Influence of pre-slaughter holding time, growth path and castration on meat quality characteristics of beef M. Longissimus Thoracis : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Animal Science at Massey University

Abstract

The New Zealand Beef Industry has included among its research goals the need to enhance product consistency and consumer satisfaction. Identifying on-farm and post-slaughter techniques for producing quality meat will permit the delivery of a more consistent product. The objectives of this study were to examine the influence of castration, pre-slaughter holding time, and growth path on meat quality characteristics with emphasis on meat tenderness. Sixty male Hereford x Angus cattle were used, half of which were castrated at weaning. They were then ranked within their castration groups on their growth performance during a 100-day pretrial period. Of the 40 faster-growing animals, 20 were randomly selected to be slaughtered at 16-18 months of age at approximately 550 kg liveweight (the fast group; F) and the remaining 20 were managed in such a way that they reached the same liveweight as the slower-growing 20 animals (S) at 25 months of age (restricted group; R). Once at the abattoir half the animals were randomly selected within castration and growth path groups to be held for either 4 or 28 hours pre-slaughter. Measures of meat quality characteristics were made on a sample of the M. longissimus thoracis, of each animal that was removed soon after slaughter. The bulls produced meat with higher ultimate pH values (5.64 vs 5.46, P<0.001) and meat that was significantly tougher than steers as evaluated by MIRINZ peak force (6.6 vs 4.6 kg, P<0.001), and sensory toughness (6.10 vs 4.50, P<0.001), both before and after adjustment for differences in pH. Animals held for 4h pre-slaughter had tougher meat as measured by Instron compression maximum load (92.8 vs 82.0, P<0.05). Cattle in Group F produced meat that had a higher ultimate pH (P<0.001), however, meat from animals in Group F was significantly more tender as measured by sensory analysis (P<0.001). There were few differences between cattle in Groups R and S suggesting that differences in tenderness in this and other studies between animals on fast and slow growth rates were a result of differences in animal age rather than in inherent growth potential of the animals. Results suggest that holding cattle under appropriate welfare standards and allowing them enough time to recover from trucking and environmental stress should result in acceptable meat. Results from this trial have practical implications for producers and processors, and for the production of beef for the New Zealand Quality Mark. In this trial beef was tougher when it was from bulls or from older groups of cattle, with these two effects appearing to be additive. It is therefore suggested that cattle age and gender criteria should be considered for inclusion in the Quality Mark system.