FACTORS INFLUENCING MILK YIELD OF BEEF CATTLE

The joint and separate effects of several cow-calf variables on milk yield were studied with 176 and 201 beef cows from the University of Alberta beef breeding herd for 1966 and 1967, respectively. The dams consisted of Hereford, Aberdeen Angus, Galloway and hybrid breeding. Independent variables considered were: breed, post-calving weight, winter weight loss, summer weight gain and age of dam, and weaning age, sex and birth weight of calf. Total variance of milk yield explained by all variables together was only 40 and 52% for 1966 and 1967, respectively. Breed and age differences of dam accounted for 82 and 87% of explained variance in milk yield respectively for 1966 and 1967. Holding cow age constant, post-calving weight of cow explained 0.0 and 8.5% additional variance in milk yield for 1966 and 1967, respectively. Summer weight gain of cow was negatively associated with milk yield. Winter weight loss of cow had little influence on milk yield. There appeared to be a negative relationship between earl...