饲喂不同蛋白水平日粮的牦牛瘤胃氮代谢与十二指肠各氮组分流量

采用瘘管手术方法对３头生长牦牛在饲喂代谢能ＭＥ均为９．６ＭＪ／ｋｇＤＭ，粗蛋白（ＣＰ）为８％和１２％的日粮时的复胃氮代谢与瘤胃、肠道消化代谢进行研究。试验结果表明，日粮ＣＰ水平升高后，生长牦牛瘤胃氨氮浓度由３．３升至５．９ｍｇ／１００ｍｌ（Ｐ＜０．０１），瘤胃内氮的消失率由１．９％升到２１．１％（Ｐ＜０．０１）。瘤胃微生物蛋白质合成效率基本不变（平均６９．１ｇＣｐ／ｋｇＤＯＭ）；一昼夜进入十二指肠的食糜量及食糜干物质量基本不变；食糜总氮、氨氮及非氨氮量均显著增加（Ｐ＜０．０１），其中非氨氮增加２０％：非氨氮中微生物氮的比例由４５％降至３９％（Ｐ＜０，０５）；日粮ＤＭ，ＯＭ，ＣＰ和ＡＤＦ整体消化率分别提高１２．９％、１３．４％、３４％和２２．３％（Ｐ＜０．０１）。日粮ＣＰ由８％升至１２％后，生长牦牛瘤胃ＴＶＦＡ中乙酸比例由５４％降至４３．５％（Ｐ＜０．０１）．丙酸比例由２４．８％升至２８．４％（Ｐ＜０．０５），丁酸比例也由２１．１％增至２８．５％（Ｐ＜０．０１）。同时Ｃ２／Ｃ３比由２．１９降至１．５４（Ｐ＜０．０１）。

RUMINAL NITROGEN METABOLISM AND THE FLOWS OF NITROGEN FRACTIONS REACHINGTHE DUODENUM OF GROWING YAKS FED DIETS CONTAINING DIFFERENT LEVEL OF CRUDE PRUDE PROTEIN

Three growing yaks fitted with cannulaes in the rumen and duodenum were used to study the nitrogen metabolism in the stomach . Feed were given in a 12 - hour intervals per day . Two diets containing 8a% and 12 % crude protein( CP) were given to the animals The diets were calculated to be isocaloric based on metabolizable energy (9 . 6MJ ME / kg) con- tent and to be composed of 50% straw and 50% concentrate. Ammonia nitrogen in rumen fluid for 8%and l2% CP diets were 3. 3 and 5. 9mg / 100ml respectively(P < 0. 01) . Corresponding mean Values for the rate of nitrogen disappearence in the stomach were 1. 9% and 21. 1% (P < 0. 01) and for the efficiency of synthesis of mi- crobial protein in the rumen were 69. 3 and 68. 9g CP per kg organic matter apparently di- gested(P > 0. 1) . Amounts of total nitrogen, ammonia nitrogen and non - ammonia nitrogen reaching the duodenum per day increased significantly while microbial nitrogen did .not change as the dietary CP concentrate increased . Among which , the non - ammonia nitrogen increased by 20% Apparent digestibilities of dry matter, organic matter, CP and acid de- tergent fiber in the whole tract increased by 12. 9% , 13. 4% , 34. 0% and 22. 3% respec- tivtely with increasing dietary CP, Total volatile fatty acid(TVFA) in rumen fluid for 8. and 12% CP diets were 1 . 145 and 1. 108 mM / 100ml respectively , no difference was found. But the percentages of acetic acid( AA) , Propionic acid(PA) and butyric acid(BA) in TVFA varied with diets. Corresponding mean values of AA for the diets were 54. 0% and 43. 5% ( p <0.0l),of PA were 24.8% and 28.5%(P<0.05),ofBA were 21.1% and 28.5.(P<0.0l) and of AA /PA were 2.l9 and 1. 54(P<0.01).