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Repeatability of Calf Weight and Ratio of Calf Weight to Cow Weight in Hereford and Angus^{1 ,2,}

University of Arkansas³, Fayetteville 72701

Abstract

Data were collected from 586 Hereford calves produced by 236 cows and 909 Angus calves from 356 cows. Repeatability estimates were calculated for actual weaning weight, 205-day weight, 205-day weight adjusted for sex, 205-day weight adjusted for age of dam, and 205-day weight adjusted for sex and age of dam using Beef Improvement Federation (BIF) adjustment procedures. The repeatability estimates of the 205-day weight adjusted for sex and age of dam were .35 ± .05 and .25 ± .04 for Hereford and Angus, respectively. Repeatability of the ratio of these weights to cow weight at weaning was also calculated. Higher repeatability estimates were obtained for the ratios of calf weight to cow weight than for estimates calculated from adjusted calf weights. Estimates of .52 ± .04 and .43 ± .04 for the Hereford and Angus, respectively, were essentially the same as the estimate when adjustment was made for both sex and age of dam. In a subsequent least-squares analysis calf weight records were corrected for significant main effects and interactions using least-squares constants derived from the data. Repeatability estimates of adjusted 205-day weight were .34 ± .05 and .24 ± .04 for Hereford and Angus, respectively, while estimates of the adjusted ratio of 205-day weight to cow weight at weaning were .53 ± .04 and .40 ± .04 for Hereford and Angus, respectively. Estimates of repeatability from regression of later records on earlier records were generally similar to the above estimates.

¹ Published with the approval of the Director of the Arkansas Argricultural Experiment Station.

² A contribution to S-10 Regional Breeding Project.

³ Department of Animal Sciences.