Estimates of Genetic Parameters for Seasonal Weight Changes of Beef Cows

Genetic parameters were estimated for seasonal body weight changes of cows and weaning weight of their calves in two beef herds run at pasture in a Mediterranean climate. Heritability estimates for weight changes were low. Cows predisposed to lose more weight were also likely to gain more weight, and larger cows had greater genetic potential for weight changes. Low to moderate genetic and permanent environmental correlations indicated that cows with greater seasonal weight changes weaned heavier calves, due in part to the genetic association between weaning weight and cows' mature body weight. Results indicate that in this environment, scope to select for heavy weaning weight without penalty to cow body weight during periods of seasonal feed scarcity is limited.