单宁酸对绵羊日粮养分消化利用及氮代谢的影响

Effects of tannic acid on digestion and utilization of nutrients and the metabolic parameters of nitrogen in sheep

通过在饲料中添加不同比例的分析纯单宁酸(鞣酸),对绵羊营养物质消化利用及氮代谢参数的影响进行了研究,并探讨分析纯单宁酸在饲粮中的适宜添加量。试验选用4只安装永久性瘤胃瘘管的羯绵羊(2岁,平均体重为35±2.15 kg)作试畜,采用4×4拉丁方设计进行试验,研究了饲粮单宁酸水平(A、B、C、D分别为0、10、15、20 g/kg DM)对绵羊养分消化利用与氮代谢参数的影响,16 d(预试期10 d,正试期6 d)为一个饲粮循环,全期共64 d。结果表明,高浓度单宁酸(20 g/kg DM)影响绵羊的采食量,进而影响绵羊对干物质(DM)、有机物(OM)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)的食入量(P<0.01);但随着单宁酸浓度的增加,绵羊对DM、OM、NDF、ADF、Ca、P的消化率并无显著影响(P>0.05);处理组A、B、C的N食入量与N消化量极显著高于D(P<0.01),N存留率随单宁酸比例的增大而升高,仅C处理组显著高于A(P<0.01);N消化率、p H、总N浓度差异不显著(P>0.05);而瘤胃液NH3-N浓度和尿素氮(BUN)呈线性下降,A的NH3-N显著高于D(P<0.05),而其血浆尿素氮(BUN)高于C、D(P<0.01)。可见,单宁酸具有提高蛋白质在绵羊体内消化吸收的功效;饲粮中单宁酸含量小于15 g/kg DM时,能够显著提高氮存留率,对蛋白质保护的效果较好;故单宁酸在饲粮中的添加量不应该超过15 g/kg DM。

An experiment was conducted to determine the effects of tannic acid on nutrient digestion and nitrogen metabolic parameters in sheep,in order to determine the appropriate amount of tannic acid in feed. Four fine-wool wethers（ two years old and average live weight of 35 ± 2. 15 kg） fitted with permanent rumen fistula were selected and a 4 × 4 Latin square design with 10 d preliminary and 6 d sampling experiment was used to study the effects of4 different tannic acid contents on nutrient digestion and nitrogen metabolic profiles. The contents of tannic acid in diets were 0（ A）,10（ B）,15（ C）,and 20（ D） g/kg DM. The results indicated that both feed intake and the intake of DM,OM,NDF and ADF were affected by the tannic acid in treatment D（ 20 g/kg DM）（ P〈0. 01）,while the digestibility of DM,OM,NDF,ADF,Ca and P was unaffected by the acid contents（ P〈0. 05）. The intake and digestion of N were higher in the A,B and C treatments than in treatment D（ P〈0. 01）. N retention increased as the level of tannic acid increased（ N retention in treatment C was higher than in treatment A）. No differences were observed in N digestibility,p H and total nitrogen in rumen fluids（ P〉0. 05）,whereas the levels of NH3-N and BUN decreased linearly. The level of NH3-N for diet A was higher than for D（ P〈0. 05） and BUN was higher in the C and D treatments（ P〉0. 01）. In conclusion,tannic acid increased rumen bypass proteins. N retention was improved when the ratio of tannic acid was less than 15 g/kg DM,suggesting that the optimal tannic acid content in diets is less than this ratio.