Guerino F, Huntington G B, Erdman R A
Dept. of Anim. Sci., University of Maryland, College Park 20742.
J Anim Sci. 1991 Jan;69(1):387-95. doi: 10.2527/1991.691387x.
Changes in net portal and hepatic nutrient flux and oxygen consumption in response to 3-d abomasal casein infusions were studied in seven multicatheterized beef steers. Steers were fed 4.3 kg DM/d of a high-concentrate diet in 12 equal meals. Blood flow (para-aminohippurate dilution) and net flux (venoarterial concentration difference x blood flow) across portal-drained viscera (PDV) and hepatic tissues were measured on d 3 of the abomasal infusions. In two experiments, the response to 300 (300C) and 150 (150C) g casein/d were compared, respectively, to a control water infusion. The 300C increased (P less than .05) arterial blood concentrations of alpha-amino N (AAN), urea N and ammonia; 150C increased (P less than .05) arterial urea N. Urinary urea N excretion was increased (P less than .01) by 300C and 150C. Although 300C increased net PDV release of AAN (P less than .07) and alanine (P less than .10), there was no net change in total splanchnic (TSP) flux due to an increased net hepatic uptake of AAN (P less than .01) and alanine (P less than .05). Net PDV glucose flux was decreased (P less than .05) by 300C, but net hepatic glucose flux was not affected by either level of casein. The 150C increased TSP oxygen consumption (P less than .05) and hepatic oxygen extraction (P less than .10). Approximately 26 and 30% of the casein N infused abomasally appeared in the portal blood as AAN for 150C and 300C, respectively. The sum of net PDV ammonia and AAN fluxes accounted for 47 and 88% of the N infused for 150C and 300C, respectively. These data emphasize the importance of intestinal and liver tissues in regulating the flux of nitrogenous compounds absorbed from the diet.
在7头多导管安装的肉牛中，研究了真胃灌注酪蛋白3天对门静脉和肝脏营养物质通量以及氧消耗的影响。肉牛以12等份的方式，每天饲喂4.3千克干物质的高浓缩日粮。在真胃灌注的第3天，测量门静脉引流内脏（PDV）和肝脏组织的血流量（对氨基马尿酸稀释法）和净通量（动静脉浓度差×血流量）。在两个实验中，分别将300（300C）和150（150C）克/天酪蛋白的反应与对照水灌注进行比较。300C组使动脉血中α-氨基氮（AAN）、尿素氮和氨的浓度升高（P<0.05）；150C组使动脉尿素氮升高（P<0.05）。300C组和150C组使尿尿素氮排泄增加（P<0.01）。虽然300C组使PDV的AAN净释放量增加（P<0.07）和丙氨酸净释放量增加（P<0.10），但由于肝脏对AAN（P<0.01）和丙氨酸（P<0.05）的净摄取增加，内脏总通量（TSP）没有净变化。300C组使PDV葡萄糖净通量降低（P<0.05），但肝脏葡萄糖净通量不受任何酪蛋白水平的影响。150C组使TSP氧消耗增加（P<0.05）和肝脏氧摄取增加（P<0.10）。真胃灌注的酪蛋白氮中，分别约有26%和30%以AAN的形式出现在门静脉血中，对应150C组和300C组。PDV氨和AAN净通量之和分别占150C组和300C组灌注氮的47%和88%。这些数据强调了肠道和肝脏组织在调节从日粮中吸收的含氮化合物通量方面的重要性。
