1School of Veterinary & Life Sciences,Murdoch University,Murdoch,WA 6150,Australia.
2School of Environmental & Rural Science,University of New England,Armidale,NSW 2351,Australia.
Animal. 2019 Jul;13(7):1468-1477. doi: 10.1017/S1751731118003075. Epub 2018 Nov 16.
Under current Australian industry pre-slaughter guidelines, lambs may be off feed for up to 48 h before slaughter. The purpose of this study was to examine what proportion of circulating metabolites at slaughter are due to stress and feed deprivation and if this response differs between Merino and Terminal genotypes. In addition the effect of feed deprivation on carcass weight and meat quality was examined. Jugular blood samples were collected from 88 Merino and Terminal sired lambs at rest and at slaughter following 24, 36 and 48 h of feed deprivation and plasma analysed for glucose, lactate, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHOB). From the same carcasses hot carcass weight (HCWT) were measured as well as a suite of meat quality traits measured such as M. longissimus lumborum (loin) and M. semitendinosus pH at 24 h postmortem. Loin samples were also analysed for intramuscular fat content and Warner-Bratzer Shear Force. Merino sired lambs had a higher NEFA response compared to Terminal sired lambs at slaughter after 24, 36 and 48 h of feed deprivation, with NEFA levels up to 35% higher than previously reported in the same animals at rest in animal house conditions, whereas BHOB response to feed deprivation was not affected by sire type (P>0.05) and similar to previously reported at rest. In addition to the metabolic effects, increasing feed deprivation from 36 h was associated with a 3% reduction in HCWT and dressing percentage as well as causing increased ultimate pH in the M. semitendinosus in Merino sired lambs. Findings from this study demonstrate that Merino and Terminal sired lambs differ in their metabolic response to feed deprivation under commercial slaughter conditions. In addition, commercial feed deprivation appears to have a negative effect on ultimate pH and carcass weight and warrants further investigation.
在澳大利亚现行的宰前行业指南下，羊只可能在宰前禁食长达 48 小时。本研究的目的是检测宰前应激和禁食对循环代谢物的影响比例，以及这种反应是否在美利奴羊和终端品种之间存在差异。此外，还研究了禁食对胴体重和肉质的影响。在 24、36 和 48 小时禁食后，从 88 只美利奴羊和终端品种公羊中休息和宰前采集颈静脉血样，并分析血浆中的葡萄糖、乳酸、非酯化脂肪酸（NEFA）和β-羟丁酸（BHOB）。从同一胴体中测量热胴体重（HCWT），以及一系列肉质性状，如 24 小时宰后背最长肌（腰肉）和半腱肌 pH 值。还分析了腰肉样本中的肌内脂肪含量和华纳-布拉泽剪切力。与终端品种公羊相比，美利奴品种公羊在 24、36 和 48 小时禁食后宰前的 NEFA 反应更高，禁食后 NEFA 水平比之前在相同动物的动物房条件下休息时高 35%，而 BHOB 对禁食的反应不受 sire 类型的影响（P>0.05），与之前的报告相似。除了代谢影响外，从 36 小时增加禁食会导致 HCWT 和出肉率降低 3%，并导致美利奴品种公羊半腱肌的最终 pH 值升高。本研究的结果表明，在商业屠宰条件下，美利奴羊和终端品种公羊对禁食的代谢反应存在差异。此外，商业禁食似乎对最终 pH 值和胴体重有负面影响，需要进一步研究。
