肥羔EAA需要量与小肠tdAA供应量及LAA顺序研究

Due to feedstuff variety and variability and to the remodeling of nutrient intake by the rumen microflora, the intestinal supply of truly digestible amino acid (tdAA) and its composition profile are dependent on the duodenal fluxes of rumen microbial crude protein (MCP) and rumen undegradable protein (RUP) fraction and their AA profiles under the practical production condition, respectively. However, the estimation of the intestinal flux of tdAA and its AA profiles is very difficult owing to the disturbing of endogenous crude protein (ECP) secretion in gastro-intestinal tract of ruminant animal. So, the question of how to define requirements of the protein/amino acid of ruminants and the supply of diet has been a world wide difficult and hot research area. In this research proposal, we plan to define the small-intestinal supply of truly digestible amino acids (tdAA) originating from MCP and RUP and the amino acid profile by means of evaluating the effective degradability of the ration of growing-finishing lambs firstly; determining the ruminal microbial crude protein production efficiency from the dietary rumen degradable protein and total digestible nutrients as well as the intestinal digestibility secondly; then measuring the intestinal truly digestibility of rumen undegradable protein fraction of the ration for lambs thirdly; then quantifying the total secretion of endogenous crude protein and its intestinal digestibility of lambs finally by the stable isotope label dilution technique with 15N-leucine being the endogenous protein tracer. On the basis of these results, the requirements of essential amino acids (EAA) and their limitation sequences will be established by the application of indicator amino acid oxidation technique combined with typical nitrogen balance trial by using 13C-indicator amino acid. The final goal of our research project is to establish an intestinal truly digestible amino acid ideal pattern for the growing-finishing lambs with a higher growing-finishing rate and optimal conversion efficiency of feed nitrogen to guide the lamb production. The potential value of this research project is to provide a scientific basis and giddiness for increasing the utilization efficiencies of local protein feed resources, increasing the economic benefits of lamb industrial production, reducing the environmental pollution of excretory nitrogen in future.

由于反刍动物饲料的多样性及瘤胃微生物对摄入养分的重新塑造，因此，反刍动物小肠真可消化氨基酸(tdAA)的供应量及组成在实际生产条件下取决于MCP和RUP的供应量及AA组成，但其准确评定受到ECP分泌量的干扰，导致反刍动物的AA需要量与供应量的研究成为一个难点和热点问题。本项目拟通过评定肥羔饲粮的瘤胃有效降解率、瘤胃MCP合成效率及小肠消化率、RUP的小肠真消化率，采用稳定性同位素15N-Leu标记物稀释技术评定ECP分泌量等途径来评定肥羔在实际生产条件下小肠tdAA的供应量及组成比例。在此基础上，采用13C-指示氨基酸氧化技术结合氮平衡法研究肥羔EAA的需要量及小肠MP中LAA顺序，以期建立一种增重水平高、饲粮氮利用效率最佳的小肠tdAA理想模式，为实现肥羔氨基酸营养的供需平衡，提高肥羔肉的产量和品质，增加肥羔生产的经济效益，节省蛋白质饲料资源，减少排泄物中氮排放量提供科学依据。

本项目采用瘤胃固相和液相食糜双标记物技术，测定出育肥羔羊在实际饲喂状态下瘤胃固相和液相食糜的外流速度（Kp）分别为1.84%/h和12.33%/h。全收尿并测定尿样中嘌呤衍生物（PD）含量，并根据RDP和TDN的实际进食量计算瘤胃MCP的转化效率。结果表明，增加RDP采食量可显著提高瘤胃MCP的合成量，且RDP采食量与MN/DOMR之间存在显著的正相关（R2 = 0.9994, P = 0.0109），但MCP的合成效率不受影响（P>0.05）。.利用移动尼龙袋技术（MBT）和体外三步法（TSP）评定了3种全混合饲粮中RUP-AA小肠真消化率。结果表明：对DM和CP在瘤胃降解率不受日粮CP水平的影响，而小肠的消化率随饲粮CP水平的提高而显著增高。His被瘤胃微生物大量降解，而Tyr的降解率最低。除Thr、Trp、Ala、Asp和Pro之外，3种饲粮的其他AA的瘤胃降解率无显着性差异。.15N-Leu 连续灌注的试验结果表明，育肥羔羊在实际饲喂条件下，增加干物质采食量对十二指肠内源氮的流量没有影响，但回肠末端内源氮的流量随采食量的增加而显著升高，DMI从736g/d增加到1100 g/d时，内源氮占总氮流量的比例从12%升高到37%。内源氮的比例占总氮量的30%以上。.用瘤胃内连续灌注双标记物溶液的方法，测定了育肥羔羊在饲喂3种全混合日粮条件下小肠DM、N及AA流通量和小肠消化率。结果表明，提高日粮CP/RDP水平可显著提高育肥羔羊氮的进食量、全消化道表观消化率和N沉积，对小肠食糜流量及氨基酸吸收率无显著性影响，但有增加十二指肠总N和TAA流量以及EAA中Arg、His和Lys的吸收率的趋势。.氮平衡测定结果表明，育肥羔羊的前三位限制性氨基酸分别为Arg、Met和Lys。以13C-Phe作为指示剂氨基酸，在确定了灌注剂量（5.32 mg/kg-BW）和呼出气中13CO2达到稳态的时间范围（灌注开始后的2-3h）的基础上，进行IAAO测定，先后评定出育肥羔羊对小肠可代谢Arg、Met和Lys的最低需要量分别为7.84、2.02和6.38 g/day。据此提出了育肥羔羊小肠可代谢氨基酸的理想比例模式1套。本项目成果为进一步研究制定提高饲粮蛋白质的利用效率、降低粪尿排泄物中氮的排放量的营养调控措施和日粮配合技术提供了试验依据和研究方法。