The effect of abrupt changes in the concentration and frequency of feeding milk-substitute diets on the voluntary food intake of calves.

1. To examine the relations between short- and long-term regulation of food intake in calves given milk-substitute diets, abrupt changes were made in the dry matter (DM) concentration of the diet (Expt 1) and in the frequency of feeding (Expts 2 and 3). 2. When calves, fed once daily, had the DM concentration of their diet changed, they drank the same volume of milk on the 1st day they received the new diet as they had on the previous days; so the DM intakes changed in proportion to the change in milk DM concentration. Over the subsequent 6 d, milk intake progressively increased when milk DM concentration was reduced. When the DM concentration of milk was increased the volume of milk drunk was reduced to a minimum value 2-3 d after the change in diet and increased thereafter. The size of the changes was dependent on the initial and changed DM concentrations of the milk. 3. In calves receiving milk-substitute diets containing 80-260 g DM/kg, milk intakes were reduced by up to 30% on the 1st day that calves were fed once daily instead of twice daily. Over the subsequent 13 d of once-daily feeding, milk intakes increased, particularly for calves given diets of low DM concentration. 4. Feeding the calves once daily reduced the digestibility of DM in Expt 2 but not the digestibility of crude protein (nitrogen x 6.25) and fat; diets containing lower concentrations of DM were particularly affected.(ABSTRACT TRUNCATED AT 250 WORDS)