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

Abstract

Summary Using 18 bulls, 11 Holstein-Friesians, 6 Guernseys and 1 Ayrshire, studies were conducted relating 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. The results, as judged, by the averages for volume of semen per ejaculate, per cent of motile spermatozoa and their rates of motility, the number of spermatozoa per mm. 3 of semen, the methylene blue reduction time and the per cent of usable samples during a 120-day period, showed that corn gluten feed, skim milk powder and soybean oil meal were approximately equal in value as protein supplements in the concentrate mixture. Based on 60 to 90 days non-returns to first service cows, the average fertility levels of the semen produced when the bulls were fed corn gluten feed, skim milk powder and soybean oil meal were 63.5, 61.6 and 65.7 per cent, respectively. While the average per cent non-returns 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 relatively small and it is doubtful whether any real advantage lies with the soybean oil meal. In these studies, animal protein was not superior to the plant proteins. The monetary economy of the particular plant protein sources used in these trials was much greater than for the animal protein source. A T. D. N. intake of 110 per cent of Morrison's recommended requirements for the maintenance of dry dairy cows of equivalent weight resulted in consistent body weight increases for all bulls during the first 240 days but consistent decreases during the last 120 days of the experiment. While the decreases occurred during the summer and early fall months, it was not definitely established whether the observed decreases represented a true cause and effect relationship.