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The Heritability of Some Economic Characteristics of Beef Cattle^{1, 2,}

Abstract

The present study is a summary of the data collected during ten years (1942–1951) of Record of Performance testing at the U. S. Range Livestock Experiment Station at Miles City, Montana. The data consist of records of 635 steers from grade cows mated to 88 sires from nine-lines. The characteristics studied were: birth weight, weaning weight, final weight at the completion of the feedlot period, gain in the feedlot, efficiency of feed utilization, shrinkage in shipment, slaughter grade, dressing percentage, carcass grade, color of eye muscle, area of eye muscle, and thickness of fat.

Intra-year and -line heritabilities were computed by the method of paternal half-sib correlation. The effects of differences between years, between lines within years, and between sires within lines were separated by the analysis of variance, and their relative magnitude was estimated, while the effects of age at weaning, and age and final weight at the completion of the feedlot period were removed by covariance.

The following results were obtained:

1. The effects of differences
   
   1. between years were highly significant for all characteristics.
      
   2. between lines within years were significant for efficiency of feed utilization.
      
   3. between sires within lines were not significant for carcass grade, were significant for weaning weight, and were highly significant for the other characteristics.
      
   4. The following estimates of heritability were obtained: birth weight 72, weaning weight 23, gain in the feedlot 60, final weight at end of feedlot period 84, efficiency of feed utilization 22, slaughter grade 42, shrink 91, dressing percentage 73, carcass grade 16, color of eye muscle 31, area of eye muscle 72, and thickness of fat 38.
      
   5. Selection for most growth characteristics should be based on the individual's own record, while selection for carcass characteristics must be based on sib or progeny test.
      
   
   

¹ Journal Series No. 341, Montana Agricultural Experiment Station, Bozeman, Montana.

² This study was conducted in cooperation with the Western Regional Project W-1, The Improvement of Beef Cattle Through the Application of Breeding Methods.

³ Agricultural Research Service, U. S. Department of Agriculture, U. S. Range Livestock Experiment Station, Miles City, Montana.

⁴ The authors wish to acknowledge the assistance of the following individuals during the course of the experiment: A. L. Baker, O. G. Hankins, Bradford Knapp, Jr. and J. R. Quesenberry of the Agricultural Research Service and F. S. Willson of the Montana Agricultural Experiment Station.