Reproductive effects of feeding gossypol and vitamin E to bulls

An experiment was conducted to determine the effects of long-term feeding o f cottonseed meal on the reproductive traits of Holstein bulls. Holstein bu lls approximately 6 mo of age were placed on the following treatments: 1) s oybean meal + corn (CON); 2) cottonseed meal + corn (GOS); and 3) cottonsee d meal + 4,000 IU vitamin E.bull(-1).d(-1) (G+4E). The GOS and G+4E diets w ere formulated to supply 14 mg of free gossypol.kg(-1) BW.d(-1). These bull s had been in a previous experiment that evaluated the effects of feeding t he same type of diets, but from 2 wk to 6 mo, of age. Percentage of motilit y, percentage of normal and live sperm, and daily sperm production were les s (P <.05) in the GOS than in the other two treatments. Percentages of prim ary abnormalities and abnormal midpieces were greater (P <.05) in the GOS g roup 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 exhibit ed less sexual activity(P <.05) at the first test than bulls in other treat ments. Vitamin E supplementation in bulls that received gossypol improved t he 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 imp rove libido score. The results of the GOS first libido test may indicate la ck 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 bul ls had reached puberty on the basis of experimental protocol. Longterm feed ing of gossypol to Holstein bulls negatively affected some reproductive tra its; however, vitamin E supplementation countered these adverse effects and even improved these traits.