RESUMO
An experiment was conducted to determine the effects of long-term feeding of cottonseed meal on the reproductive traits of Holstein bulls. Holstein bulls approximately 6 mo of age were placed on the following treatments: 1) soybean meal + corn (CON); 2) cottonseed meal + corn (GOS); and 3) cottonseed meal + 4,000 IU vitamin E x bull(-1) x d(-1) (G+4E). The GOS and G+4E diets were formulated to supply 14 mg of free gossypol x kg(-1) BW x d(-1). These bulls had been in a previous experiment that evaluated the effects of feeding the same type of diets, but from 2 wk to 6 mo. of age. Percentage of motility, percentage of normal and live sperm, and daily sperm production were less (P<.05) in the GOS than in the other two treatments. Percentages of primary abnormalities and abnormal midpieces were greater (P<.05) in the GOS group than in the other two groups. At 12 and 16 mo. of age, bulls were given two assessments for sex drive traits. Bulls that received gossypol exhibited less sexual activity (P<.05) at the first test than bulls in other treatments. Vitamin E supplementation in bulls that received gossypol improved the number of mounts in the first test and the time to first service in the second test. There was a trend of gossypol to decrease and vitamin E to improve libido score. The results of the GOS first libido test may indicate lack of sexual maturity, which agrees with sperm production data. At the time of first test (12 mo. of age), none of GOS, two of CON, and six of G+4E bulls had reached puberty on the basis of experimental protocol. Long-term feeding of gossypol to Holstein bulls negatively affected some reproductive traits; however, vitamin E supplementation countered these adverse effects and even improved these traits.