Effect of temperament and growth rate on tenderness of beef steaks from Simmental cross steers
Kohlbeck, Katelyn Storey.
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Tenderness has been identified as one of the most important traits consumers think about when choosing a steak. Unfortunately, the variation and lack of tenderness in steaks has created a negative eating experience for consumers. Recent research has raised the question if temperament as measured by exit velocity and docility scores could be a factor influencing variation in tenderness. However, docility scores are applied subjectively and exit velocity measurements require timers that can be expensive. An objective score that could be used would be helpful. Animals under stress often revert to anaerobic metabolism, especially in the muscle. Anaerobic metabolism results in elevated blood lactate suggesting the use of the small blood lactate meters as objective measures in identifying an animal's response to stress. The objective of this study is to determine if temperament effects growth rate and overall tenderness of beef steaks, and can blood lactate be used as an objective measurement of temperament. One hundred and fifty four steers were evaluated for exit velocity, blood lactate and docility score. Steers were humanely harvested and carcass data obtained. Loins from 30 steers were obtained and cut into steaks. The steaks were aged 3,7,14, and 21 days postmortem and used for shear force, and myofibrillar fragmentation index analysis. All temperament measurements were significantly correlated meaning if average lactate measurement went up the exit speed was high along with the docility score being higher. Temperament and growth classification significantly affected carcass weight. The animals that left the chute more slowly had lower carcass weights than did the steers that left the chute at a fast or medium rate. Additionally, blood lactate significantly affected shear values. Shear was significantly correlated to growth rate, along with blood lactate level. In conclusion temperament did not affect growth rate but did have an impact on tenderness. Our results suggest that growth rate, exit velocity and blood lactate contribute to variation in tenderness. Finally, if an animal is temperamental based on exit scores and lactate concentrations before harvest this could set the stage for postmortem processes that contribute to the high variance in tenderness in the marketplace.