【作者】 姚焰础；

【导师】 卢德勋；

【作者基本信息】 内蒙古农业大学 ， 动物营养与饲料科学， 2008， 博士

【摘要】 本文选用体重约10kg的苏尼特羯羊16只,参照我国肉用绵羊饲养标准(NY/T 816-2004)进行舍饲,分别于体重10kg、20kg、30kg和40kg时选择4只接近目标体重的羊屠宰,研究了10～40kg羔羊肌内脂肪(IMF)随时间的沉积规律、肉质变化规律及IMF与肉质的相关性;采用荧光定量RT-PCR技术,检测了体重10kg、20kg、30kg和40kg羔羊肌内脂肪细胞分化转录因子——过氧化物酶体增殖物激活受体γ(PPARγ)与脂肪细胞定向和分化因子1(ADD1)、肌内前体脂肪细胞标志分子——前体脂肪细胞因子1 (Pref-1)和肌内脂肪代谢关键酶——乙酰辅酶A羧化酶(ACC)、脂肪酸合成酶(FAS)、脂蛋白酯酶(LPL)及激素敏感酯酶(HSL)的mRNA水平,揭示了羔羊肌内脂肪细胞分化相关因子和肌内脂肪代谢关键酶基因表达的发育规律及其与IMF的相关性。试验结果显示:1. 10～40kg苏尼特羔羊肌内脂肪含量和肌肉系水率随体重增加而升高(p<0.05),肌肉水分含量和剪切力随体重增加而降低(p<0.05);肌肉剪切力与肌内脂肪含量呈极显著负相关(r=-0.983, p<0.01)。2. 10～40kg苏尼特羔羊肌内PPARγ、ADD1和Pref-1基因表达量均呈下降趋势,体重10kg和20kg时的表达量显著高于30kg和40kg(p<0.05);Pref-1的mRNA表达量与IMF呈显著负相关(r=-0.659, p<0.05)。3. 10～40kg苏尼特羔羊肌内ACC和LPL基因表达量逐渐上升,30kg时表达量显著高于10kg (p<0.05),40kg时较30kg又有显著增加(p<0.05);ACC和LPL的mRNA表达量与IMF呈极显著(r=0.775, p<0.01)或显著(r=0.758, p<0.05)正相关。4. 10～40kg苏尼特羔羊肌内FAS和HSL基因表达量均呈下降趋势,体重30kg和40kg时的表达量显著低于10kg和20kg (p<0.05)。试验结果表明:随着体重增加,苏尼特羔羊肌内脂肪细胞分化能力逐渐减弱,肌内脂肪合成逐渐增强,肌内脂肪分解逐渐减弱;脂肪细胞分化对IMF沉积的贡献随体重增加而下降,脂肪细胞中脂质的积累是IMF不断上升的主要因素。更多还原

【Abstract】 16 castrated Sunit lambs with about 10kg BW were selected and yard-fed. The dietary nutrient levels for the lambs were arranged according to the recommendations of NY/T 816-2004 (Feeding standard of meat-producing sheep and goats). Four animals were slaughtered at 10kg, 20kg, 30kg and 40kg live weight respectively, and Longissimus Dorsi was sampled for further analysis. Intramuscular fat content and shear value were determined to study the developmental pattern of intramuscular fat and the relationship between intramuscular fat and meat quality. PPARγand ADD1 have been implicated as key regulators of adipocyte differentiation while Pref-1 is the marker of preadipocyte. It is well-known that ACC, FAS, LPL and HSL are key enzymes in lipid metabolism. The mRNA levels of these genes were determined to study the developmental expression of the genes involved in intramuscular adipocyte differentiation and of key enzymes involved in intramuscular fat metabolism in Sunit lambs by means of quantitative real-time RT-PCR.The results showed that:1. Intramuscular fat content and water-holding percentage increased as lambs grew while water content and shear value decreased. There was very significant negative correlation between shear value and intramuscular fat content of mutton (r=-0.983, p<0.01).2. There was a decreasing tendency of the developmental expression of PPARγ, ADD1 and Pref-1 genes from 10- to 40 kg BW. The mRNA levels of PPARγ, ADD1 and Pref-1 in 10- and 20kg lambs were significantly higher than that in 30- and 40kg lambs (p<0.05). There was significant negative correlation between Pref-1 mRNA abundance and IMF content (r=-0.659, p<0.05).3. As lambs grew, the mRNA levels of ACC and LPL genes increased. Their mRNA levels of 30kg lambs were higher than that of 10kg sheep while lower than that of 40kg lambs (p<0.05). There was very significant or significant positive correlation between ACC or LPL mRNA abundance and IMF content (r=0.775, p<0.01; r=0.758, p<0.05).4. The developmental expression of FAS and HSL genes decreased as lambs grew. Their mRNA levels in 10- and 20kg BW lambs were significantly higher than that in 30- and 40kg lambs.The results suggested that:Intramuscular adipocyte differentiation and IMF degradation in Sunit lambs decreased while IMF synthesis enhanced as lambs grew. In older animals IMF deposition was effected mainly by lipid accumulation in differentiated adipocytes rather than by adipocyte differentiation.更多还原