Nutrients intake of grazing sheep based on net flux of nitrogen and oxygen by splanchnic tissues

通过两年多的三个试验，研究放牧绵羊的能量摄入和氮(N)代谢，以及门静脉引流脏器(PDV)和肝脏耗氧量。门静脉、肝静脉、肠系膜静脉和腹主动脉长期留置导尿管的病人在限制进食的住房下使用(实验。1和2)和随机性摄取放牧(实验3)条件Exp.1.绵羊饲喂含粗饲料(70)和精料(30)四个水平的饲料，维持能(M)为0.5~1.76倍。绵羊的消化能、氮的摄入量和氮的存留率随着饲喂水平的提高呈线性增加。PDV对氨氮的吸收也呈线性增加，而α-氨基氮的吸收从0.5M的零开始呈二次曲线增加。2.绵羊饲喂饲料(1.0M)加大麦补充剂(0~1.0M)。可消化能和氮摄入量呈线性增加，但氮滞留量与补充量呈二次曲线关系。α-氨基氮的PDV释放量随添加水平的增加而线性增加，但由于肝脏摄取量的增加，内脏组织(TSP)的a-氨基氮释放量几乎不变。增加补充量可线性提高PDV对尿素氮的去除，但不影响肝脏尿素氮的合成和PDVExp对氨氮的吸收。他说：5月和6月期间，人们在牧场上放牧绵羊。TSP释放的α-氨基氮随大麦的增加而增加，6月份较5月份有所减少。可消化能量摄入量，通过试验中PDV耗氧量和能量摄入量之间的线性回归来估计。1和2，在6月份较大，不受大麦补充的影响

The objectives were to investigate energy intake and nitrogen (N) metabolism of grazing sheep with net flux of N and oxygen consumption by the portal drained viscera (PDV) and liver through three experiments over two years. Wethers with chronic indwelling catheter in the portal, hepatic and mesenteric veins and the abdominal aorta were used under housing with restricted feeding (Exp. 1 and 2) and grazing with adlibitum intake (Exp. 3) conditionsExp. 1 : The sheep were fed a diet consisting of forage (70) and concentrate (30) at four levels, 0.5 to 1.76 times maintenance energy (M). Digestible energy and N intakes and N retention of sheep linearly increased with the feeding level. Ammonia N absorption by PDV also increased linearly, while α-amino N absorption, starting from null at 0.5M, increased quadraticallyExp. 2 : The sheep were fed forage (1.0M) plus four amounts of barley supplement (0 to 1.0M). Digestible energy and N intakes increased linearly, but N retention quadratically responded to the supplement level. The PDV release of α-amino N increased linearly with the supplement level, although the a -amino N release by the total splanchnic tissues (TSP) was almost constant due to the increase in the liver uptake. The increased supplement linearly increased the remove of urea N by PDV, but did not affect urea N synthesis by the liver and ammonia N absorption by PDVExp. 3 : The sheep were grazed on a pasture during May and June. The α-amino N release by TSP increased with barley supplement, and was less in June compared with May. Digestible energy intake, estimated with a linear regression between the PDV oxygen consumption and energy intake in Exp. 1 and 2, was greater in June, and not affected by barley supplement