EFFECTS OF DIETARY GOSSYPOL ON ASPECTS OF SEMEN QUALITY, SPERM MORPHOLOGY AND SPERM PRODUCTION IN YOUNG BRAHMAN BULLS

Eight young reproductively normal Brahman bulls (average age and bodyw eight 20 months and 500 kg, respectively) received either cottonseed m eal delivering 8.2 g free gossypol/bull/d (treatment group, n=4) or so ybean meal (control group, n=4) for 12 wk. After adjustment (1 wk), we ekly procedures (11 wk) included blood collection, scrotal circumferen ce measurement acid electroejaculation. Semen assessments included spe rm motility, percentage of live spermatozoa, general sperm morphology (using brightfield microscopy), and midpiece morphology (using DIC mic roscopy). After sacrifice (Week 12), sperm production rates (daily and per gram testicular parenchyma) were determined. Treated bulls did no t differ from controls in scrotal circumference or the percentage of l ive spermatozoa. Sperm motility differed at Weeks 9 (P<0.05), 10 and 1 1 (both P=0.06). Treated bulls had fewer normal spermatozoa at Weeks 5 (P<0.05), 6 (P<0.01) and 7 thru 11 (P<0.001). Beginning from Week 3, treated bulls showed an increased proportion of sperm midpiece abnorma lities (P<0.05) which stabilized at 52 to 62.5% between Weeks 5 and 11 (P<0.01 or P<0.001). Treated bulls also had lower sperm production th an untreated bulls, both on a daily (P<0.01) and per gram testicular p arenchyma (P<0.001) basis. A cottonseed supplement providing 8.2 g of free gossypol per bull per day had adverse effects upon both sperm mor phology and spermatogenesis in young Brahman bulls, with the former be ing first evident within 3 to 4 weeks of feeding of cottonseed meal.