Genetic parameters for liveweight, wool and worm resistance traits in multi-breed Australian meat sheep: 2. Genetic relationships between traits

Abstract

Australian sheep breeders aim to simultaneously breed sheep that have high growth rate, superior carcass quality and are resistant to internal parasites. The objective of this study was to estimate genetic and phenotypic relationships between 11 traits recorded in Australian meat sheep, covering liveweight, carcass and internal parasite resistance traits. The data comprised 1 046 298 animals from 149 Poll Dorset, 17 Suffolk, 24 Texel and 118 White Suffolk flocks. Within all trait groups, the different age expressions were moderately to highly correlated. The genetic correlations between liveweight with both fat and eye muscle depth were generally negative ranging between -0.10 and -0.42. Fat and eye muscle depth were moderately correlated (0.27-0.59). Results indicate that selection for an increase in liveweight will have a negative effect on fat and eye muscle depth. The negative correlations of ultrasound scan traits and worm egg count indicates that animals with high genetic merit for fat and eye muscle depth are less prone to infection from internal parasites. The results from this study have been used to review the genetic correlations used in the LAMBPLAN routine genetic evaluations conducted by Sheep Genetics.