Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 24, 1996
Publication Date: N/A
Technical Abstract: The objective was to determine net portal-drained viscera (PDV) and hepatic flux of nutrients when ewes consuming low-quality forage were supplemented with protein at 0, 24, or 72-h intervals. Six Polled Dorset ewes (37 ñ 4 kg) fitted with hepatic venous, hepatic portal, abdominal aorta, and mesenteric venous catheters were used in a replicated 3 x 3 Latin square design. Ewes were offered brome hay (7.7% CP) ad libitum. Treatments were no soybean meal (SBM; control), SBM fed once every 24 h, or SBM fed once every 72 h. Soybean meal was fed in amounts to provide 80 g/d of CP. Blood flow and net flux measurements were made 3 d of each period so that ewes supplemented on a 72-h interval were sampled the day of, the day after, and 2 d after supplementation. Arterial concentrations of alpha-amino N (AAN) and ammonia N were lower (P < .05) when SBM was fed, whereas arterial concentrations of urea N and oxygen were greater (P < .05). When SBM was fed, net PDV absorption of AAN, ammonia N, and oxygen consumption were greater (P < .05) than in control ewes. Net PDV removal of urea N was not affected (P > .10) by treatment. A SBM day interaction (P < .05) occurred as net PDV absorption of AAN and ammonia N were greater the day after supplementation than the day of or 2-d after in ewes fed SBM on a 72-h interval. Net hepatic removal of AAN, ammonia N, and oxygen, and net hepatic release of urea N were greater (P < .06) in ewes fed SBM compared with control ewes. Interval of protein supplementation may affect the pattern of absorption but does not affect net absorption of nitrogenous compounds.