低蛋白饲粮补充4种氨基酸对肉用羊增重与肉质中氨基酸含量及血清学的影响

Effects of supplementation of amino acids in low-protein diets on weight gain,serum protein index and amino acid content in meat of fattening mutton sheep

本试验旨在研究不同水平低蛋白饲粮补充过瘤胃氨基酸对育肥杜寒杂交肉用母羊增重、血清中蛋白与激素指标、肌肉中氨基酸含量和肉品质的影响,探索育肥肉羊饲粮低蛋白质含量的理论价值和应用效果。选用150只体重相近4月龄育肥杜寒杂交肉用母羊,随机分成5组,每组3个重复,每个重复10只羊。对照组饲喂粗蛋白质水平为16%的饲粮,试验组饲喂氨基酸平衡低蛋白饲粮,分为LP14组(饲粮CP=14%)、LP12组(饲粮CP=12%)、LP10组(饲粮CP=10%)和LP12+NPN组(饲粮CP=12%,添加1%尿素),各试验组饲粮中都添加过瘤胃赖氨酸、蛋氨酸、苏氨酸和精氨酸,使其和对照组饲粮中这4种氨基酸的含量保持一致,试验期90 d。结果表明:(1)不同水平的低蛋白饲粮在补充过瘤胃氨基酸后,对育肥杜寒杂交肉用母羊的试验末重、净增重和饲料转化比均无显著性影响(P>0.05),对照组干物质采食量高于各试验组(P<0.01),LP12+NPN组育肥羊干物质采食量高于其他低蛋白组(P<0.01)。(2)各组间试验羊血清总蛋白(TP)、球蛋白(GLB)、生长激素(GH)、类胰岛素样生长因子I(IGF-I)均无显著性差异(P>0.05),低蛋白组育肥羊血清尿素氮(BUN)显著低于对照组(P<0.01)。(3)各组肉羊背最长肌在肉色、滴水损失、pH0、pH24、熟肉率以及剪切力上均差异不显著(P>0.05)。(4)各组间试验羊的背最长肌中氨基酸的含量差异不显著(P>0.05)。在本试验条件下,降低育肥杜寒杂交肉羊饲粮粗蛋白质水平1~4个百分点并补充过瘤胃赖氨酸、蛋氨酸、苏氨酸、精氨酸和尿素,不会影响其增重情况、血清指标和肉品质,即低蛋白饲粮补充过瘤胃氨基酸可以满足肉羊育肥阶段的营养需要。

The aims of the present study were to investigate the effects of low-protein diets of different levels supplemented with rumen-protected amino acids on weight gain,contents of protein and hormone in serum,amino acid content of muscle,and meat quality in Dorper×thin-tailed Han crossbred ewes,which was used to develop the theoretical basis of low protein level diet in sheep production.A total of 150 Dorper×thintailed Han crossbred ewes,with four-month-old and an average body weight of 33 kg,were randomly divided into 5 groups,with 3 replicates in each group and 10 sheep per replicate.Sheep in control group were fed diet with crude protein(CP)content of 16%.Animals in 4 experimental groups were fed low protein diets with amino acid balanced,which were LP14 group(14%CP of DM basis),LP12 group(12%CP),LP10 group(10%CP)and LP12+NPN group(12%CP plus 1%urea,DM basis).In these 4 low protein diets,the contents of amino acids were balanced by rumen-protected lysine,methionine,threonine and arginine,and were consistent with the contents of amino acids in control.The experimental period was 90 days.The results showed that:(1)Low-protein diets of different levels supplemented with rumen-protected amino acids had no significant effect on the final body weight,body weight gain and feed conversion ratio in Dorper×thin-tailed Han crossbred ewes(P>0.05).Dry matter intake of the control group was higher than that of the experimental groups(P<0.01).However,dry matter intake of sheep in the LP12+NPN group was higher than that of the other low protein groups(P<0.01).(2)There was no significant difference in serum concentrations of total protein(TP),globin(GLB),growth hormone(GH)and insulin-like growth factor-I(IGF-I)among the 5 groups(P>0.05).However,blood urea Nitrogen(BUN)concentrations in the low-protein groups were significantly lower than that of control group(P<0.01).(3)There was no significant difference among the 5 groups in the length of longissimus dorsi muscle,in terms of flesh color,drip loss,pH0,pH24,cooked meat rate and shearing force(P>0.05).(4)There was no significant difference in amino acid content of longissimus muscle in sheep among the 5 groups(P>0.05).Under the conditions of this experiment,reducing the crude protein level of fattening Dorper×thin-tailed Han crossbred ewes diet by 1~4 percentage points and supplementing rumen lysine,methionine,threonine,arginine and urea had no effect on its body weight gain,serum indicators and meat quality.This test proved that supplementing rumen amino acids with low-protein diets could meet the protein requirements of fattening sheep.