Abstract

A collaborative beef cattle project between AgResearch and Adelaide University is described, which had the aim of identifying genetic markers (DNA markers) for carcass composition and meat quality traits. Two extreme breeds were used, the Jersey and Limousin, and first-cross Jersey x Limousin bulls were mated to cows of both breeds to produce experimental animals in two herds, in New Zealand and Australia. The present paper provides information on relationships among some traits recorded in the New Zealand herd, with a total of 416 back-cross cattle of both sexes slaughtered as 2-year-olds at Ruakura in the springs of 1998 and 1999. The recorded data included hot carcass weight and the butcher-dissected weights of meat, fat and bone in the right side, expressed as percentages of side weight (MP, FP and BP respectively). The pH decline in the right striploin, removed from the carcass after dressing and maintained at a constant 15°C, was monitored to derive the initial (pH1), ultimate (pHu), and the rate of fall of pH. Average shear force (SAVG) and the half-life of the ageing rate (SHLF) were measured in striploin steaks cooked immediately after rigor and then at intervals until ultimate tenderness. Percentage weight loss (PWL) during cooking was recorded. Also measured in the striploin were the concentrations of three metabolic enzymes, lactate dehydrogenase (LDH), isocitrate dehydrogenase (ICDH) and 3-hydroxyacyl-Coenzyme A dehydrogenase (HAD), and the proteolytic enzymes m- and milli-calpain, and their inhibitor calpastatin (CAST). Glycogen concentration in the muscle at slaughter, expressed as the glycolytic potential (GLYP), was estimated from the sum of the concentrations at rigor of glucose, glucose-6-phosphate, lactate and residual glycogen. The range of pHu values was small, probably because all animals were regularly handled. Correlations, after adjustment for breed group, sire and slaughter group, included: MP with FP, -0.82; PWL with MP, 0.20; PWL with FP, -0.29; MP with enzymes LDH, ICDH and HAD, 0.22, -0.21, -0.03; FP with ICDH, 0.16; SAVG with SHLF, 0.48; SHLF with CAST, m-and milli-calpain, 0.28, -0.14, 0.03; CAST with m- and milli-calpain, 0.26, 0.38; GLYP with pH1 and pHu -0.01 and -0.17. Overall, HCW, MW and composition traits were not correlated with pH traits or SAVG, or m- or milli-calpain concentrations; HCW and MW were positively correlated with LDH and GLYP.

CA, Morris, CC Daly, NG Cullen, and SM Hickey

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 96-99, 2001