EFFECT OF RUMINALLY UNDEGRADABLE PROTEIN FROM FISH-MEAL ON GROWTH ANDREPRODUCTION OF PERIPUBERTAL BRAHMAN BULLS

Thirty-nine Brahman bulls (301.7 +/- 4.1 d; 202.7 +/- 4.7 kg) were all otted to one of two treatments and fed soybean meal (SBM)- or fish mea l (FIS)-based supplements and hay to examine the effects of source of protein on growth and reproductive development. The fish meal suppleme nt had 72% ruminally undegradable protein (RUP) and the soybean meal s upplement had 47% RUP. Bulls assigned to the FIS treatment had higher (P < .01) total weight gain (81.2 +/- 1.4 vs 71.2 +/- 2.2 kg), higher (P < .01) ADG (.97 +/- .02 vs .85 +/- .03 kg), and better (P < .05) fe ed:gain ratio (7.6 +/- .1 vs 8.6 +/- .1 feed/BW gain for FIS vs SBM, r espectively). Age at first motile spermatozoa was not affected (P > .0 5) by source of protein (429.9 +/- 9.6 vs 427.2 +/- 9.5 d, for bulls r eceiving FIS or SBM supplements, respectively). Likewise, age at puber ty (473.3 +/- 21.7 d vs 465.9 +/- 12.9 d for bulls receiving FIS and S BM supplements, respectively) was similar for both treatment groups. T here were no differences between treatments in scrotal circumference a t those stages. At puberty semen quality was similar for bulls receivi ng FIS or SBM treatments, and no differences existed in LH and testost erone concentrations between treatments. We conclude that fish meal su pplement increased growth but did not alter reproductive parameters in Brahman bulls.