The effect of dam genotype on carcasses of weaner progeny.

Abstract

Animal Production in Australia Vol. 15 THE EFFECT OF DAM GENOTYPE ON CARCASSES OF WEANER PROGENY J.H.L. MORGAN*, A.J. CLARK* and G.R. SAUL* Using crossbred cows derived from suitable breeds is a way of increasing weaning weights and weaning rates (Baker et al. 1981; Deland 1982). However, more information is needed on the carcass characteristics of the progeny of crossbred cows. In 1978 cows derived from Hereford (H), Friesian (F), Charolais (C) and Brahman (B) sires and H and F dams were mated to H bulls (Morgan and Clark 1982). All the resulting progeny, except females from HH, FF and CF dams were slaughtered at 9 months of age. Measurements taken on 140 carcasses were analysed by least squares with means adjusted for dam age, sex and slaughter age. Results for the effects of breed of grand-sire (GS) and breed of grand-dam (GD) are presented in Table 1. TABLE 1 Effect of dam genotype on carcasses of weaner progeny Breed of GS and breed of GD significantly affected most traits. The GS x GD interaction was not significant for any trait probably because of low numbers. Where numbers were larger this interaction did have a significant effect on weaning weight (Morgan and Clark 1982). The ranking of dam genotypes according to the carcass weight of their weaners was very similar to their ranking for calf weaning weight when mated to Simmental sires in previous years. However, there was a tendency for the weaners of dams with a H component to rank relatively poorly when sired by H bulls; this can be explained by a decrease in the heterozygosity of the calves with a reduction in the growth benefit from hybrid vigour. Carcasses of weaners from dams with F sires were the heaviest, longest, had the highest dressing percentage, the largest eye muscle area (except for C sired dams) and the greatest fat depth. Weaners from C sired dams had heavier, longer carcasses with larger eye muscle areas than the progeny of H and B sired dams. Weaners with F grand-dams had heavier carcasses with a higher dressing percentage and a larger eye muscle area than weaners with H grand-dams. These results show clearly that calves from straightbred Friesian cows and from crossbred cows mated to Hereford bulls yield heavier carcasses which are not leaner than those from straightbred Hereford cows. Research conducted in south-eastern Australia and in New Zealand has that dairy-beef cross cows have a very high performance per cow in almost aspects of beef productivity. Adoption by the industry, however, is very mainly due to prejudice, a reluctance to purchase replacements, especially calves from dairy herds, and an inadequate transfer of knowledge. fi:254. shown all low as BAKER, R.L., CARTER, A.H. and MULLER, J.P. (1982). Proc. N.Z. Soc. Anim. Prod. DELAND, M.P.B. (1982). Proc. Wld. Cong. Sheep and Beef Cattle Breed. 2:219. MORGAN, J.H.L. and CLARK, A.J. (1982). Proc. Aust. Soc. Anim. Prod. G:619. * Pastoral Research Institute, P.O. Box 180, Hamilton, Vic. 3300 Australia. 723