The Effects of Feeding Direct Solvent-Extracted Cottonseed Meal to Yearling Holstein Bulls on Growth Rate, Semen Quality, and Spermatogenesis.

A sensitive, rapid, and accurate method for extraction and analysis of gossypol in bovine plasma and tissue by high-performance liquid chromatography was developed. A three day old Guernsey bull calf absorbed gossypol after single oral dose of gossypol acetic acid in corn oil (5 mg/kg of body weight). Maximum level of plasma gossypol (5.5 ug/ml) was absorbed at 6 hours after treatment. Average gossypol recoveries from plasma and tissue samples spiked before extraction were 88.2% and 82.9%, respectively. Nine yearling Holstein bulls were used to evaluate the effect of feeding direct solvent-extracted cottonseed meal containing gossypol and soybean meal rations on growth rate, semen quality and spermatogenesis. Bulls on cottonseed meal were fed enough concentrate to provide an average daily gossypol intake of 6 and 30 mg per kg of body weight in Trials 1 and 2. Cottonseed meal concentrate fed in Trials 1 and 2 contained 3033.66 (+OR-) 0.25 mg of gossypol per kg of dry matter. Results of Trials 1 and 2 indicated that feeding direct solvent-extracted cottonseed meal containing gossypol to yearling Holstein bulls did not have a detrimental effect on growth rate, semen quality and spermatogenesis. Body weight, body length, wither height, and scrotal circumference was not affected by ration in Trials 1 and 2. Slope of heart girth of cottonseed meal bulls differed from soybean meal bulls. Bulls on cottonseed meal had a significantly higher increase in sperm volume per week than soybean meal bulls in Trial 1. Despite the daily intake of gossypol (30 (+OR-) 0.27 mg/kg of body weight), acrosomal integrity at 3 h and motility at 0 h were higher in semen of cottonseed meal bulls during Trial 2. Mean number of leptotene primary spermatocytes, Sertoli cells, and leptotene primary spermatocytes to Sertoli cells ratio of cottonseed meal bulls were not significantly different from soybean meal bulls. Spermatogonial mitosis was not affected by feeding cottonseed meal containing gossypol to yearling Holstein bulls. Gossypol was not found in tissue (liver, spleen, lung, heart, testis, kidney, and diaphragm muscle) or plasma samples. Steady-state of plasma gossypol was not observed. Gossypol was apparently degraded or inactivated in the rumen and was not absorbed at detectable levels