Effects of rumen energy supply timing on feed intake control in lactating dairy cows

The aim of this trial was to demonstrate the mechanisms and dynamics of signals triggered by digestion in the short-term control of feed intake. Large nylon bags containing rolled wheat were placed into the rumens of four fistulated cows-either prior to feed distribution or during a feeding period-and left for 4 h. To account for bag volume and its effects, bags full of indigestible sawdust were used as a control. The four treatments were compared according to a Latin square design with three replications. Regardless of their contents, when bags were present during the experimental feeding period, intake decreased by 1.2 kg of dry matter through a filling effect. Wheat in the bags had no specific effect on intake during the experimental intake period. Conversely, on the day after the experiment, the presence of wheat during feeding caused a 4.2-kg dry matter decrease in intake compared with the sawdust control. This trial indicated that the nutritional feedback signaling effect on intake control during meals is delayed, contrary to that of rumen fill. Moreover, the delayed effect on intake is only observed when nutrient cues are synchronous with meals, and, consequently, could be the result of experience.