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Productivity of Different Cow Genotypes: Culling Rates and Early Calf Performance¹

University of Wyoming, Laramie 82071

Abstract

Records of Jersey-sired (Jx), Santa Gertrudis-sired (Sx), Charolais-sired (Cx) and straightbred Hereford (H) cows were examined to determine culling rates, birth dates, weaning weights and average daily gains of their first, second and third calves. Culling categories were defined on the basis of number of calves weaned before removal from the herd. Calf performance data were analyzed by cow breed group and cow culling category. A second-degree polynomial model fit the data of all breeds, and accounted for a greater proportion of variation in percentage culled than did the linear model (P<.05). Total percentage culled through the study were 71, 67, 54 and 53 for the H, Sx, Cx and Jx cows, respectively. Culling rates in the H and Sx cows tended to be higher at earlier ages than in the Cx and Jx cows. Cow-culling category was a significant source of variation only on birth date of first calves. Cows culled after one calf had calves that were born later than cows in the other two categories (P<.05). Birth date, weaning weight and average daily gain of first calves varied with cow breed in that Jx cows had calves that were born earlier, gained faster and weaned heavier than first calves from the other breed groups (P<.05). First calves from Sx and Cx cows gained faster (P<.05) than calves from H cows. Analysis of calf traits for the second calves indicated that calves from the Jx cows were born earlier, gained faster and had heavier weaning weights than calves of the other breed groups (P<.05). Calves from Cx cows were born earlier (P<.05) than calves from H and Sx cows. There were no differences in calf traits of the third calves by cow breed group or culling category (P>.05).

¹ Published with the approval of the Director, Wyoming Agr. Exp. Sta. JA Number 1337.