"Estimates of genetic parameters for mature weight of Australian beef cows and its relationship to early growth and skeletal measures"

K. Meyer

Livestock Production Science 44 : 125-137.

Abstract

Estimates of genetic parameters were obtained for mature weight and the two parameters of a Gompertz growth curve, namely average mature weight and rate of maturing, fitted for each animal for a herd of Polled Hereford cows and a herd of multi-breed synthetic cows, so called Wokalups. Both herds were part of a selection experiment for preweaning growth rate conducted in Western Australia. In addition, cannon bone length, measured at birth, and hip height, recorded at weaning, and their association with birth, weaning and final weights were examined.

Wokalups consistently exhibited more phenotypic and genetic variability than Herefords with higher heritabiliy estimates for all traits. Heritabilities for average mature weight were 0.47 for Herefords and 0.73 for Wokalups compared to values of 0.29 and 0.54, respectively, for mature weights treated as repeated records. Rate of maturing was moderately heritable in both breeds, heritability estimates being 0.32 and 0.33. Genetic correlations between cannon bone length and mature size were 0.6 to 0.7 and between cannon bone length and rate of maturing were -0.5 to -0.6. There was an adverse genetic correlation, -0.5 for Herefords and -0.7 for Wokalups, between rate of maturing and mature weight, i.e., earlier maturing animals tended to have shorter cannon bones and lower mature weights. Scope for a genetic evaluation for mature size, including cannon bone length as an indicator trait, is discussed.

Key words : Beef cattle, Mature Weight, Cannon Bone Length, Genetic Parameters, Growth

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