Effect of feeding on hepatic and portal blood flow in sheep

Effects of different supplements on splanchnic oxygen consumption and net fluxes of nutrients in sheep consuming bromegrass (Bromus inermis) hay ad libitum

Fifteen sheep (53 kg), with catheters in a hepatic vein, the portal vein and a mesenteric vein and artery, were offered a bromegrass (Bromus inermis) hay (104 g crude protein (CP), 700 g neutral-detergent fibre and 65 g acid-detergent lignin/kg dry matter (DM) ad lib. with different supplements to determine the effects on net flux of oxygen and nutrients across the portal-drained viscera (PDV) and liver. The sheep were unsupplemented (Control) or received 5 g DM/kg body weight (BW) of ground maize (M), 7 g DM/kg BW of soya-bean hulls (H) or 0.73 g DM/kg BW of a mix of feedstuffs high in rumenundegradable protein (P). Apparent digestible energy (DE) intakes were 5.3, 10.4, 10.6 and 6.7 (SE 0.74) MJ/d and apparent digestible CP intakes were 37, 50, 79 and 68 (SE 4.3) g/d for Control, M, H and P treatments respectively. Splanchnic tissue oxygen consumption rates were 0.23, 0.32, 0.30 and 0.27 (SE 0.054) mol/h, and oxidative metabolism accounted for 0.46, 0.31, 0.33 and 0.47 (SE 0.051) of DE intakes for Control, M, H and P treatments respectively. Supplements increased (P < 0.05) release of alpha-amino nitrogen (AAN) by the PDV (4.2, 17.5, 19.6 and 18.1 mmol/h for Control, M, H and P treatments respectively). Splanchnic net flux of AAN was not affected by supplement treatments. Hepatic release of urea-N was increased (P < 0.05) by supplement treatments (27, 40, 46 and 44 mmol/h for Control, M, H and P respectively); the P treatment increased (P < 0.05) and the H treatment tended (P = 0.10) to increase splanchnic release of urea-N (7, 10, 20 and 27 mmol/h for Control, M, H and P treatments respectively). Net flux of glucose across the PDV was -4.6, 1.4, -5.6 and -7.2 (SE 1.65) mmol/h for Control, M, H and P treatments respectively. Hepatic glucose released averaged 23 (SE 2.0) mmol/h and was not affected by treatment. Treatments M and H increased (P < 0.05) PDV release of propionate compared with the Control treatment (4.5, 15.5, 16.8 and 7.7 mmol/h for Control, M, H and P treatments respectively). Release of acetate by the PDV was 43, 97, 118 and 67 (SE 23.9) mmol/h for Control, M, H and P treatments respectively. In summary, different supplements of low-quality grass did not increase the efficiency of N metabolism by splanchnic tissues. Treatment P had little effect on net flux across splanchnic tissues of glucose, L-lactate, beta-hydroxybutyrate and volatile fatty acids (VFA).(ABSTRACT TRUNCATED AT 400 WORDS)