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Genetic Variation among and within Herds of Angus and Hereford Cattle^{1, 2,}

U.S. Department of Agriculture, Clay Center, Nebraska 68933

Abstract

Birth and livability data on 995 calves born, weaning data on 915 calves and carcass data on 817 calves produced in two calf crops were studied. Calves were sired by 51 bulls from 18 Angus herds and 44 bulls from 18 Polled Hereford herds (two to four sires sampled/herd) through AI matings to Hereford and Angus cows at the U.S. MARC.

Estimates of genetic variance did not differ significantly between breeds. From pooled analyses, effects of herd origin of sires were significant for birth weight, 200-day weight, postweaning average daily gain, 452-day weight, marbling, final carcass grade and carcass conformation grade. Effects of sire/herd were highly significant for postweaning average daily gain, 452-day weight, carcass conformation, final grade, marbling, fat thickness, longissimus muscle area and significant for estimated cutability.

Genetic variance components for herds and sires/herd were used to compute the intraherd correlation of individual breeding values. Relatively higher correlations for growth traits (averaging .51) than for carcass traits (averaging .16) indicate that selection pressures and responses have been more diverse, among herds, for growth traits than for carcass traits.

¹ The cooperation of the Nebraska Agricultural Experiment Station is acknowledged.

² Cooperation of the American Angus Association and the American Polled Hereford Association and the efforts of Stanley P. Anderson and Mack Patton formerly associated with the respective associations for their assistance is gratefully acknowledged. The authors gratefully acknowledge G. E. Dickerson for suggestions on theoretical aspects of the study.

³ U.S. Meat Animal Research Center, North Central Region, Agricultural Research Service.

⁴ Present Address: Department of Animal Science, Texas A&M University, College Station.

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