【作者】 万发春；

【导师】 王加启；

【作者基本信息】 中国农业科学院 ， 动物营养与饲料科学， 2005， 博士

【摘要】 本研究利用利木赞×鲁西黄牛阉牛,通过完全随机区组设计研究了日粮VA添加水平对牛肉品质的影响及其机理。16头12月龄阉牛（BW:306±14.2kg）育肥90d,16头（BW:309±13.7kg）育肥180d,16头24月龄阉牛（BW:421±19.5kg）育肥90d,每个试验的阉牛都平均分为四组,饲喂同一基础日粮,日粮VA的添加水平分别为0、1100、2200和4400IU/kg饲料（干物质）。结果表明,0和1100IU的日粮VA添加水平显著增加了阉牛背最长肌和臀中肌的肌内脂肪含量,明显改善了12月龄阉牛的大理石花纹、色泽、抗氧化能力、嫩度和系水力,降低了背膘厚和滴水损失,对增重等其他性状没有明显影响;对于24月龄阉牛0和1100IU的日粮VA添加水平改善牛肉色泽、抗氧化能力和系水力的效果不如4400IU的日粮VA添加水平。0IU的日粮VA添加水平改善牛肉品质的效果不如1100IU,超过150d时还会严重影响阉牛的健康。日粮不同VA添加水平对阉牛血液中胰岛素、胰高血糖素、生长激素、T₃和皮质醇的浓度,肝脏、血液中VA和VE的含量,背最长肌、臀中肌、背部皮下脂肪、肠系膜脂肪中VA、VE的含量和LPL、HSL、FAS的活性,背最长肌、臀中肌中ACC、FAS、HSL、LPL和PPARγ的mRNA含量都有明显影响;对肝脏、血液中视黄酸的含量,背最长肌、臀中肌、背部皮下脂肪、肠系膜脂肪中视黄酸和cAMP的含量没有明显影响。VA对脂肪代谢过程的调节主要是通过改变胰岛素的分泌、LPL、HSL的活性和ACC、FAS、PPARγ的mRNA含量。VA改变HSL、LPL的活性不是通过cAMP介导的磷酸化和去磷酸化作用。 用12月龄利木赞×鲁西黄牛公牛的背部皮下脂肪细胞体外培养,诱导分化后用含有视黄酸、视黄醇或棕榈酸视黄酯50μg/dl的无血清培养基培养,每12h测定一次培养基中添加物的含量,连续测定96h。结果表明,在培养开始时培养基中视黄酸和视黄醇的浓度下降很快,36h后视黄酸浓度的下降速度趋势,而视黄醇的浓度在培养12h后出现一个较长时间的缓慢增加,72h后再次快速下降,棕榈酸视黄酯的浓度一直保持缓慢下降。培养基中视黄酸的浓度（y, μg/dl）与培养时间（x, h）成负的幂相关,回归方程为y=0.4122x^-0.8286（R²=0.8959）,培养基中棕榈酸视黄酯的浓度（y, μg/dl）与培养时间（x, h）成负线性相关,回归方程为y=-0.0329x+0.4653（R²=0.9204）。 诱导分化48h的脂肪细胞在无血清培养基中添加0、0.5μg/dl、5μg/dl、25μg/dl、50μg/dl和100μg/dl的视黄酸、视黄醇或视黄酸棕榈酸酯,培养5d、10d和15d。结果表明,在培养基中添加不同水平的视黄酸、视黄醇和视黄酸棕榈酸酯对脂肪细胞中ACC、FAS、HSL、LPL和PPARγ的mRNA含量都有明显影响,不同添加浓度间和不同的VA类型间没有明显的规律性变化,但与不添加组相比,使ACC、FAS的mRNA含量先降后升,使HSL和PPAR的mRNA含量下降,使LPL的mRNA含量先升后降。VA在分子水平上改变相关酶和调节因子的基因表达是影响脂肪细胞脂肪代谢的重要途径。更多还原

【Abstract】 The effects of dietary vitamin A concentration on beef quality of Limousin X Luxi steers and its mechanisms were investigated in three experiments with randomized complete-block design. Sixteen 12 months old steers (BW: 306+ 14.2kg),sixteen 12 months old steers (BW: 309+ 13.7kg) and sixteen 24 months old steers (BW: 421 + 19.5kg) were divided averagely into four groups according to BW, and finished individually with the same basal diets for 90,180 and 90 days respectively. Four group steers were supplemented with 0, 1100, 2200 and 4400 IU/kg diet(dry matter) vitamin A respectively in the experiment. Results showed that 0 and 1100IU/kg diet vitamin A contents increased the intramuscular fat contents and improved marbling for all steers, also improved beef color, antioxidant ability, tenderness and WHC of longissimus dorsi(LD) and gluteus medius(GM), decreased back subcutaneous fat depths(BSFD) and beef drip loss(DL) significantly, and had no effects on the daily gain, feed utilization, eye muscle area, carcass yield, percentage of mesentery fat(MF) weight to slaughter weight, and beef chemical compositions for 12 months old steers. However, the diets without additional vitamin A more than 150 days depressed the effects of beef quality improvement and also influenced the steers health. The 1100IU/kg diet vitamin A supply was the best to improve beef quality and had no the negative effect on the steers health in the study. Different concentrations of Vitamin A in diet influenced significantly the contents of insulin, glucagons, GH, T3 and cortisol in blood, the vitamin A and E concentrations in liver, serum, LD, GM, BSF and MF, the specific activity of LPL,HSL and FAS in LD, GM, BSF and MF, the mRNA contents of ACC, FAS, HSL LPL and PPARγ in LD and GM, not the retinoic acid concentrations in liver, serum, LD, GM, BSF and MF, and the cAMP content in LD, GM, BSF and MF. The effects of vitamin A to adipogenesis were regulated through the changes of insulin secretion, LPL and HSL activities, and mRNA content of ACC, FAS and PPARγ. The specific activity of LPL and HSL were not regulated by cAMP-dependent phosphorylation and dephosphorylation pathway.The adipocytes obtained from back subcutaneous adipose tissues of 12 months Limousin X Luxi crossbred bulls were cultured in vitro with differential inducing culture solution which were replaced with serum-free culture solution containing retinoic acid, retinol or retinyl palmitate(50ug/dl) after 48h. The concentrations of the additaments in culture solution were mensurated per 12h during 96h. Results showed that concentrations of retinoic acid and retinol decreased rapidly at the beginning of the culture, and then concentrations of retinoic acid decreased slowly after cells were cultured for 36h, however, concentrations of retinol increased in 60h after the cells were cultured for 12h and then declined quickly again. The concentration of retinoic acid in culture solution had exponential correlation to culture time, the equation is y(concentration of retinoic acid in culture solution, μg/dl)=0.4122x(culture time,h)~-0.8286 (R2=0.8959). Concentration of retinyl palmitate in culture solution always decreased slowly and had linear correlation to culture time, the equation is y(concentration of retinyl palmitate in culture solution,ng/dl)= -0.0329x(culture time,h)+ 0.4653(R2=0.9204).更多还原