Phenotypic Trends Over Time for Performance of Centrally Tested Boars¹²

Performance data of 2769 boars evaluated in a central test station were analyzed to evaluate phenotypic trends from 1971 through 1987 for average daily gain (ADG), pen feed to gain ratio (FG), backfat thickness (BF), and longissimus muscle area (LMA). The study included data from Duroc, Hampshire, Spotted, and Yorkshire boars. Data from several other breed groups were analyzed as a single group (designated Other). All breed groups increased in ADG (linear year eHect, P<.05), averaging 953 gin 1971 vs. 1030 in 1987. Averaged over years, ADG was highest for Duroc and Yorkshire boars and lowest for Other boars. Feed/gain fluctuated over the study period, with a small net improvement (P<.1 0) from 1971 through 1987 for Yorkshire, Hampshire, and Other boars. The change in FG per year among Duroc and Spotted boars was nonsignificant. Averaged over years, FG ranged from 2.45 for Hampshire to 2.60 for Spotted boars. In all breeds, BF decreased from 1978 through 1981, followed by a period of several years with little change and then a slight increase the last 2 yr. These trends resulted in little difference between average BF in 1971 vs. 1987. Hampshire boars consistently had less BF than boars of other breed groups. Longissimus muscle area fluctuated with little net change for the entire evaluation period, although there appeared to be a slight upward trend among Hampshire boars from 1982 through 1987. Averaged over years, LMA ranged from 35.0 cm² for Yorkshire to 37.2 cm² for Hampshire boars. Boars tested in recent years in general gained faster, were similar in leanness and LMA, and in some breeds were slightly more efficient compared to boars tested in 1971.