Abstract:

In order to study the difference of meat quality and the expression characteristics of meat quality-related genes in Tibetan sheep at different altitudes， the meat quality and nutritional components of longissimus dorsi， triceps brachii and biceps femoris of Tibetan sheep at altitude 2 500， 3 500 and 4 500 m were determined， and the expression levels of meat-related genes （H-FABP， LPL， MC4R and CAST） were determined and their correlations were analyzed. The results showed that the Tibetan sheep meat of low altitude had lower shearing force， lower water loss rate， higher tenderness and better taste， especially longissimus dorsi was better than the other 2 parts. The Tibetan sheep meat of high altitude had higher cooked meat rate and higher meat yield. The contents of mineral and crude protein in high altitude Tibetan sheep meat were higher， while the low altitude Tibetan sheep meat was more succulent. Compared with the two leg muscles， the longissimus dorsi had better taste. The expression levels of genes related to meat quality were differences among different altitudes. Among them， H-FABP had the highest expression levels in different muscles at mid-altitude， and LPL， MC4R and CAST had the highest expression levels in biceps femoris of Tibetan sheep at low altitude， and was higher in the longissimus dorsi of Tibetan sheep at middle and high altitude. The correlation analysis showed that the expression levels of H-FABP， LPL， MC4R and CAST genes were significantly correlated with cooked meat rate， shear stress， water loss rate， ash， crude fat， crude protein and dry matter in Tibetan sheep. It showed that the meat quality and nutritional components of Tibetan sheep at different altitudes were different， and the expression levels of meat-related genes in different parts were also different， which affected the meat quality of Tibetan sheep. Above results provided basis for meat selection and genetic improvement of Tibetan sheep at different altitudes.

Key words: Tibetan sheep, different altitude, meat quality, nutritional composition, gene expression

摘要：

为探究不同海拔藏绵羊肉品质差异及肉质相关基因的表达特征，以来自海拔2 500、3 500和4 500 m藏绵羊为研究对象，对其背最长肌、臂三头肌和股二头肌的肉品质及营养成分进行测定，并对背最长肌和股二头肌肉质相关基因（H-FABP、LPL、MC4R和CAST）的表达量进行测定及相关性分析。结果表明，在肉品质方面，低海拔藏绵羊肉的剪切力小、失水率低、嫩度高、口感更好，尤其背最长肌要优于其他2个部位，而高海拔藏绵羊的熟肉率和出肉率更高；在营养物质方面，高海拔藏绵羊肉的无机盐、粗蛋白含量较高，更具营养价值，但低海拔藏绵羊肉的多汁性好，且背最长肌的口感、营养成分均好于腿肌。肉质相关基因的表达量在不同海拔间存在差异，其中，H-FABP在中海拔藏绵羊各部位肌肉中的表达量均最高；LPL、MC4R、CAST在低海拔藏绵羊股二头肌中的表达量均最高，在中、高海拔藏绵羊背最长肌中的表达量较高。相关分析表明，H-FABP、LPL、MC4R、CAST基因的表达量与藏绵羊的熟肉率、剪切力、失水率及灰分、粗脂肪、粗蛋白、干物质含量显著相关。由此可见，不同海拔藏绵羊的肉质、营养成分均存在较大差异，且不同部位中肉质相关基因的表达量也存在差异，从而影响藏绵羊的肉质。以上结果为不同海拔藏绵羊的肉品选择及遗传改良提供基础。

关键词: 藏绵羊, 不同海拔, 肉品质, 营养成分, 基因表达