EFFECT OF MESENTERIC VEIN INFUSION OF PROPIONATE ON SPLANCHNIC METABOLISM IN PRIMIPAROUS HOLSTEIN COWS

Our objective was to assess the effects of increased propionate supply on gut and liver function in lactating cows. Four multicatheterized, primiparous cows (30.4 +/- .5 kg/d of milk) were fed for ad libitum intake a diet of 50% alfalfa hay and 50% concentrate (20.6 +/- 1.9 kg/d of DM, 226 +/- 21 MJ/d of metabolizable energy, and 611 +/- 56 g/d of N). Each cow received intramesenteric infusions of NaCl (control) or Na-propionate (150 mmol/h of a 2.5 M solution) in a reversal design. After 72 h of infusion, blood flow (by indicator dilution) and net flux (venoarterial differences multiplied by blood flow) were measured across portal-drained viscera and the liver. Energy supply from feed consumed and from infusion was similar between treatments. Energy that was excreted as milk decreased infusion. with propionate Propionate infusion increased arterial concentration of propionate; decreased absorption of acetate, butyrate, and valerate; and decreased hepatic removal of L-lactate, butyrate, valerate, NEFA, and oxygen. Propionate infusion decreased splanchnic release of glucose and increased splanchnic release of acetate and alanine. Net flux of urea, BHBA, insulin, or glucagon was unaffected by treatments. Our data show a link between a greater proportion of energy supplied as propionate and decreased energy excreted as milk. This response was associated with decreased net removal of glucogenic and ketogenic substrates by the liver and increased supply of acetate for use by peripheral tissues.