This study was conducted to evaluate the susceptibility of the Dorper and Merino breeds to pre-slaughter conditions stress at a commercial abattoir and how it affects the quality of the meat produced. The objective of this study was to investigate differences in post-mortem energy metabolites, glycolytic potential and meat quality attributes from Muscularis longimissius thoracis et lumborum (LTL) between Dorper and Merino lambs slaughtered at a commercial abattoir. Meat samples (~50 grams of LTL) harvested from 100 female eight-month old of the Dorper (n=50) and Merino (n=50) lambs were used in this study. For measuring post-mortem energy metabolites (glycogen, lactate, glucose-6-phosphate and glucose content) sampling was done on each carcass ~ 30 minutes post-slaughter and the samples were immediately frozen (-196 °C) in liquid nitrogen to prevent further glycolysis. The pH and temperature were measured 45 minutes, 6 and 24 hours post-slaughter, and carcass measurements were taken. Colour coordinates (lightness (L*), redness (a*), yellowness (b*)) were measured at 24 hours after slaughter and hue angle (H*) and chroma (C*) were calculated. Furthermore, thawing loss (TL), cooking loss (CL) and Warner Braztler Shear Force (WBSF) were measured after 7 days post-slaughter storage (-20 ºC). The Dorper had lower glycogen levels thus produced meat with a high ultimate pH and tougher meat compared to the Merino breed. The relationships observed between post-mortem muscle metabolites, glycolytic potential and meat quality attributes indicate that meat quality is affected by glycogen levels at slaughter. The results indicate that the Dorper breed was more susceptible to pre-slaughter stress and thus produced meat with reduced quality compared to the Merino breed.
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