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U. S. Department of Agriculture, University of Nebraska and Michigan State University
Abstract
The experiment involved records on 375 steer and 362 heifer calves born over a four-year period, 1960 to 1963 inclusive, at the Fort Robinson Beef Cattle Research Station in northwestern Nebraska. The calves were from 80 cows each from the Angus, Hereford and Shorthorn breeds, and were the progeny of 17 Angus, 16 Hereford and 16 Shorthorn sires. Traits studied were birth weight, weaning score, and adjusted 200-day weight (steers and heifers); adjusted final weight, marbling score, final carcass grade, fat thickness, rib-eye area and actual cutability (steers); and adjusted 550-day weight (heifers).
There were no differences in the sire components of variance between the straightbreds and crossbreds, indicating similar additive genetic variance in the two groups. Estimates of components of variance for between and within sires were obtained separately for each breed of sire and breed of dam group. These components were pooled to give heritability estimates in straightbred and crossbred populations. The pooled analyses yielded estimates of heritability from 0.15 to 0.85 with most standard errors between 0.3 and 0.4. No difference was noted between the estimates from crossbreds and straightbreds. Estimates of genetic and phenotypic correlations for the pooled within straightbred analyses are presented. High estimates of genotypic and phenotypic correlations were noted among the traits associated with weight (birth and 200-day weight, final weight, 550-day weight, rib-eye area, and actual cutability). Standard errors, in general, varied from 0.3 to 0.4. Estimates of the correlation between a sire's genetic ability to produce straightbred and crossbred progeny were high indicating that mass selection in purebred populations contributing germ plasm to crossbred populations would be approximately as effective in improving commerical crossbred performance as it would be in improving commercial straightbred performance.
1 Michigan Agricultural Experiment Station Journal Article No. 4853. This manuscript resulted from cooperative research between the U.S. Department of Agriculture, University of Nebraska and Michigan State University. This study is a contribution from the North Central Regional Project NC-1, Improvement of Beef Cattle Through Breeding Methods.
2 Department of Animal Husbandry, Michigan State University, East Lansing. The data reported herein are a portion of a thesis submitted to the School of Advanced Graduate studies, Michigan State University, by the senior author in partial fulfillment of the requirements for the Ph.D. degree. The authors would like to express appreciation to Walter R. Harvey, Ohio State University, for assistance in the statistical analysis of the data in this manuscript.
3 U. S. Meat Animal Research Center, Animal Husbandry Research Division, A.R.S., U.S.D.A., Clay Center, Nebraska.
4 Beef Cattle Research Branch, Animal Husbandry Research Division, A.R.S., U.S.D.A., Lincoln, Nebraska.
5 Department of Animal Science, University of Nebraska, Lincoln.
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  A. Rios-Utrera, L. V. Cundiff, K. E. Gregory, R. M. Koch, M. E. Dikeman, M. Koohmaraie, and L. D. Van Vleck Genetic analysis of carcass traits of steers adjusted to age, weight, or fat thickness slaughter endpoints J Anim Sci, April 1, 2005; 83(4): 764 - 776. [Abstract] [Full Text] [PDF]
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