EFFECTS OF COMPUDOSE(R) AND RUMENSIN(R), ALONE OR IN COMBINATION, ON THE GROWTH, AND CARCASS AND MEAT QUALITY OF STEERS FINISHED ON PASTURE

Rumensin(R) (monensin sodium) and Compudose(R) (oestradiol-17 beta) ca n both promote liveweight gain of pasture-fed cattle. Limited informat ion exists about their effects on carcass and meat quality characteris tics or their combined effects on beef cattle performance. This study examined the effects of Rumensin (R) and Compudose (C), alone and in c ombination, on the growth, carcass characteristics, and meat quality o f steers finished at pasture. Seventy-two yearling steers (290 +/- 4 k g) received either no treatment, R, C, or R+C for the 266-day experime ntal period. C led to increased liveweight gain (P < 0.001) but R had no effect and the R x C interaction was not significant. Weight-correc ted height was lower (P < 0.05) in Compudose-treated cattle. R had no significant effect on any carcass or meat quality traits and no intera ctions with C were found. Compudose treatment increased carcass weight (P < 0.001) and dressing-out percentage (P < 0.05), and decreased kid ney + pelvic fat weight (P < 0.005) and side length (P < 0.01). Compud ose decreased M. longissimus ultimate pH (P < 0.001) and increased mea t brightness L (P < 0.05), but Warner-Bratzler peak shear values were higher (P < 0.05) in meat of the C group. It is concluded that R has little effect on growth, or carcass or meat characteristics of steers at pasture, and that it has no influence on the way C affects these ch aracteristics.