TESTICULAR AND EPIDIDYMAL FUNCTION DURING THE PERIPUBERAL PERIOD IN BRAHMAN BULLS RECEIVING VARIOUS AMOUNTS OF PROTEIN DEGRADABLE IN THE RUMEN

摘要

Thirty-nine Brahman bulls with an initial age and weight of 301.7+/-4.1 d and 202.7+/-4.7 kg, respectively, were randomly allocated to 1 of 2 dietary treatment groups within age, weight and sire in order to study the influence of source of protein and stage of peripuberal period on testicular and epididymal function. In the soybean meal treatment the amount of protein undegradable in the rumen averaged 47%, while it was 72% in the fish meal treatment. The supplements were isocaloric and isonitrogenous. Bulls were electroejaculated, and castrations were performed randomly in a predetermined order when the first ejaculate with the first motile sperm cells (Stage 1), 10 to 25 million (Stage 2), and 50 million or more sperm cells (Stage 3 - puberty) was obtained. Testicular and epididymal traits were analyzed for a single testicle and epididymis. Daily sperm production, daily sperm production per gram of testicular parenchyma, testicular weight and testicular parenchyma weight were not affected by treatment. Bulls receiving fish meal had heavier (P<0.01) epididymis than soybean meal-fed bulls (6.6+/-1.0 vs 3.9+/-0.6 g) but similar (P>0.05) epididymal sperm reserves. Daily sperm production(1 testicle) was 115.2+/-0.1, 447.4+/-0.1, 792.7+/-0.1 million sperm cells, and daily sperm production per gram of testicular parenchyma was 1.5+/-0.5, 3.2+/-0.6 and 6.4+/-0.6 million sperm cells for bulls at Stage 1, 2 and 3, respectively. Sire and amount of undegradable intake protein had significant (P<0.05) affects on the distribution of epididymal sperm reserves, with soybean meal-fed bulls having the higher proportions of epididymal sperm reserves in the cauda epididymis.