Total Digestible Nutrients and Protein Levels for Dairy Bulls Used in Artificial Breeding

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Abstract
Using 18 bulls, 9 Holstein-Friesians, and 9 Guernseys, studies were conducted relating measurable semen characteristics, relative fertility, and body wt. changes to T.D.N. intake levels of approx. 100, 120, and 140% of recommended maintenance requirements for dry dairy cows of equivalent wts. fed simultaneously with concentrate mixtures containing 12, 16, and 20% total protein. These relatively wide ranges of T.D.N. intake, accompanied by considerable shifts in body wt., can be fed mature bulls for at least 90 days without influencing semen production or fertility. Under the conditions of this expt., 12% of protein in the concentrate mixture fed with mixed hay, containing approx. 10% of legumes, supplied enough protein for semen production and the maintenance of fertility. A tentative feeding standard for mature dairy bulls used routinely in artificial insemination is proposed. In terms of a practical feeding schedule, such a standard reduces itself to approx. 1 lb. of hay and 0.4 to 0.5 lb. concentrate mixture daily per 100 lb. of body wt.