The effects of distance, lairage duration and animal-related factors on pre-slaughter stress indicators, carcass characteristics, nanostructure and technological properties of beef

Abstract

The main objective of the current study was to determine the effect of distance travelled (DT), lairage duration (LDhr) and animal-related factors (animal class, breed, sex) on pre-slaughter stress indicators, carcass characteristics, nanostructure and technological properties of beef. The study was conducted in an Eastern Cape abattoir under the Buffalo City District Municipality. Six genotypes of cattle (Beefmaster, Bonsmara, Brahman, Holstein-Friesian, Non-descript and Nguni) brought for slaughter at the abattoir on different days were used in the study. Slaughter weight (SWT), warm and cold carcass weight (WCW and CCW), fatness and conformation of each animal were measured and recorded. Representative samples of blood plasma and meat quality from the Muscularis thoracis et lumborum (LTL) were collected at slaughter and 24 hours after slaughter, respectively. Heat shock proteins 70kDa (HSPA1A), glucose (GLU), cortisol (CORT), creatine kinase (CK) and lactate dehydrogenase (LDH) were determined from the blood plasma. The representative LTL muscle was used to determine ultimate pH (pHu), lightness (L*), redness (a*), yellowness (b*), meat temperature (Tm), Warner Bratzler Shear Force (WBSF) and histological structure of beef. There were significant effects of distance on pHu, Tm, a*, b*, TL%, CK and LDH. Pearson correlations were observed between distance travelled (DT), creatine kinase (CK), lactate dehydrogenase (LDH), ultimate pH (pHu), colour coordinates (L*, a* and b*) and Warner Bratzler Shear Force (WBSF). Principal component analysis (PCA) revealed that the 1st (pHu), 2nd (Tm) and 3rd (L*) principal components were the critical meat quality attributes. Positive relationships between carcass weights and beef quality characteristics for bovine cattle where the cumulative percentage of the first six principal component`s (PC`s) (SWT, WCW, CCW, DP, pHu and Tm contributed to 93.4 % of the total variance. Significant correlation coefficients between DT (r = 0.15), LDhr (r = 0.29), Ta (r = -0.52), Tm (r = 0.26), L* (r = 0.33), a* (r = 0.32) and WBSF (r = -0.49) were observed. Meat from Brahman (BR), Non-descript (ND) and Nguni (NG) cows had visible skeletal muscle fibres which were thin and long indicating improved tenderness of beef. Exposing animals to longer hours of transportation did not only reduce glucose levels but also increased the expression of HSPA1A and levels of cortisol. The CK and LDH were not related to beef quality. Therefore, CK and LDH can be used as indicators of animal welfare in slaughter cattle but cannot be used to predict the quality of meat. Bulls were the heaviest, although heifers had the highest dressing percentage than cows. Furthermore, the nanostructure of beef indicated that heifers had the best muscle fibres, sarcomere length and visible intercalated discs. The observed nanostructures of Nguni genotype are an indication of tender meat. Beef from heifers of Nguni had visible and tender meat with traces of intramuscular fat while males had shorter sarcomere length and tougher meat.