Effects of pre-feeding on food-approach latency and food consumption speed in food deprived rats.

Deprived rats were trained to receive a major portion of their daily food ration in meal segments of five 45 mg food pellets, presented for 36 sec each at 72 sec intervals. Latency to make oral contact with first pellets did not change over 18 meal segments, while the time to complete the eating of meal segments increased progressively. Pre-feeding with 45 or 90 pellets had little effect on latencies except in the last few trials in the 90-pellet condition. Pre-feeding had a marked effect on time to complete segments, increasing it in proportion to the number of pellets consumed. Thus satiation caused a progressive change in speed of eating, while it caused an all-or-none change in initiation of eating. That is, animals responded to new food pellets with normal latency up to the point when they stopped responding completely. With repeated testing the effects of prefeeding on both speed and latency measures was reduced; the animals ate more steadily, and came to eat every pellet, as familiarity with the situation increased.