Beever D E, Gill M, Dawson J M, Buttery P J
AFRC Institute for Grassland and Animal Production, Hurley Research Station, Maidenhead, Berks.
Br J Nutr. 1990 May;63(3):489-502. doi: 10.1079/bjn19900136.
The effect of two levels of fishmeal substitution (50 (FM1) and 150 (FM2) g/kg) of a grass silage control diet (C) on the rumen digestion of organic matter and nitrogen, and the small intestinal disappearance of amino acids was examined in young growing cattle each equipped with simple PVC cannulas in the dorsal sac of the reticulo-rumen, the proximal duodenum and the terminal ileum. The silage was a primary growth of perennial ryegrass (Lolium perenne) (+formic acid) with a total N content of 22 g/kg dry matter (DM) (diet C). Fishmeal substitution increased this to 26 (diet FM1) and 34 (diet FM2) g/kg DM. On diets C and FM1, approximately 0.71 of digestible organic matter intake was apparently digested in the rumen, but this was significantly (P less than 0.05) reduced on diet FM2 (0.60). Whilst duodenal flows of non-ammonia N and total amino acids were significantly (P less than 0.01) increased at the highest level of fishmeal inclusion only, the synthesis of microbial N was significantly (P less than 0.001) reduced by fishmeal inclusion, and feed N degradability declined progressively in response to increased fishmeal. Both levels of fishmeal addition caused a significant (P less than 0.05) reduction in the fractional outflow rate of water from the rumen, and on the highest level of fishmeal significant (P less than 0.05) increases in rumen ammonia concentration and rumen propionate molar proportions were observed. The net effect of the highest level of fishmeal substitution was to increase amino acid absorption from the small intestine by 0.47 compared with the control diet (P less than 0.05), but due to an elevated ileal flow of amino acid no such effect was detected at the lowest level of fishmeal substitution. Composition of the absorbed amino acid fraction was relatively unaffected by the treatments imposed, despite large changes in the composition of the duodenal protein. The apparent non-linearity of response to fishmeal substitution is discussed and the amino acid supply findings are compared with the protein retention findings obtained in an earlier study by Gill et al. (1987). By two methods of calculation it was estimated that the amino acid N fraction disappearing from the small intestine was utilized with an efficiency of between 0.51 and 0.53 and no apparent effects due to diet or level of amino acid supply were detected.
在每头装有简单PVC套管的幼龄生长牛中，研究了用两种水平的鱼粉替代（50克/千克（FM1）和150克/千克（FM2））青草青贮对照日粮（C）对瘤胃有机物和氮消化以及小肠氨基酸消失率的影响。套管分别置于网胃-瘤胃背囊、十二指肠近端和回肠末端。青贮料是多年生黑麦草（Lolium perenne）的一次生长草（添加甲酸），干物质（DM）中总氮含量为22克/千克（日粮C）。鱼粉替代后，日粮FM1和FM2的干物质中总氮含量分别增至26克/千克和34克/千克。在日粮C和FM1上，约0.71的可消化有机物摄入量在瘤胃中被消化，但在日粮FM2上这一比例显著（P<0.05）降低（0.60）。仅在鱼粉添加量最高时，十二指肠非氨态氮和总氨基酸流量显著（P<0.01）增加，但鱼粉添加显著（P<0.001）降低了微生物氮的合成，且随着鱼粉添加量增加，饲料氮降解率逐渐下降。两种水平的鱼粉添加均显著（P<0.05）降低了瘤胃水分的分数流出率，鱼粉添加量最高时，瘤胃氨浓度显著（P<0.05）升高，瘤胃丙酸摩尔比例显著增加。与对照日粮相比，鱼粉替代量最高时小肠氨基酸吸收净增加0.47（P<0.05），但在鱼粉替代量最低时，由于回肠氨基酸流量升高，未检测到这种影响。尽管十二指肠蛋白质组成发生了很大变化，但吸收氨基酸部分的组成相对不受处理的影响。讨论了对鱼粉替代反应的明显非线性，并将氨基酸供应结果与Gill等人（1987年）早期研究中获得的蛋白质保留结果进行了比较。通过两种计算方法估计，从小肠消失的氨基酸氮部分的利用率在0.51至0.53之间，未检测到日粮或氨基酸供应水平的明显影响。
