饲粮添加包被蛋氨酸和包被叶酸对杜寒杂交二代公羔生长性能、养分消化代谢和瘤胃微生物蛋白质合成的影响

本试验旨在研究饲粮添加包被蛋氨酸（coated methionine，CM）和包被叶酸（coated folic acid，CFA）对杜寒杂交二代公羔生长性能、养分消化代谢及瘤胃微生物蛋白质合成的影响。采用2×2完全随机试验设计，试验因素为按照试验动物体重添加CFA（0 mg，CFA-或4 mg·（kg·d）^-1，CFA+）和CM（0 g，CM-或0.1 g·（kg·d）^-1，CM+）。将40只体重相近（（30.08±1.34）kg）的4月龄杜寒杂交二代公羔随机分为4组，分别饲喂基础日粮（CM-&CFA-）、基础日粮+CFA 4 mg·（kg·d）^-1（CM-&CFA+）、基础日粮+CM 0.1 g·（kg·d）^-1（CM+&CFA-）、基础日粮+CFA 4 mg·（kg·d）^-1+CM 0.1 g·（kg·d）^-1（CM+&CFA+）。试验期85 d，其中预试期15 d，正试期70 d，在试验期结束前10 d开展消化代谢试验。试验结果表明：1）饲粮添加CFA显著提高了1~30 d平均日增重和饲料转化率（P<0.05），而添加CM仅显著提高了1~30 d饲料转化率（P=0.036），对1~30 d平均日增重无显著影响（P>0.05）；饲粮中添加CFA、CM显著提高了杜寒杂交二代公羔31~60 d和1~60 d平均日增重及相应阶段饲料转化率（P<0.05），二者对1~60 d饲料转化率具有显著互作效应（P=0.007）；2）饲粮添加CFA显著提高了干物质、有机物、中性洗涤纤维和酸性洗涤纤维的表观消化率（P<0.05），饲粮添加CM有提高有机物表观消化率的趋势（P=0.066）及增加干物质消化率的趋势（P=0.095），二者对养分消化率无显著互作效应（P>0.05）；3）饲粮添加CFA、CM显著降低了尿能排出量，显著提高了能量消化率和代谢率（P<0.05）；通过显著降低粪氮、尿氮及总排泄氮（P<0.05），从而显著提高了氮的表观消化率和沉积氮水平（P<0.05），且二者同时添加对减少氮排泄、提高氮消化率有显著互作效应（P<0.05）；4）饲粮添加CM、CFA显著提高嘌呤衍生物的尿排泄量，提高瘤胃微生物蛋白质合成量（P<0.05）。饲粮添加CM、CFA提高干物质和有机物表观消化率，改善总能消化率和代谢率，增加氮表观消化率和氮沉积量，促进杜寒杂交二代公羔的生长。

Effects of Coated Methionine and Folic Acid Supplementation in Ration on Growth Performance,Nutrients Digestibility,Rumen Microbial Protein Synthesis in Finishing Doper×Thin-tailed Han F2 Crossbred Male Lambs

This study was conducted to investigate the effects of coated methionine (CM) and coated folic acid (CFA) supplementation and their interactions on growth performance, nutrients apparent digestibility, energy and nitrogen metabolism, and synthesis of rumen microbial protein in finishing Doper×Thin-tailed Han F₂ crossbred male lambs. Forty Doper×Thin-tailed Han F₂ crossbred male lambs with similar body weight ((30.08 ±1.34) kg) and good condition were arranged into 4 groups in a randomized design with a 2×2 factorial arrangement. One factor was supplemented CFA (0 mg,CFA-or 4 mg·(kg·d)^-1,CFA+) in the diet according to the body weight of the experimental animals,and the other factor was supplemented CM (0 g,CM-or 0.1 g·(kg·d)^-1,CM+). The feeding experiment lasted for 85 days with 15 d of adaptation and followed by 70 d of trial period. A digestibility trial was performed 10 days before the end of the trial period. The results showed that:1) Average daily weight gain and feed conversion ratio were significantly improved during 1-30 d with CFA supplementation in the ration of finishing lambs(P<0.05); There was a significant effect of CM supplementation on increasing feed conversion ratio (P=0.036), but no significant effect on average daily weight gain (P>0.05) during 1-30 d;Average daily weight gain and feed conversion ratio were significantly increased during 31-60 d and 1-60 d with CFA or CM supplementation in the ration for finishing Doper×Thin-tailed Han F₂ crossbred male lambs (P<0.05). The significant interaction between CFA and CM supplementation was found in feed conversion ratio during 1-60 d (P=0.007). 2) The apparent digestibilities of dry matter, organic matter, neutral detergent fiber and acid detergent fiber were significantly increased by adding CFA in the ration (P<0.05), the apparent digestibility of organic matter was tended to increase with CM added in the ration (P=0.066), and the apparent digestibility of dry matter was tended to increased (P=0.095). There was no significant interaction effect on the apparent digestibility of the nutrients (P>0.05). 3) The addition of CFA or CM significantly decreased urinary energy loss, enhanced digestibility and metabolizability of energy (P<0.05). The apparent digestibility of nitrogen and the deposited nitrogen were significantly increased (P<0.05) by significantly reducing fecal nitrogen, urinary nitrogen and total excretion nitrogen (P<0.05). A significant interaction effect between CFA and CM addition was found in reduction of nitrogen excretion and elevation of nitrogen digestibility (P<0.05). 4) The addition of CFA or CM significantly increased the urinary excretion of purine derivatives and the synthesis of rumen microbial protein (P<0.05). The results showed that the addition of CM or CFA improved the digestibility of dry matter and organic matter, enhanced digestibility and metabolizable ratio of total energy, increased apparent digestibility of nitrogen and nitrogen deposition, thus promoted the growth of Doper×Thin-tailed Han F₂ crossbred male lambs.