Reynolds C K, Tyrrell H F, Reynolds P J
U.S. Department of Agriculture, Livestock and Poultry Sciences Institute, Beltsville, MD 20705.
J Nutr. 1991 Jul;121(7):1004-15. doi: 10.1093/jn/121.7.1004.
Effects of diet forage-to-concentrate ratio and intake on metabolism of nutrients by portal-drained viscera (PDV), liver and kidneys were measured in seven growing beef heifers. Isonitrogenous pelleted diets containing approximately 75% alfalfa or 75% concentrate were fed every 2 h at two metabolizable energy intakes. Greater intake increased net PDV removal of glucose and urea nitrogen and net PDV release of NH3N, alpha-amino nitrogen (AAN), alanine and lactate. Lower net PDV release of NH3N, liver removal of NH3N and AAN and liver release of urea nitrogen accompanied lower N intake and digestion in heifers fed the 75% concentrate vs. the 75% alfalfa diet. Lower net PDV glucose removal resulted in greater total splanchnic glucose release when heifers were fed the 75% concentrate vs. the 75% alfalfa diet. In addition, net PDV, liver and total splanchnic release of beta-hydroxybutyrate (BOHB) were lower when heifers were fed the 75% concentrate vs. the 75% alfalfa diet. Greater tissue energy retention in heifers fed the 75% concentrate vs. the 75% alfalfa diet at equal metabolizable energy intake accompanied differences in net PDV metabolism of glucose, NH3N and BOHB and liver metabolism of nitrogenous compounds, BOHB and lactate.
在七头生长中的肉用小母牛中，测定了日粮粗饲料与精饲料比例及采食量对门静脉引流内脏（PDV）、肝脏和肾脏养分代谢的影响。以两种代谢能采食量，每2小时饲喂一次含大约75%苜蓿或75%精料的等氮颗粒日粮。采食量增加会使PDV对葡萄糖和尿素氮的净清除量以及PDV对NH₃N、α-氨基氮（AAN）、丙氨酸和乳酸的净释放量增加。与饲喂75%苜蓿日粮相比，饲喂75%精料日粮的小母牛，其较低的N采食量和消化率伴随着较低的PDV对NH₃N的净释放量、肝脏对NH₃N和AAN的清除量以及肝脏对尿素氮的释放量。当小母牛饲喂75%精料日粮而非75%苜蓿日粮时，较低的PDV对葡萄糖的净清除量导致内脏总葡萄糖释放量增加。此外，与饲喂75%苜蓿日粮相比，饲喂75%精料日粮时，PDV、肝脏和内脏对β-羟基丁酸（BOHB）的净释放量更低。在等代谢能采食量下，饲喂75%精料日粮的小母牛比饲喂75%苜蓿日粮的小母牛具有更高的组织能量保留，这伴随着PDV对葡萄糖、NH₃N和BOHB的净代谢以及肝脏对含氮化合物、BOHB和乳酸的代谢差异。
