中文摘要：

在海拔3 980m的果洛州大武乡对3头牦犊牛分别饲喂100%的青贮披碱草（A）、40%精料＋60%青贮披碱草（B）、60%精料＋40%青贮披碱草（C）3种不同日粮,按3×3拉丁方设计了消化代谢试验。结果表明,1）日粮干物质、有机质、粗蛋白和能量消化率差异显著（P〈0.05）,粗灰分消化率差异不显著（P〉0.05）,且随日粮中精料比例的增加,各营养成分的消化率逐渐降低;2）日粮C的能量代谢率显著低于日粮A和日粮B（P〈0.05）,但消化能转化为代谢能的效率差异不显著（P〉0.05）,其平均转化效率为0.78;3）粪和尿中排出钙差异显著（P〈0.05）,粪中排出磷差异不显著（P〉0.05）,而尿中排出磷差异显著（P〈0.05）;钙存留量随日粮中精料比例的增加而减小,磷存留量在A日粮下最大。以上结果说明牦犊牛对日粮的消化和能量代谢与其组成密切相关,而且表观消化率随日粮水平的提高而降低,其能量转化率低于生长牦牛和成年牦牛。因此,该结果可为牦犊牛的补饲和快速育肥提供科学依据。

英文摘要：

A supplementary strategy and feedlotting method for yak calves was sought as a new approach to alleviate the pressure on natural grasslands and allow recovery of natural vegetation.A 3×3 Latin square test of digestive and metabolic trials was designed in Dawu township of Guoluo Prefecture.Three yak calves per treatment were fed with 3 different diets：（A） 100% Elymus nantus silage,（B） 40% concentrate＋60% E.nantus silage,and（C） 60% concentrate ＋40% E.nantus silage.1） There were significant differences in digestibility of dry matter,organic matter,crude protein and energy with the different diets,but there was no significant difference for crude ash.With an increase in percentage of concentrate in the diet,the digestibility of every nutrient ingredient in the different diets gradually decreased;2） The metabolizability of energy for diet C was significantly lower than that for diets A and B,but the efficiencies of digestive energy conversion into metabolic energy（ME/DE） were not significantly different between the 3 diets.The average conversion efficiency was 0.78;3） Calcium（Ca） extracted from faeces and urine was significantly different between the diets,while phosphorus（P） differed significantly from urine from the three diets but not from faeces.Ca sediment decreased with the increase in percentage of concentrate,but P sediment was maximum in diet A and minimum in diet B.These results showed that the digestive and energy metabolisms of diets for yak calves were closely bound up with dietary composition.Apparent digestibility decreased with an increase of dietary level.These result provide a scientific basis for supplementary feeding and celerity fattening,which would be an effective approach to speed up turnover of drove and to increase the merchandise ratio of yaks.