The metabolisable energy (ME) of the diet of laying hens at an ambient temperature (Ta) of 20 degrees C was abruptly changed from 10.9 MJ/kg to 12.9 MJ/kg, or vice versa. Food intake during the next 14 d was significantly reduced by the low ME diet and was increased by the high ME diet, that is, the expected compensatory changes in food intake did not occur. Laying hens given the same change of diet as above but kept at 32 degrees C did not show any change in food intake within 14 d. Thus ME intake increased with the high ME diet and decreased with the low ME diet. Daily doses of 10 ml
maize oil/kg
body weight given directly into the crop of laying hens at a Ta of 20 degrees C, resulted in an immediate, significant, reduction of food intake such that total ME intake remained the same as with normal feeding. Daily doses of 3 ml
maize oil/kg, given as before, resulted in an immediate, significant, reduction in food intake at a Ta of 20 degrees C but at a Ta of 32 degrees C food intake remained unchanged; consequently daily ME intake increased. Loading the crop with
glucose or
sucrose, at Ta 20 degrees C, in quantities which provided a similar ME as 3 ml
maize oil/kg, reduced food intake but the adjustment was less precise and daily ME intake increased. Loading with
glycerol or
protein hydrolysate decreased both food and ME intake. Crop loads of
starch were as effective as
maize oil in bringing about a significant and compensatory reduction of food intake. Similar volumes of water or
liquid paraffin placed in the crop did not affect food or ME intake. A similar weight or
cellulose placed in the crop reduced food and ME intake.