Genetic parameters for liveweight and ultrasonic fat depth in Australian meat and dual-purpose sheep breeds

Abstract

The genetic and phenotypic variances and covariances for liveweight at 5 to 19 months of age and ultrasonic subcutaneous fat depth were estimated using REML procedures for the Border Leicester, Suffolk, Corriedale, Coopworth and Gromark breeds. The data comprised 12 923 progeny from 46 flocks, representing 590 sires, and were collected by the New South Wales Meatsheep Testing Service between 1981 and 1990. Fixed effects included in the model were management group, birth type, rearing type, age of dam and age of lamb. Each breed was analysed separately, and the larger breed data sets (Border Leicester and Suffolk) were split on age at measurement. The estimates of heritability for the various data sets ranged from 0.09 � 0.09 to 0.40 � 0- 10 for liveweight and 0.07 � 0.08 to 0.40 � 0 -07 for fat depth. There was a moderate positive genetic correlation (0 - 14 to 0.77) between liveweight and fat depth. Adjustment of fat depth for liveweight reduced this genetic correlation (-0.34 to 0.24) and had little effect on the heritability of fat depth, which then ranged from 0-06 � 0-08 to 0.44 � 0.07. Variation in estimates between the breeds is discussed. The results will be used to provide breed-specific parameters to improve the accuracy of Estimated Breeding Values produced by LAMBPLAN, Australia's national performance testing scheme for meatsheep. The mean age of sires at the birth of progeny varied from 3-2 to 3-5 years amongst the breeds, with 14% to 30% of animals sired by rams 5 years of age or older. Sire-use patterns in some breeds indicated high levels of inbreeding.

Genetic analysis of weight, fat and muscle depth in growing lambs using random regression models

“…Furthermore, McEwan et al (1993) presented genetic correlations in Romney sheep of 0·56, 0·45, 0·38 and 0·67 between BW and FD at ages of 5, 6, 8 and 14 months. Brash et al (1992) estimated a genetic correlation of 0·77 between weight and fat measures at an average age of 290 days in Border Leicester data, which is more in agreement with our results. Despite minor differences, the correlation pattern was similar for all three studies, in that correlations were moderate to high and positive, which is supported by our results.…”

“…Estimates from these two studies correspond well with estimates presented in this study (0·53, 0·48 and 0·51 at 150, 270 and 360 days of age). Also, Brash et al (1992) reported correlations of 0·52 and 0·51 in Border Leicester data at average ages of 290 and 420 days.…”

Genetic analysis of growth traits in Mecheri sheep

“…Mavrogenis et al (1990) The estimates in indigenous breeds ranged from 0.10 in Hissardale (Akthar et al, 2007) to 0.89 in Kashmir Merino (Sheikh et al, 1986) breeds while in exotic breeds, the direction varied from negative and low (Veseley et al, 1970;Dzakuma et al, 1978) to positive and high (Mani et al, 1982). Estimates of heritability for weaning weight by animal model ranged between low (0.06) to high (0.45) in dual purpose breeds (Boujenane and Kansari, 2002;Brash et al, 1994).…”

“…The estimates in exotic breeds of sheep ranged from medium and negative to low and positive (Kirmani et al, 1986). In Poll Dorset and Suffolk, the estimates of heritability for nine months weights by animal models were reported as 0.21 (Atkins et al, 1991) and 0.31 (Brash et al, 1992) respectively.…”

“…In exotic breeds the estimates ranged between 0.11 (Dzakuma et al, 1978) and 0.82 (Bassett et al, 1967) in Hampshire and Rambouillet breeds respectively. Atkins (1986) Animal model estimates of heritability for 12 months weight ranged from medium (0.13) to high (0.49) in dual purpose breeds (Brash et al, 1994;Wulji et al, 1998) and was medium (0.11 to 0.25) in meat breeds (Gilmour et al, 1994;Janssens et al, 2000).…”