AN EVALUATION OF SEVERAL MEASUREMENTS OF BEEF COW SIZE AS RELATED TO PROGENY PERFORMANCE

Abstract

A study with 173 cows from the University of Alberta beef breeding herd (1969–1970 data) was conducted to investigate the interrelation of cow body-size variables and the effect of selected cow-size variables on calf performance. The cows were classified into two breed categories: Hereford and Angus–Galloway crosses (HEAG) and hybrid and other breed crosses (HYC). Measurements of cow body-size included: postcalving weight (PCW), weight when calves were weaned (WCW), height at withers (HW), height at sacrum (HS), and average wither-sacral height (H), body length (L), and heart girth (G). Heart girth was more highly correlated with body weight than either length or height measurements, indicating that G reflects condition of animal, whereas L and H measurements tend to reflect skeletal size. Body weight was highly correlated with both PCW/H and WCW/H ratios. Weight–height ratios appeared to reflect condition; WCW/H was considerably higher than PCW/H (4.13 vs. 3.32 for HEAG and 4.02 vs. 3.15 for HYC). Across breed and age of dam a 10-kg increase in PCW resulted in a 0.7-kg increase in weaning weight of calf. A 1-cm increase in H resulted in a 0.97-kg increase in weaning weight of calf. Within breeds, preweaning performance of calves was more closely associated with H than with PCW in HEAG dams and about equal to H and PCW in HYC dams. Postweaning average daily gain was positively associated with both PCW and H for HYC dams but negatively associated with PCW for HEAG dams. For HEAG dams a 10-kg increase in PCW resulted in a 0.47-kg decrease in final weight of male calves and a 1-cm increase in H resulted in a 3.7-kg increase. For HYC cows, a 10-kg increase in PCW resulted in a 1.91-kg increase in final weight of male calves and a 1-cm increase in H resulted in a 0.82-kg increase in final weight of male calves.