Visceral oxygen consumption during chronic feed restriction and realimentation in sheep

The objectives of this study were twofold: first, to estimate the time required to reach equilibrium in splanchnic tissue oxygen (O2) consumption rates after a feed restriction that maintained BW; and second, to estimate the time following a subsequent realimentation required to reach equilibrium. Catheters were placed in a cranial mesenteric vein, the portal vein, a branch of the hepatic vein, and the abdominal aorta of six wethers. Wethers were allowed to eat ad libitum 2 h/d. At 49.9 +/- 2.7 kg two wethers were assigned to the high group, which continued to receive the 2 h/d ad libitum meal. Four wethers were assigned to the low group for 80 d and were restricted to 70% of the average meal each consumed during the week before restriction. Hepatic and portal-drained viscera (PDV) O2 consumption rates were determined the day before restriction (day 0) and on d 10, 24, 38, 52, 66, and 80 of restriction. After d 80 of restriction, wethers assigned to the low group were fed the 2 h/d ad libitum meal, and hepatic and PDV O2 consumption rates were determined on d 7, 14, 28, and 42 of realimentation. At 80 d of restriction, PDV and hepatic O2 consumptions were 60 and 65%, respectively, of the d-0 rate. Hepatic tissue required 21 d and PDV required 29 d to be within 5% of the new steady-state O2 consumption rates after restriction.