1. A 3 x 2 factorial experiment was conducted with three diets and two lines of broiler breeder females to evaluate the contribution of low-energy rations for improving the welfare of feed-restricted birds during rearing. Experimental diets were fed from 6 to 16 weeks of age and were created by diluting a conventional grower ( Control) ration containing 11.0MJ ME/kg with 200 ( 8.8MJ ME/kg) or 400 ( 6.6MJ ME/kg) g oat hulls/kg using Optimoist to facilitate the pelleting process. Welfare was assessed by changes in behaviour and physiological variables at 8, 12 and 16 weeks of age. Birds were fed restricted quantities of feed to meet recommended body weight targets.
2. There was a decrease in the proportion of observations of drinking and an increase of preening in birds fed on the two experimental diets compared with the control. There was a linear decrease in litter moisture and the number of litter changes with increasing diet dilution, and water intake at 12 weeks was higher in the control than in the two experimental diets. There were no changes in physiological indexes of welfare ( heterophil-lymphocyte ratio, plasma corticosterone and antibody responses) associated with the dietary treatments.
3. There were no important differences in the growth, behaviour or physiological responses to dietary treatment between the two lines of broiler breeders. Changes with age were similar to those reported in other experiments.
4. It was concluded that low-energy pelleted diets would improve litter conditions but not improve indexes of welfare in feed-restricted broiler breeders.