Effects of propionate infusion and dietary energy on dry matter intake in sheep

Four nonlactating, nonpregnant, mature ewes equipped with multiple venous and arterial catheters were used to evaluate the influence of propionate as a satiety signal in ruminants. Our experiment was a 4 x 4 Latin square with portal infusion (physiological saline [Sa] or sodium propionate [Pr]) and DE intake (Lo, 63% of maintenance requirement, or Hi, 200% of maintenance requirement) as factors. One 240-min infusion of Pr (1 mmol/min) or Sa into the portal vein began at approximately 0800 on d 8 of each 8-d period. Feed intake was measured and hepatic blood was sampled every 30 min during infusion. Intake of DM and digestible energy (DEI) during infusion were not affected by infusion or diet and were most rapid at 30 min postfeeding. Average 30-min DMI and DEI were 539 g and 1,484 kcal, respectively, at 240 min. Cumulative DMI and DEI were unaffected by infusion but tended to be greater with Lo. After 30 min, animals tended to consume Lo at a greater rate than Hi, suggesting that satiety was delayed. Insulin concentration was increased (P less than .02) when animals consumed Hi (36.1 mU/liter) vs Lo (16.8 mU/liter) and was elevated (P less than .01) at 30 and 60 min postfeeding when animals were infused with Pr. Plasma acetate tended to be reduced with Pr infusion. Plasma Pr tended to increase with Pr infusion, especially when sheep were fed Lo. Satiety, DMI, and DEI were not affected by Pr infusion in this study.