Supplements, Parasite Treatments and Growth Implants for Brahman or English Crossbred Steers Grazing Endophyte-Infected or Noninfected Fescue in the Spring and Fall¹

Two experiments, each with a 2 × 3 × 2 × 2 factorial treatment arrangement and 96 beef steers, were conducted to determine the effects of crossbreed, grain supplement, parasite treatment and growth implant types on performance of steers grazing endophyte-infected (IF) or noninfected fescue (NF). In Exp. 1, Brahman and English crossbred steers (244 and 224 kg initial weights, respectively) grazing IF or NF paddocks for 84 d in the spring (mid-April to early July) received Ivomec® or Panacur® plus Warbex® and a grain supplement with or without activated carbons. Brahman crossbreds gained faster (P<.05) than did English crosses (.78 vs. .45 kg/d), and daily gain was greater (P<.05) for NF (.71 kg) than for IF (.51 kg). No effects of activated carbon supplementation or parasite treatment on daily gain were observed; interactions among the various factors were not significant. In Exp. 2, Brahman and English crossbred steers (330 and 275 kg initial weights, respectively; primarily those used in Exp. 1) grazing IF or NF paddocks in the fall for 84 d (late August to mid-November) were implanted with Ralgro® or Synovex® and were not supplemented or received (6 d/wk) 1.0% body weight/d of whole corn or .17% body weight/d (dry matter) of a mix of high-protein feeds (50% cottonseed meal, 37.5% corn gluten meal and 12.5% blood meal). Daily gain was similar (P<.23) for IF (.56 kg) and NF (.63 kg). Brahman crossbreds gained faster (P<.05) than did English cross steers. The improvement in daily gain with supplementation of Brahman crosses was greater than for English crossbreds and supplemental corn elevated daily gain of Brahman crossbreds more than did the protein mix, whereas the response of English crosses was similar for both supplement types (crossbred-supplement interaction; P<.05). Increases in daily gain were similar for both supplement types with Ralgro®, but with Synovex®, gain increased more with corn than with the protein mix (supplement-implant interaction; P<.05). Fescue and supplement type did not have a significant interaction. The different supplements, parasite treatments, growth implants and crossbreed types affected steer daily gain in spring and fall similarly with endophyte-infected and noninfected fescue.