茶渣单宁含量对绵羊养分消化利用与氮代谢参数的影响

旨在研究茶渣单宁含量对绵羊养分消化利用与氮代谢参数的影响.本研究分析了茶渣(RTL)的营养成分和单宁含量；用体外法测定6种配比茶渣/大豆粕混合料(0∶10、1∶9、2∶8、3∶7、4∶6、10∶0,其中茶渣缩合单宁(RTL-CT)含量依次为0.00、0.16、0.31、0.47、0.63和1.57 g·kg -1DM)的瘤胃液与瘤胃液+HCl-胃蛋白酶干物质(DM)与粗蛋白质(CP)降解率( rdDM、tdDM、rdCP、tdCP)；用4只安装永久性瘤胃瘘管的甘肃高山细毛羊羯羊(1岁半,体质量(29士2.55)kg),按4×4拉丁方方案进行试验,研究了饲粮RTL-CT水平(A、B、C、D分别为0.00、0.77、1.53、2.30 g·kg-1DM)对绵羊养分消化利用与氮代谢参数的影响,共4个15d的饲粮循环(预试期9d,收集期6 d).试验结果:(1)3个茶渣样的粗蛋白质(CP)、粗纤维(CF)、单宁(单宁酸等价,TAE)与CT含量范围分别为23.23％～28.11％、16.68％～17.84％、1.98％～2.10％和1.47％～1.57％.(2)茶渣/大豆粕混合料的rdDM、tdDM、rdCP、tdCP均随茶渣比例提高而线性下降,变化范围相应为61.39％～25.67％、79.61％～26.47％、60.76％～16.68％和84.85％～17.69％.(3)体内试验中,高比例茶渣影响采食量,饲粮D(P＜0.01)、C(P＞0.05)的DM与有机物质(OM)采食量低于A、B; RTL-CT对DM、OM、中性洗涤纤维、酸性洗涤纤维、氮、钙和磷的消化率无显著影响(P＞0.05)；但随RTL-CT水平提高尿氮排出量线性下降,导致氮存留率上升,C的氮存留率较A提高23.61％ (P＜0.05),B、D分别提高12.57％和15.88％ (P＞0.05)；随RTL-CT提高,瘤胃液pH、总氮浓度无显著变化(P＞0.05),而NH3-N与血浆尿素氮(BUN)含量线性下降,C、D的NH3-N分别是A的50.36％( P＞0.05)和46.55％ (P＜0.05),BUN相应为A的68.04％与59.99％(P＜0.05).可见,茶渣是高蛋白质、低纤维物质,单宁含量为中等的物质；本试验中,RTbCT降低了饲粮的体外瘤胃CP降解率,但未影响体内全消化道消化率,且通过减少尿N排出而提高了氮存留率；但高比例RTL-CT降低了绵羊采食量.显然,RTL-CT l.53 g·kg-1DM对饲粮蛋白质的保护效果较好,且对采食量无显著影响.

Effects of Tannin Content in Residue of Tea-leaves on Digestion and Utilization of Nutrients and Metabolic Parameters of Nitrogen in Sheep

The present experiment was conducted to determine the effects of tannin content in residue of tea-leaves(RTL) on digestion and utilization of nutrients and metabolic parameters of nitrogen in sheep.The contents of nutrients and tannin in RTL were analysed;The in vitro degradability(rdDM、tdDM、rdCP、tdCP) of dry matter(DM) and crude protein(CP) of mixtures with six ratio of RTL to soybean meal(0:10,1:9,2:8,3:7,4:6,10:0),which levels of RTL condensed tannin(RTL-CT) of the mixtures were 0.00,0.16,0.31,0.47,0.63,1.57 g·kg-1DM,respectively,was measured by incubating in rumen fluid and rumen fluid + HCl-pepsin.To study the effects of RTL-CT contents on digestion and utilization of nutrients and metabolic profiles of nitrogen in sheep,four High Mountain Fine-wool wethers(one and a half years old and average live weight of(29±2.55)kg) fitted with permanent rumen fistula and a 4×4 Latin square design with four cycles of diet each of 9 d for preliminary followed 6 d for sampling were used in this experiment.The contents of RTL-CT in diets were 0.00(A),0.77(B),1.53(C),2.30(D) g·kg-1DM.The results showed that:(1) the range of contents of CP,crude fiber(CF),TAE(tannic acid equivalent) and CT in three samples of TRL were 23.23%-28.11%,16.68%-17.84%,1.98%-2.10%,1.47%-1.57%,respectively.(2) The degradabilities of DM and CP of the mixtures in rumen fluid and rumen fluid + HCl-pepsin(rdDM,tdDM,rdCP,tdCP) decreased linearly as the contents of RTL-CT,the range of change were 61.39%-25.67%,79.61%-26.47%,60.76%-16.68%,84.85%-17.69%,respectively.(3) In vivo,the intake of diet was affected by high-raito of RTL,compared with diet A and B,the intakes of DM and organic matter(OM) of diet C(P>0.05) and diet D(P<0.01) were lower;the digestibilities of DM,OM,calcium(Ca),phosphorus(P),neutral detergent fiber(NDF) and acid detergent fiber(ADF) of diets were unaffected by the contents of RTL-CT(P>0.05).But the excretions of urinary nitrogen were decreased linearly and retention of N increased as the RTL-CT level,the retention of nitrogen of diet B,C,D were raised by 12.57%(P>0.05),23.61%(P<0.05) and 15.88%(P>0.05)than for diet A,respectively;there were no significant changes of the levels of pH and total nitrogen of rumen fluid(P>0.05) as the levels increasing of RTL-CT,while the contents of NH3-N and plasma urea nitrogen(BUN) linearly decreased,the levels of NH3-N and BUN of diet C and D were 50.36 %(P>0.05),46.55%(P<0.05)and 68.04%,59.99%(P<0.05)lower than that of diet A,correspondingly.It follows that residue of tea-leaves were a matter with high-protein,low-fiber and middle content of tannin;under the condition of this experiment,the in vitro rdCP were decreased by RTL-CT,but the digestibilities of CP in total gastrointestinal tract were unaffected by levels of RTL-CT,and N retentions were increased owing to reducing of the excretion of N in urine as RTL-CT;yet high ratio of residue of tea-leaves in diet resulted in lowing of intake by sheep.Obviously,the protection effect of RTL-CT with 1.53 g·kg-1DM on protein was better,but no significant effect on the intake of diet.