Response of plasma concentrations of gut peptides to abomasal infusion of casein, starch, or soybean oil in lactating dairy cows.

The effect of nutrient supply to the small intestine on gut peptide secretion in ruminants, and particularly cattle, has not been characterized. The objective of the present study was to determine the effects of abomasal infusion of macronutrients on DMI and plasma concentrations of glucagon-like peptide-1 (GLP1), glucose-dependent insulinotropic polypeptide (GIP), and cholecystokinin (CCK). Four rumen cannulated Holstein cows fed a ration containing (DM basis) 17 % alfalfa haylage, 38 % corn silage and 45 % concentrate were used in a 4 X 4 Latin square design with 2-wk periods. Treatments were 7 d abomasal infusions of water (12 kg/d), soybean oil (500 g/d), starch (1100 g/d), or casein (800 g/d). Hormone concentrations (pmol/L, Table 1) were measured in plasma from jugular vein samples (15/d at 30 min intervals) taken during day 1 and 7 of infusions. Oil infusion decreased DMI (kg/d), but not ME, decreased CCK concentration, and increased GLP1 concentration on day 7. Casein and starch infusion had no effect on DMI, but ME and GIP concentration were increased on day 1 and 7. Casein infusion increased CCK concentration on day 1 and 7. Increased GIP concentration with increased ME may be related to effects of this peptide on adipose synthesis. [ABSTRACT FROM AUTHOR]