Stereotyped pecking after feeding by restricted-fed fowls is influenced by meal size

Growing broiler breeder chickens, fed routinely according to a programme of chronic food restriction, typically show increased pacing before feeding time and increased drinking and pecking at non-food objects afterwards. Expression of this behaviour is often stereotyped in form. In two experiments at 8 and 14 weeks of age, they were caged individually, provided with two meals per day at 0900 and 1600 h, and tested with 0900 h meals that differed in either size (10, 25, 40 g) bur not food form (pellets), or food form (pellets, mash, influencing meal duration) but not size (15 g). Measurements of behaviour were made from video recordings between 0915 (when all feeding had ceased) and 1600 h. As meal size increased, so did the proportion of time spent in stereotyped object pecking after feeding, while time spent standing (only) decreased; there were no other significant effects of either meal size or food form on post-feeding behaviour. The observed effect of meal size on object pecking may be a consequence of the weight of food eaten per se, rather than the time taken to eat it; this conclusion is tentative because results of the food form comparison are not unambiguous. Paradoxically, whereas expression of abnormal behaviour in restricted-fed animals is known to be correlated negatively with total daily food intake, it appears to be correlated positively with meal size within a given level of restriction. (C) 1999 Elsevier Science B.V. All rights reserved.