Splanchnic metabolism of nutrients and hormones in steers fed alfalfa under conditions of increased absorption of ammonia and L-arginine supply across the portal-drained viscera.
Effects of increased ammonia and/or arginine absorption on net splanchnic (portal-drained viscera [PDV] plus liver) metabolism of nonnitrogenous nutrients and hormones in cattle were examined. Six Hereford x Angus steers (501 +/- 1 kg BW) prepared with vascular catheters for measurements of net flux across the splanchnic bed were fed a 75% alfalfa:25% (as-fed basis) corn and soybean meal diet (0.523 MJ of ME/[kg BW(0.75).d]) every 2 h without (27.0 g of N/kg of DM) and with 20 g of urea/kg of DM (35.7 g of N/kg of DM) in a split-plot design. Net flux measurements were made immediately before and after a 72-h mesenteric vein infusion of L-arginine (15 mmol/h). There were no treatment effects on PDV or hepatic O2 consumption. Dietary urea had no effect on splanchnic metabolism of glucose or L-lactate, but arginine infusion decreased net hepatic removal of L-lactate when urea was fed (P < 0.01). Net PDV appearance of n-butyrate was increased by arginine infusion (P < 0.07), and both dietary urea (P < 0.09) and arginine infusion (P < 0.05) increased net hepatic removal of n-butyrate. Dietary urea also increased total splanchnic acetate output (P < 0.06), tended to increase arterial glucagon concentration (P < 0.11), and decreased arterial ST concentration (P < 0.03). Arginine infusion increased arterial concentration (P < 0.07) and net PDV release (P < 0.10) and tended to increase hepatic removal (P < 0.11) of insulin, as well as arterial concentration (P < 0.01) and total splanchnic output (P < 0.01) of glucagon. Despite changes in splanchnic N metabolism, increased ammonia and arginine absorption had little measurable effect on splanchnic metabolism of glucose and other nonnitrogenous components of splanchnic energy metabolism.
Maltby
S A
SA
USDA, ARS, Beltsville, MD 20705, USA.
Reynolds
C K
CK
Lomax
M A
MA
Beever
D E
DE
D020155:3-Hydroxybutyric Acid / Q000097:blood; D000042:Absorption; D000641:Ammonia / Q000493:pharmacokinetics*; D000818:Animals; D001120:Arginine / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D001786:Blood Glucose / Q000032:analysis; D002417:Cattle / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000097:blood; D005934:Glucagon / Q000378:metabolism; D007262:Infusions, Intravenous / Q000662:veterinary; D007328:Insulin / Q000378:metabolism; D008099:Liver / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010100:Oxygen / Q000097:blood; D011169:Portal Vein; D011897:Random Allocation; D012039:Regional Blood Flow / Q000187:drug effects; D014508:Urea / Q000008:administration & dosage / Q000494:pharmacology*; D014781:Viscera / Q000378:metabolism*
D001786:Blood Glucose; D005232:Fatty Acids, Volatile; D007328:Insulin; D000641:Ammonia; D014508:Urea; D005934:Glucagon; D001120:Arginine; D010100:Oxygen; D020155:3-Hydroxybutyric Acid