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Blood Composition of Hereford Steers. II. Effects of Ranch and Sire¹

South Dakota State University, Brookings

Abstract

Eighty-four steers from 15 sires and six ranches and 74 steers from eight sires and four ranches were used in time- and weight-constant trials, respectively, to determine the relative effects of additive genetic (sire) and permanent environmental deviations (ranch) on certain blood components. Blood specimens were collected at an average initial age of 223 days and at slaughter. The weight-constant animals were slaughtered at 363, 408, 454 or 499 kg. All animals were maintained in the same lot during the same year on an ad libitum high-energy ration. Each ranch cell contained at least one bull produced and leased by the South Dakota Agricultural Experiment Station to the cooperating private producer. All initial and final ages and weights were significantly affected by ranch differences. Sire differences were also highly important for several age and weight traits. Therefore all blood traits were adjusted by regression for the linear and quadratic effects of age and weight. The only significant sire differences were observed for M.C.V. and M.C.H. in the final time-constant data, although heritability estimates greater than 0.30 were derived for acid phosphatase, inorganic phosphorus, amino acid nitrogen, icteric index and number of basophils in the combined initial data. Generally, ranch differences were much more important than sire differences, indicating that permanent environmental deviations have a larger effect on most items of blood composition than additive genetic differences. For several blood traits, ranch effects were significant in initial analyses but not final analyses whereas other blood traits exhibited a converse pattern. The only significant sire x weight class interaction was for plasma amino acid nitrogen.

¹ Department of Animal Science, published with the approval of the South Dakota Agricultural Experiment Station as Publication 784 of the Journal Series. Cooperative with A.R.S., U.S.D.A and a contribution from Regional Project NC-1, Improvement of Beef Cattle through Breeding Methods.

² Present address: Department of Animal Science, The Pennsylvania State University, University Park.

³ The authors wish to express their appreciation to R. J. Emerick, Department of Biochemistry, W. L. Tucker, Station Statistician, and Mrs. Elizabeth Christianson, Department of Animal Science, for assistance in conducting this study.