Volatile fatty acids and the role of the large intestine in the control of feed intake in ponies.

The roles of volatile fatty acids (VFA) and of the large intestine in the control of feeding in ponies were investigated. Ponies with cecal fistulas were adapted to ad libitum access to pelleted feed. Treatment solutions were given as a bolus 15 min before the animals were allowed free access to feed after a 4-h fast. Each dose of VFA solution was tested in a crossover design with a water control. When the ponies were permitted to eat after the treatments, the latency to eat, first meal size, and duration and first intermeal interval were recorded. Feed intakes were measured at 3 and 18 h after the treatments were given. Intracecal infusions of .4 mmol propionate (Prop)/kg body weight (BW) increased (P less than .05) total feed intake 7.5% relative to control values. Higher doses of Prop (.75 mmol/kg BW) and acetate (1.00 and 1.25 mmol/kg BW) reduced (P less than .05) feed intake by prolonging the first intermeal interval 143% (Prop) and 71 to 74% (acetate), although 24-h intakes did not differ from controls. The highest dose of Prop tested (1.00 mmol/kg BW) reduced first meal size 22% (P less than .01) without affecting subsequent feeding behaviors. The results indicate that changes in cecal VFA concentration can generate cues that may contribute to the control of meal size and frequency in ponies.