Breeding Behavior, Spermatogenesis, and Semen Production of Mature Dairy Bulls Fed Rations Low in Carotene

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Abstract
Six dairy bulls were fed dry roughages low in carotene (0.56-4.24 mg. per lb.) and a concentrate mixture deficient in carotene and vitamin A for a period of 16 months without inducing clinical manifestations of vitamin A deficiency or noticeable impairment of semen production. Subsequent changes in the roughage component of the ration of 3 bulls to dried beet pulp and the same concentrate mixture but without added carotene resulted in the development of incoordination, edema of the extremities, papillary hemorrhage, a gradual increase in the per cent of abnormal spermatozoa, but no consistent change in the number of spermatozoa per ml. of semen within a period of 40-120 days. Although the bulls were unable to mount, they exhibited an unusual amt. of libido. Typical patterns of degeneration of the germinal epithelium were found in the bulls on the carotene-deficient rations. There were few spermatogonia, spermato-cytes, spermatids or maturing spermatozoa in the lumen of the tubules. While supplementing the carotene-deficient ration of the bulls prevented the degeneration of the germinal epithelium, it produced no consistent changes in semen production which reasonably could be attributed to the carotene. Plasma carotene and vitamin A values throughout the expt. and liver carotene and vitamin A concn. at its termination are reported. No data on fertility were obtained.