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Heritability of Rate of Gain in Young Growing Beef Cattle¹

Texas Agricultural Experiment Station²

Abstract

Data collected from four annual beef cattle gain-evaluation tests were analyzed. These data were from 853 head consisting of two breeds, one cross and three sex classifications. Cooperating breeders entered 266 of the calves and the station 587. Within the limits included in these data, initial age and weight have no important influence on subsequent gain on test. Determination of heritability from half-sib correlations using actual gain gave high estimates that are not considered valid because "sire x year" interaction could not be satisfactorily removed. Analyses using gain ratio, a relative measure obtained by dividing an individual's gain by the average of his sex, breed, year and ration group, gave estimates ranging from 33 to 51 percent for different classifications of breed or cross and pretest history. Estimates computed from data from station raised cattle only were smaller than from all cattle in all but one classification. This indicates that pretest ranch differences of cooperator cattle which were confounded with sire differences may bias heritability estimates upward. The most reliable estimate is considered to be that obtained by the method of regression of parent on average offspring using gain ratio. Calculated from 73 pairs including 291 offspring, it was 54 percent. These high heritability estimates add overwhelming support to the conclusion that selection for rate of gain will be effective when the individual's own record is used.

¹ In cooperation with U. S. Department of Agriculture; and is a part of the S-10, Southern Regional Beef Cattle Breeding Project. M. W. Hazen, Animal Husbandman, U.S.D.A., formerly stationed at Bluebonnet Farm, now Supt. Chinsegut Hill Sanctuary, Brooksville, Florida assisted in this work from 1949 to 1952.

² Bluebonnet Farm, McGregor, Tex.