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Heritability of Weaning Grade in Range Beef Cattle

University of California, Davis^,2

Abstract

The heritability of weaning grade has been estimated in two experimental range herds, A and B, of similar breeding that were managed alike except that in Herd A cows were supplemented during the fall and winter when the range was nutritively deficient while the cows in Herd B were not supplemented. On the basis of paternal half sib relationships heritability estimates were made within each of three generations for each herd. The estimates for Herd A were consistently higher than those for Herd B. However, the herd difference in the estimates was not statistically significant. The average value of the heritability estimated for the two herds was 36%.

On the basis of selection experiments extending over two generations heritability of weaning grade in Herd A was estimated to be 42% and in Herd B 29%.

Within years there was a correlation of .42 between weaning grade and weaning weight. The square of this correlation is .18, thus 18% of the variance in weaning grades within years was due to variation in weaning weight. Sex, herd and pasture differences in weaning grade were adequately explained on the basis of this correlation.

¹ San Joaquin Experimental Range, O'Neals, California.

² In co-operation with the U.S.D.A. under Western Regional Project W-1 on beef cattle breeding research.