fungi? An analysis of foliar fungicide use in corn.
      ).

      Fungicide on Corn Ensiled as WPCS

      Researchers at the University of Wisconsin applied pyraclostrobin on corn plants and ensiled it as WPCS. Using the WPCS Milk2006 performance calculator from the University of Wisconsin–Madison extension (
      • Shaver R.
      • Lauer J.
      • Coors J.
      • Hoffman P.
      Dairy Nutrition Spreadsheets. Milk2006 Corn Silage: Calculates TDN-1x, NEL-3x, Milk per Ton, and Milk per Acre. Univ. Wisconsin, Madison, WI.
      ), which predicts the amount of milk to be produced if the WPCS were to be fed to cows, pyraclostrobin application on corn plants numerically increased projected milk production by 37 kg of milk/t of DM (75 lb milk/ton of DM) when compared with control (
      • Blonde G.
      • Esker P.
      The effect of Headline foliar fungicide on corn silage yield and quality.
      ).
      As previously mentioned,
      • Haerr K.J.
      • Lopes N.M.
      • Pereira M.N.
      • Fellows G.M.
      • Cardoso F.C.
      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
      fed mid-lactation cows WPCS from corn plants with either 0, 1, 2, or 3 applications of foliar fungicide. A decreasing linear relationship was reported for the number of fungicide applications and DMI (23.8, 23.0, 19.5, and 21.3 kg/d for CON, 1X, 2X, and 3X, respectively), but milk production was constant among treatments (34.5, 34.5, 34.2, and 34.3 kg/d, for CON, 1X, 2X, and 3X, respectively;
      • Haerr K.J.
      • Lopes N.M.
      • Pereira M.N.
      • Fellows G.M.
      • Cardoso F.C.
      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
      ). Therefore, cows fed WPCS from corn plants treated with foliar fungicide tended to have better feed efficiency measured as milk yield/DMI (1.46, 1.47, 1.70, and 1.70 kg/kg, for CON, 1X, 2X, and 3X, respectively), 3.5% FCM (1.47, 1.51, 1.71, and 1.73, for CON, 1X, 2X, and 3X, respectively), and ECM (1.43, 1.46, 1.66, and 1.69 for CON, 1X, 2X, and 3X, respectively;
      • Haerr K.J.
      • Lopes N.M.
      • Pereira M.N.
      • Fellows G.M.
      • Cardoso F.C.
      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
      ). The authors hypothesized that improved feed efficiency occurred because WPCS from corn plants treated with foliar fungicide application may have had increased nutritive quality compared with untreated WPCS.
      • Haerr K.J.
      • Pineda A.
      • Lopes N.M.
      • Weems J.D.
      • Bradley C.A.
      • Pereira M.N.
      • Murphy M.R.
      • Fellows G.M.
      • Cardoso F.C.
      Effects of corn treated with foliar fungicide on in situ corn silage degradability in Holstein cows..
      reported that application of fungicide on corn plants and then ensiled as WPCS (same treatments as in
      • Haerr K.J.
      • Lopes N.M.
      • Pereira M.N.
      • Fellows G.M.
      • Cardoso F.C.
      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
      ) resulted in higher DM degradable fraction, which increased with the number of fungicide applications. It tended to linearly decrease DM solubility. The authors reported that the soluble fraction of NDF and ADF decreased linearly with fungicide applications.
      • Kalebich C.C.
      From field to rumen: Foliar fungicide application on corn and its effects on the corn plant, corn silage, and Holstein cow performance.
      fed cows WPCS from corn plants with 0, 1, 2, or 3 applications of fungicide. Treatments were as follows: control (CON), WPCS with no application of foliar fungicide; treatment 1 (V5), WPCS received one application of pyraclostrobin and fluxapyroxad (PYR+FLUX) foliar fungicide at corn vegetative stage 5 (V5; when the emergence of the fifth leaf is visible); treatment 2 (V5/V8), WPCS received one application of PYR+FLUX at corn stage V5 plus another application of PYR+FLUX at corn stage vegetative stage 8 (V8; when the emergence of the eighth leaf is visible); and treatment 3 (V5/V8/R1), WPCS received one application of PYR+FLUX at corn stage V5, one application of PYR+FLUX at corn stage V8, plus a third application of pyraclostrobin and metconazole (PYR+MET) foliar fungicide at corn stage reproductive stage 1 (R1; when the silks are fully extended). No differences in DMI, milk yield, or feed efficiency were reported among treatments. However, cows in V5 compared with cows in V5/V8 tended to produce more 3.5% FCM (32.42 and 28.58 kg/d, respectively) and ECM (31.35 and 27.76 kg/d, respectively). Furthermore, concentration of milk lactose tended to be greater for cows fed WPCS treated with foliar fungicide when compared with CON (4.63, 4.77, 4.76, and 4.72% for CON, V5, V5/V8, and V5/V8/R1, respectively). The authors hypothesized that WPCS from corn plants with fungicide application may improve the digestibility compared with untreated WPCS (
      • Kalebich C.C.
      From field to rumen: Foliar fungicide application on corn and its effects on the corn plant, corn silage, and Holstein cow performance.
      ).
      As a follow-up study to evaluate the effects of fungicide on fermentation and composition of WPCS,
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      prepared 0.9-kg laboratory silos of treatment chopped corn plants material. Fungicide applications on corn plants during the summer of 2015 were as follows: control (CON), corn plants received no foliar fungicide application; treatment 1 (V5), where corn plants received a mixture of pyraclostrobin and fluxapyroxad (PYR+FLUX) foliar fungicide at V5; treatment 2 (V5+R1), where corn plants received 2 applications of foliar fungicide, a mixture of PYR+FLUX at V5 and a mixture of pyraclostrobin + metconazole (PYR+MET) foliar fungicide at corn reproductive stage 1 (R1); treatment 3 (R1), in which corn plants received one application of PYR+MET foliar fungicide at R1. Fungicide-treated WPCS had decreased DM (33.5, 31.9, 31.5, and 31.7% of DM for CON, V5, V5+R1, and R1, respectively) but increased CP (8.1, 8.5, 8.2, and 8.7% of DM for CON, V5, V5+R1, and R1, respectively), water-soluble carbohydrates (3.8, 4.0, 4.6, and 5.2% of DM for CON, V5, V5+R1, and R1, respectively), and lactic acid concentration (4.65, 5.01, 5.09, and 5.50% of DM for CON, V5, V5+R1, and R1, respectively). Whole-plant corn silage in R1 had a lower lignin concentration (2.4, 2.4, 2.6, and 2.0% of DM for CON, V5, V5+R1, and R1, respectively), and WPCS in V5 had more kilograms of milk per tonne of DM (1,511, 1,631, 1,585, and 1,576 kg/t of DM for CON, V5, V5+R1, and R1, respectively). Whole-plant corn silage from corn plants with fungicide application may enhance the nutritive and fermentative profile for ruminants (
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      ).
      • Hollis M.E.
      • Pate R.T.
      • Mideros S.
      • Fellows G.M.
      • Akins M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide application effects on whole plant BMR and floury corn varieties, and whole-plant corn silage composition..
      collected fresh-cut WPCS at harvest and sealed it inside mini silos (0, 30, 90, and 150 d ensiled). Whole-plant corn silage in CON resulted in greater DM and DM yield than WPCS from corn plants treated with fungicide (FUN). Interestingly, on an as-fed basis, corn plants treated with FUN tended to yield more WPCS than CON with 63,634 and 60,488 ± 1,533 kg/ha, respectively. A variety-by-treatment interaction was observed for kernel vitreousness score with scores of 3.23, 2.99, 2.49, and 2.80 ± 0.14 for BMR/CON, BMR/FUN, FLY/CON, and FLY/FUN, respectively. The BMR corn plants treated with FUN and ensiled for 90 to 150 d seemed to be the best WPCS for feeding dairy cows due to its potential to be converted into milk (Milk2006;
      • Shaver R.
      • Lauer J.
      • Coors J.
      • Hoffman P.
      Dairy Nutrition Spreadsheets. Milk2006 Corn Silage: Calculates TDN-1x, NEL-3x, Milk per Ton, and Milk per Acre. Univ. Wisconsin, Madison, WI.
      ).
      Most recently,
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      reported that fungicide application had no effect on BMR WPCS DM, gross yield, or DM yield, but ensiled in mini silos over time (90 d), fungicide-treated corn plants had increased VFA scores, lactic acid, acetic acid, and total acid concentrations compared with BMR corn plants not treated with fungicide (CON). It seemed that foliar fungicide application on BMR corn created a better fermentation environment for corn plants ensiled as WPCS, as fungicide-treated corn plants ensiled over time had higher VFA scores, lactic acid, acetic acid, and total acid concentrations. Data for WPCS from all published experiments completed in our group were evaluated using Milk2006 (
      • Shaver R.
      • Lauer J.
      • Coors J.
      • Hoffman P.
      Dairy Nutrition Spreadsheets. Milk2006 Corn Silage: Calculates TDN-1x, NEL-3x, Milk per Ton, and Milk per Acre. Univ. Wisconsin, Madison, WI.
      ) and summarized in Table 3 and Figure 1.
      Table 3Experiments [whole-plant corn silage (WPCS) sample no.] from which data were used to examine the association of WPCS nutritional value with potential for milk production
      WPCS

      sample no.
      Whole-plant corn silage sample from a determined experiment.
      Year of

      harvest
      Corn hybrid
      BMR = brown midrib.
      Treatment
      Experimental treatment applied to corn plants. FUNV5 = fungicide applied at corn-plant stage of growth V5 (vegetative stage 5); FUN2X = fungicide applied at corn-plant stages of growth V5 and R1 (any silk visible on the cob); FUN3X = fungicide applied at corn-plant stages of growth V5, R1, and R3 (kernels are yellow with milky white fluid); CON = no application of fungicide; FUNV5V8 = fungicide applied at corn-plant stages of growth V5 and V8 (vegetative stage 8); FUNV5V8R1 = fungicide applied at corn-plant stages of growth V5, V8, and R1; FUNV5R1 = fungicide applied at corn-plant stages of growth V5 and R1; FUNR1 = fungicide applied at corn-plant stage of growth R1; CONLC = no application of fungicide and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; FUNV5LC = fungicide applied at corn-plant stage of growth V5 and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; FUNV5R1LC = fungicide applied at corn-plant stages of growth V5 and R1 and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; FUNR1LC = fungicide applied at corn-plant stage of growth R1 and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; CONHC = no application of fungicide and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil; FUNV5HC = fungicide applied at corn-plant stage of growth V5 and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil; FUNV5R1HC = fungicide applied at corn-plant stages of growth V5 and R1 and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil; FUNR1HC = fungicide applied at corn-plant stage of growth R1 and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil.
      Foliar

      disease,
      Disease evaluations were conducted before each fungicide treatment and before harvest. Ten random plants from each of the plots were evaluated. The same evaluator conducted all evaluations to minimize error.
      %
      DM, %DM yield,

      t/ha
      NDFD30,
      A 30-h in vitro digestion of NDF was conducted in buffered rumen fluid (NDFD30) using procedures described in detail by Kruse et al. (2010) and Coblentz et al. (2017) using the Ankom Daisy batch culture system.


      % NDF
      Reference
      Reference for complete description of the experimental design and treatments.
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      22013ConventionalFUN2X034.4119.9849
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      32013ConventionalFUN3X030.3716.8548.82
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      42013ConventionalCON030.6316.9950.09
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      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
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      From field to rumen: Foliar fungicide application on corn and its effects on the corn plant, corn silage, and Holstein cow performance.
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      From field to rumen: Foliar fungicide application on corn and its effects on the corn plant, corn silage, and Holstein cow performance.
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      • Kalebich C.C.
      From field to rumen: Foliar fungicide application on corn and its effects on the corn plant, corn silage, and Holstein cow performance.
      82014ConventionalFUNV5V8R1031.8422.4151.2
      • Kalebich C.C.
      From field to rumen: Foliar fungicide application on corn and its effects on the corn plant, corn silage, and Holstein cow performance.
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      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      102015ConventionalFUNV52131.924.0148.3
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
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      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      112015ConventionalFUNV5R13.4431.523.2249.3
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      • Robinson K.N.
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      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      122015ConventionalFUNR11.6331.723.8350.5
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
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      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      132016BMRCON2032.118.8559.3
      • Hollis M.E.
      • Pate R.T.
      • Mideros S.
      • Fellows G.M.
      • Akins M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide application effects on whole plant BMR and floury corn varieties, and whole-plant corn silage composition..
      142016BMRFUNR1530.718.9260
      • Hollis M.E.
      • Pate R.T.
      • Mideros S.
      • Fellows G.M.
      • Akins M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide application effects on whole plant BMR and floury corn varieties, and whole-plant corn silage composition..
      152016FlouryCON1933.519.0147.8
      • Hollis M.E.
      • Pate R.T.
      • Mideros S.
      • Fellows G.M.
      • Akins M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide application effects on whole plant BMR and floury corn varieties, and whole-plant corn silage composition..
      162016FlouryFUNR15.2533.520.5549.1
      • Hollis M.E.
      • Pate R.T.
      • Mideros S.
      • Fellows G.M.
      • Akins M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide application effects on whole plant BMR and floury corn varieties, and whole-plant corn silage composition..
      172017BMRCONLC1.6234.213.7454
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      182017BMRFUNV5LC1.0732.512.3755.9
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      192017BMRFUNV5R1LC1.2332.712.1054
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      202017BMRFUNR1LC1.4832.712.0453.8
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      212017BMRCONHC1.6235.112.4456.8
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      222017BMRFUNV5HC1.0733.211.6856.1
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      232017BMRFUNV5R1HC1.2333.511.4360.5
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      242017BMRFUNR1HC1.483411.6358.5
      • Damery T.A.
      From field to feed: The effects of fungicide application and cutting height on the quality and in situ degradability of corn ensiled as whole-plant corn silage.
      1 Whole-plant corn silage sample from a determined experiment.
      2 BMR = brown midrib.
      3 Experimental treatment applied to corn plants. FUNV5 = fungicide applied at corn-plant stage of growth V5 (vegetative stage 5); FUN2X = fungicide applied at corn-plant stages of growth V5 and R1 (any silk visible on the cob); FUN3X = fungicide applied at corn-plant stages of growth V5, R1, and R3 (kernels are yellow with milky white fluid); CON = no application of fungicide; FUNV5V8 = fungicide applied at corn-plant stages of growth V5 and V8 (vegetative stage 8); FUNV5V8R1 = fungicide applied at corn-plant stages of growth V5, V8, and R1; FUNV5R1 = fungicide applied at corn-plant stages of growth V5 and R1; FUNR1 = fungicide applied at corn-plant stage of growth R1; CONLC = no application of fungicide and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; FUNV5LC = fungicide applied at corn-plant stage of growth V5 and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; FUNV5R1LC = fungicide applied at corn-plant stages of growth V5 and R1 and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; FUNR1LC = fungicide applied at corn-plant stage of growth R1 and corn plant chopped at 30.5 cm (low cut; 12 in) from the soil; CONHC = no application of fungicide and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil; FUNV5HC = fungicide applied at corn-plant stage of growth V5 and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil; FUNV5R1HC = fungicide applied at corn-plant stages of growth V5 and R1 and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil; FUNR1HC = fungicide applied at corn-plant stage of growth R1 and corn plant chopped at 55.9 cm (high cut; 22 in) from the soil.
      4 Disease evaluations were conducted before each fungicide treatment and before harvest. Ten random plants from each of the plots were evaluated. The same evaluator conducted all evaluations to minimize error.
      5 A 30-h in vitro digestion of NDF was conducted in buffered rumen fluid (NDFD30) using procedures described in detail by
      • Kruse K.A.
      • Combs D.K.
      • Esser N.M.
      • Coblentz W.K.
      • Hoffman P.C.
      Evaluation of potential carryover effects associated with limit feeding gravid Holstein heifers..
      and
      • Coblentz W.K.
      • Akins M.S.
      • Cavadini J.S.
      • Jokela W.E.
      Net effects of nitrogen fertilization on the nutritive value and digestibility of oat forages..
      using the Ankom Daisy batch culture system.
      6 Reference for complete description of the experimental design and treatments.
      Figure 1
      Figure 1(A) Whole-plant corn silage (WPCS) from different experiments (WPCS sample no.) indicated in from which data were used in Milk2006 (
      • Shaver R.
      • Lauer J.
      • Coors J.
      • Hoffman P.
      Dairy Nutrition Spreadsheets. Milk2006 Corn Silage: Calculates TDN-1x, NEL-3x, Milk per Ton, and Milk per Acre. Univ. Wisconsin, Madison, WI.
      ) to examine the association of WPCS nutritional value with potential for milk (kg) per tonne of WPCS DM. (B) Whole-plant corn silage from different experiments (WPCS sample no.) indicated in from which data were used in Milk2006 (
      • Shaver R.
      • Lauer J.
      • Coors J.
      • Hoffman P.
      Dairy Nutrition Spreadsheets. Milk2006 Corn Silage: Calculates TDN-1x, NEL-3x, Milk per Ton, and Milk per Acre. Univ. Wisconsin, Madison, WI.
      ) to examine the association of WPCS nutritional value with potential for milk (kg) per hectare of corn plant harvested.

      Mycotoxin and Fungicides

      Fungicides have been tested for preventing fungal colonization and mycotoxin contamination in cereal grains. Results of studies have been conflicting in their ability to control mycotoxin concentration within crops. Authors reported mycotoxin presence in WPCS samples without visual observation of fungus noted in the corn plants in the field (
      • Haerr K.J.
      The use of corn treated with various applications of foliar fungicide to increase corn silage quality and performance of Holstein cows in animal sciences.
      ). Interestingly, a study done by
      • Eckard S.
      • Wettstein F.E.
      • Forrer H.-R.
      • Vogelgsang S.
      Incidence of Fusarium species and mycotoxins in silage maize..
      concluded that when corn plants were diagnosed visually, only 1 to 3% of corn plants showed signs of infection on the surface; however, when the corn particles were plated, it was found that the average Fusarium incidence was 46%. Corn plants harvested by
      • Haerr K.J.
      • Lopes N.M.
      • Pereira M.N.
      • Fellows G.M.
      • Cardoso F.C.
      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
      ;
      • Haerr K.J.
      The use of corn treated with various applications of foliar fungicide to increase corn silage quality and performance of Holstein cows in animal sciences.
      ) could have been infected, even though visual symptoms were not present. Applications of metconazole and tebuconazole, another active ingredient of fungicide, reduced concentrations of DON mycotoxin and head blight in winter wheat more than applications of azoxystrobin, another active ingredient (
      • Edwards S.
      • Pirgozliev S.
      • Hare M.
      • Jenkinson P.
      Quantification of trichothecene-producing Fusarium species in harvested grain by competitive PCR to determine efficacies of fungicides against Fusarium head blight of winter wheat..
      ). However, researchers hypothesized fungicides act as an additional stress factor for the fungus and stimulate mycotoxins as a defense mechanism (
      • Magan N.
      • Hope R.
      • Colleate A.
      • Baxter E.
      Relationship between growth and mycotoxin production by Fusarium species, biocides and environment.
      ).
      Some toxigenic fungal species that may affect plants before and after harvest are Penicillium nordicum and Penicillium verrucosum (
      • Schmidt-Heydt M.
      • Stoll D.
      • Geisen R.
      Fungicides effectively used for growth inhibition of several fungi could induce mycotoxin biosynthesis in toxigenic species..
      ). These penicillia are able to produce the mycotoxins ochratoxin and citrinin (
      • Schmidt-Heydt M.
      • Stoll D.
      • Geisen R.
      Fungicides effectively used for growth inhibition of several fungi could induce mycotoxin biosynthesis in toxigenic species..
      ). Both toxins have polyketide backbones and are structurally highly related. Ochratoxin A as well as citrinin are mainly nephrotoxic and hepatotoxic and may act synergistically (
      • Braunberg R.C.
      • Barton C.N.
      • Gantt O.O.
      • Friedman L.
      Interaction of citrinin and ochratoxin A..
      ). For ochratoxin A, which is rated as a class B carcinogen, regulatory limits have been set in several countries. The level of citrinin is not currently regulated. Penicillium verrucosum adapts its secondary metabolite profile depending on the environmental conditions (
      • Schmidt-Heydt M.
      • Graf E.
      • Stoll D.
      • Geisen R.
      The biosynthesis of ochratoxin A by Penicilliumas onemechanism for adaptation to NaCl rich foods..
      ). For example, oxidative stress usually induces defensive reactions such as radical scavenging mechanisms for reactive oxygen species.
      • Schmidt-Heydt M.
      • Stoll D.
      • Geisen R.
      Fungicides effectively used for growth inhibition of several fungi could induce mycotoxin biosynthesis in toxigenic species..
      reported that the biosynthesis of the mycotoxins ochratoxin A/B and citrinin were strongly induced when grown on malt extract glucose agar medium supplemented with the fungicide Rovral (Bayer Crop Science).
      Fungal contamination of WPCS can lead to DM loss, nutrient loss, and reduced palatability (
      • Alonso V.A.
      • Pereyra C.M.
      • Keller L.A.M.
      • Dalcero A.M.
      • Rosa C.A.R.
      • Chiacchiera S.M.
      • Cavaglieri L.R.
      Fungi and mycotoxins in silage: An overview..
      ). Foliar pathogens decrease the area of photosynthetic tissue, which reduces the transfer of assimilates to grain production by diverting assimilates to fungal growth, defense systems, and increased respiration (
      • Agrios G.N.
      Plant Pathology.
      ).
      • Whitlock L.A.
      • Wistuba T.J.
      • Seifers M.K.
      • Pope R.V.
      • Bolsen K.K.
      Effect of level of surface-spoiled silage on the nutritive value of corn silage diets..
      reported that feeding spoiled WPCS from the surface of a bunker silo depressed nutrient digestibility and DMI of steers.
      • Gerlach K.
      • Roß F.
      • Weiß K.
      • Buscher W.
      • Sudekum K.-H.
      Changes in maize silage fermentation products during aerobic deterioration and effects on dry matter intake by goats..
      fed spoiling silage to goats and reported negative correlations between ethyl-lactate and ethanol with DMI, but the strongest negative relationship with intake was from silage temperature. Application of fungicide in corn plants does not seem to have any effect on reducing molds responsible for WPCS aerobic deterioration (
      • Blonde G.
      • Esker P.
      The effect of Headline foliar fungicide on corn silage yield and quality.
      ;
      • Haerr K.J.
      • Lopes N.M.
      • Pereira M.N.
      • Fellows G.M.
      • Cardoso F.C.
      Corn silage from corn treated with foliar fungicide and performance of Holstein cows..
      ;
      • Kalebich C.C.
      • Weatherly M.E.
      • Robinson K.N.
      • Fellows G.M.
      • Murphy M.R.
      • Cardoso F.C.
      Foliar fungicide (pyraclostrobin) application on corn and its effects on corn silage composition..
      ). A variety of mycotoxins produced from fungi can be found in silages that are fed to dairy cattle (
      • Driehuis F.
      • Spanjer M.C.
      • Scholten J.M.
      • te Giffel M.C.
      Occurrence of mycotoxins in feedstuffs of dairy cows and estimation of total dietary intakes..
      ). Their presence is undesirable because they have the potential to induce negative effects on the health of animals (
      • Adesogan A.T.
      Mycotoxins in ensiled forages.
      ). Mycotoxins can accumulate on the plant in the field before harvest (
      • Doerr J.A.
      A little fresh air: Fungal toxins and silage.
      ), during storage, or during processing or feeding (
      • Whitlow L.W.
      • Hagler Jr, W.M.
      Mold and mycotoxin issues in dairy cattle: Effects, prevention and treatment.
      ).
      • Korosteleva S.N.
      • Smith T.K.
      • Boermans H.J.
      Effects of feed naturally contaminated with Fusarium mycotoxins on metabolism and immunity of dairy cows..
      reported that Fusarium mycotoxins decreased some cellular aspects of immune function in dairy cattle, while stimulating primary humoral response to specific antigens. The authors concluded that feeding of contaminated materials to dairy cows should be minimized. Recently,
      • Ferrero F.
      • Prencipe S.
      • Spadaro D.
      • Gullino M.L.
      • Cavallarin L.
      • Piano S.
      • Tabacco E.
      • Borreani G.
      Increase in aflatoxins due to Aspergillus section Flavi multiplication during the aerobic deterioration of corn silage treated with different bacteria inocula..
      demonstrated that improved WPCS aerobic stability (due to the inoculation of the chopped corn plant with Lactobacillus buchneri, Lactobacillus hilgardii, or both) reduced the risk of A. flavus outgrowth and aflatoxin production after WPCS opening. Nonetheless,
      • Charmley E.
      • Trenholm H.L.
      • Thompson B.K.
      • Vudathala D.
      • Nicholson J.W.G.
      • Prelusky D.B.
      • Charmley L.L.
      Influence of level of deoxynivalenol in the diet of dairy cows on feed intake, milk production, and its composition..
      reported that the inclusion of the mycotoxin DON in the diet of primiparous dairy cows yielding 20 to 25 kg/d milk, at up to 6 mg/kg of total diet DM over a 10-wk period, had no effect on volume of milk produced.

      Practical Economical Considerations

      • Paul P.A.
      • Madden L.V.
      • Bradley C.A.
      • Robertson A.E.
      • Munkvold G.P.
      • Shaner G.
      • Wise K.A.
      • Malvick D.K.
      • Allen T.W.
      • Grybauskas A.
      • Vincelli P.
      • Esker P.
      Meta analysis of yield response of hybrid field corn to foliar fungicides in the U.S. corn belt..
      calculated a 10-yr average corn grain price of $0.12/kg ($2.97/bushel) and application costs of $40 to $95/ha and showed that the probability of failing to recover the fungicide application cost (Ploss) for disease severity less than 5% was 0.55 to 0.98 for pyraclostrobin. However, when disease severity was greater than 5%, the corresponding probability was 0.36 to 0.95. They concluded that the high Ploss values found in most scenarios suggest that the use of these foliar fungicides is unlikely to be profitable when foliar disease severity is low and grain yield expectation is high (
      • Paul P.A.
      • Madden L.V.
      • Bradley C.A.
      • Robertson A.E.
      • Munkvold G.P.
      • Shaner G.
      • Wise K.A.
      • Malvick D.K.
      • Allen T.W.
      • Grybauskas A.
      • Vincelli P.
      • Esker P.
      Meta analysis of yield response of hybrid field corn to foliar fungicides in the U.S. corn belt..
      ).
      However, some value may be returned to producers by increasing the efficiency of converting feed to milk when feeding feedstuffs with fungicide application in the field to dairy. The section below will discuss data reported by
      • Haerr K.J.
      The use of corn treated with various applications of foliar fungicide to increase corn silage quality and performance of Holstein cows in animal sciences.
      but in an economic analysis. The total income from milk yield over feed costs was $7.35, $7.54, $8.31, and $7.83 for 0, 1, 2, or 3 applications of fungicide, respectively. Therefore, it seems cows fed WPCS from corn plants with fungicide treatment were more profitable than cows fed WPCS with no treatment. Additionally, even though the authors reported a positive linear effect for the number of fungicide applications and feed efficiency, the income over feed cost was not enough to offset the cost of a third fungicide application (~$30.00).

      On-Farm Evaluation

      Evaluating current on-farm practices and relaying those practices to the public is of paramount importance. Illinois dairy farms were evaluated in 2016 regarding corn plants fungal and toxin contamination in the field to understand how those issues are combated on farm along with management practices (
      • Weatherly M.
      Food safety through fungal disease and mycotoxin mitigation on dairy farms: From field to feed and the rumen.
      ). The survey was initially distributed to every dairy farmer on file (n = 635) as reported by the Illinois Milk Producers’ Association by way of mail on September 7, 2016, with an overall 22.7% return rate (n = 135). Not surprisingly, 58% of the respondents included WPCS between 30 to 60% in the lactation diet (% of DM) of their herd. Interestingly enough, 46% of the respondents did not scout or apply fungicide on corn plants for WPCS and 51% of the respondents had WPCS ensiled for no longer than 49 d (
      • Weatherly M.
      Food safety through fungal disease and mycotoxin mitigation on dairy farms: From field to feed and the rumen.
      ).

      APPLICATIONS

      It is well known that responsible applications of foliar fungicide on corn plants assist in limiting devastating losses in yield. Cows fed WPCS from corn plants with fungicide application improved feed efficiency and were more profitable than cows fed WPCS with no fungicide application. Whole-plant corn silage from corn plants with fungicide application reduced the fiber concentration and, therefore, improved its nutritive value. Additionally, corn plants treated with fungicide had an improved fermentation process during ensiling due to higher concentrations of lactic acid and sugar when compared with untreated corn plants. More research is needed to understand how fungus diversity and soil microbiology are affected by fungicide application. Cows around parturition (transition period) could potentially receive more benefit from WPCS from corn plants treated with fungicide than mid-lactating cows. However, the aforementioned hypothesis is still to be tested. Overall, fungicide application seems to be maximized when converted into feed (e.g., WPCS) and fed to dairy cattle.

      ACKNOWLEDGMENTS

      This project was partially supported by the USDA National Institute of Food and Agriculture (Washington, DC; NC-2042). Sincere appreciation is expressed to the Dairy Focus Team at the University of Illinois for assisting with data collection.

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