Simple Versus Complex Concentrate Mixtures for Young Breeding Bulls. I. Growth, Blood Composition, and Cost

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Abstract
A study was made of the growth, blood picture and cost of maintenance of bulls fed 2 greatly different concentrate mixtures during the interim 18 to 33 mos. of age. At 18 mos. of age 2 groups of 6 bulls were selected on the basis of uniformity of size, blood and semen composition from 16 bulls which had been managed under the same conditions since birth. Group I received a simple concentrate mixture of which corn and corn gluten meal consti- [center dot] tuted 64%, while Group II was fed a complex concentrate feed containing supplementary vitamins and minerals. The complex concentrate mixture used in this study provided 2.91 g. more Ca, 1.63 g. more P, 40 mg. more''Fe, 86 mg. more Mn, 6 mg. more Cu, 0.45 mg. more Co, 44.31 g. more protein, 8.85 g. more fat, 13,620 I. U. more vitamin A and 2,043 U.S.P. units more vitamin D per lb. than was supplied in the same amt. of simple concentrate feed. The bulls of both groups received the same hay at the rate of 1 lb. per 100 lb. body wt. daily with concentrate feed in sufficient quantity to provide an avg. daily digestible nutrient intake of approx. 1.02 and 1.18 lb. per 100 lb. body wt. before and after an avg. age of 760 days, respectively. Good growth at equivalent rates was effected by both feeding regimes. The characteristics and constituents of the blood studied were similar for both groups and are suggested as "normals" for bulls of simitar ages. The hematocrit, mean corpuscular hemoglobin and vol., the level of hemoglobin, reduced and total G-SH, and plasma Ca increased with aging; the plasma concn. of inorganic P decreased. Maintenance of bulls on the complex concentrate feed cost approx. 50% more than that of bulls receiving the simple concentrate mixture.