两种饲养方式对苏尼特羊肉脂肪酸组成和脂肪代谢相关基因表达的影响

本实验分别选取放牧条件和舍饲条件下饲养12 个月的苏尼特羊各10 只（公母各5 只），利用气相色谱-质谱法和实时荧光定量聚合酶链式反应法测定不同饲养方式下苏尼特羊股二头肌脂肪酸组成和脂肪代谢相关基因表达差异，研究不同饲养方式下脂肪代谢相关基因对脂肪酸组成的影响。结果表明：放牧组羊肉饱和脂肪酸相对含量显著低于舍饲组（P＜0.05），单不饱和脂肪酸相对含量显著高于舍饲组（P＜0.05），多不饱和脂肪酸中α-亚麻酸、共轭亚油酸、二十碳五烯酸和二十二碳六烯酸相对含量均显著高于舍饲组（P＜0.05）；放牧条件下股二头肌的固醇调节元件结合蛋白基因表达量显著低于舍饲条件下（P＜0.05）；放牧条件下股二头肌二酰基甘油酰基转移酶、激素敏感酯酶、脂肪酸脱氢酶2基因表达量均显著高于舍饲组（P＜0.05）；同时PPARγ基因表达量与饱和脂肪酸含量呈显著负相关（P＜0.05）。由此可见，从脂肪酸的角度来讲，放牧组肌肉营养价值更高，今后可通过调控脂肪酸代谢相关基因表达来改善舍饲羊营养品质。

Effects of Two Feeding Regimens on Fatty Acid Composition and Lipid Metabolism-Related Gene Expression in Sunit Sheep

The effect of different feeding systems on fatty acid composition and lipid metabolism-related gene expression in Biceps femoris from Sunit sheep was investigated. A total of 20 twelve-month-old sheep were allocated to two feeding regimens with 10 animals each (half each gender): grazing and stall feeding. Fatty acid composition was determined by gas chromatography-mass spectrometry. The expression of fatty acid synthase (FASN), sterol regulatory element binding protein1-c (SREBP1-c), diacylglycerol acyltransferase (DGAT), peroxisome proliferators-activated receptors γ (PPARγ), hormone sensitive lipase (HSL), lipoprotein lipase (LPL), fatty acid dehydrogenase 1 (FADS1) and fatty acid dehydrogenase 2 (FADS2) genes was evaluated by real-time quantitative polymerase chain reaction. The results showed that meat from grazing sheep had significantly lower amounts of saturated fatty acids than stall-fed sheep (P < 0.05). The contents of palmioleic acid and oleic acid as monounsaturated fatty acids and the contents of α-linolenic acid, conjugated linoleic acid, eicosapentaenoic acid and docosahexaenoic acid as unsaturated fatty acids were significantly higher than in the stall-fed group (P < 0.05). The expression of SREBP1-c gene was significantly lower in the grazing group (P < 0.05) whereas the expression of DGAT, HSL, and FADS2 genes were significantly higher compared with the stall-fed group (P < 0.05). The expression of PPARγ gene and saturated fatty acid content had a significantly negative correlation with each other (P < 0.05). Thus, in terms of fatty acid composition, meat from grazing animals had a higher nutritional value. Furthermore, the nutritional quality of meat from stall-fed sheep could be improved by regulating the expression of fatty acid metabolism-related genes.