Effects of abomasal infusion of long-chain fatty acids on splanchnic metabolism of pancreatic and gut hormones in lactating dairy cows

Pancreatic and gut peptide hormones are potential mediators of the reduction in dry matter intake (DMI) often observed in lactating dairy cows fed supplemental fat. We investigated the effects of 7-d abomasal infusions of a rapeseed and sunflower oil mixture providing mostly unsaturated long-chain fatty acids (LCFA) on arterial concentration and splanchnic (portal-drained viscera [PDV] and liver) metabolism of insulin, pancreatic (PAN) and gut (GUT) glucagon, glucagon-like peptide-1 (7-36) amide (GLP-1), and cholecystokinin (CCK) in six cows at 55 (ELAC) and 111 (MLAC) d postpartum Plasma flow for the PDV and liver were greater in ELAC and increased by oil infusion. Arterial concentrations of insulin and PAN were greater in MLAC, whereas arterial concentrations of GLP-1 and CCK were greater in ELAC. Abomasal oil infusion increased arterial concentration of GUT and GLP-1 but decreased arterial insulin concentration. These differences in peripheral hormone concentration were due largely to changes in their net PDV release and (or) liver removal. In addition, net liver removal of PAN was increased by oil infusion. There was no effect of oil infusion on splanchnic metabolism or arterial concentration of CCK. Lower concentrations of CCK in MLAC were attributable to net liver removal, emphasizing the importance of liver metabolism in determining peripheral concentrations of gut and pancreatic peptide hormones. Results of this study suggest a role for products of proglucagon processing (PAN, GUT, and GLP-1) as mediators of the reduction in DMI caused by postruminal supply of LCFA.