Semen Production and Fertility of Dairy Bulls Fed Rations Containing Proteins of Plant and Animal Origin

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Abstract
18 mature breeding bulls were used in studies conducted to relate differences in measurable semen characteristics and relative fertility to concentrate mixtures containing corn gluten feed, skim milk powder or soybean oil meal as the protein supplement when fed with timothy hay as the only roughage. As judged by semen vol. per ejaculate, % of motile spermatozoa and their rates of motility, the no. of spermatozoa per cu. mm. of semen, the methylene blue reduction time and the % of usable samples during 120-day feeding periods, the 3 protein supplements were approx. equal in value. On the basis of 60- to 90-day non-returns to 1st service cows the % non-returns for the corn gluten feed, skim milk powder, and soybean oil meal were 63.5, 61.6 and 65.7, respectively. While the fertility level was significantly higher during the periods when soybean oil meal was fed as compared to the periods when skim milk powder was fed, the difference was small and it is doubtful whether any real advantages lie with the soybean oil meal. In these studies animal protein was not superior to plant protein.