Effects of different dietary protein levels during rearing and different dietary energy levels during lay on behaviour and feather cover in broiler breeder females

• A low protein diet during rearing seems to improve breeder pullet welfare.
• A prolonged eating time due to a higher feed intake results in less stereotypic object pecking.
• Feather cover is negatively affected by a low daily protein intake.
• Effects on behaviour and feather cover are more pronounced during rearing than lay.

An experiment was conducted to determine the effects of different dietary protein levels during rearing and different dietary energy levels during lay on behaviour and feather cover in broiler breeder females. A 2 × 3 × 2 factorial arrangement of treatments was used. A total of 2880 Ross 308 14-day-old broiler breeder pullets were fed between weeks 2 and 22, a high (CPh) or low (CPl) crude protein (CP) diet. Between weeks 22 and 45, the breeders were fed either a high, standard, or low energy diet (3000, MEh1; 2800, MEs1; 2600, MEl1, kcal/kg AMEn (apparent metabolisable energy, corrected for nitrogen), respectively). Between weeks 45 and 60, the breeders were fed a standard or high energy diet (2800, MEs2; 3000, MEh2, kcal/kg AMEn, respectively). During rearing, CPl pullets received 12.1% more feed, resulting in a 137% increased eating time and 47% decreased eating rate. This increased feeding, sitting, and comfort behaviour while standing, walking, foraging, stereotypic object pecking, and bird pecking were reduced. Feather cover was poorer when pullets were fed a low protein diet during rearing, but this effect was not present during lay. A 7.6% lower feed intake for the MEh1 birds resulted in a 21% decreased eating time and 19% increased eating rate compared with the MEs1 birds. Birds on the MEh1 diet spent less time feeding and more time sitting, comfort, and stereotypic object pecking behaviour compared with the MEs1 birds. Birds fed the MEh1 diet showed a poorer feather cover during the entire lay compared with the MEs1 birds. A 7.7% higher feed intake for the MEl1 birds resulted in a 31% increased eating time and 18% decreased eating rate compared with the MEs1 birds. MEl1 birds spent more time feeding and less time foraging, comfort, and stereotypic object pecking compared with the MEs1 birds. No effect on feather cover was found for the MEl1 compared with the MEs1 birds. The MEh2 birds received 8.8% less feed resulted in a 16% decreased eating time and 9% increased eating rate. The lower feed intake resulted in less time spent feeding and standing, and more time spent foraging and comfort behaviours. Feather cover was not affected by dietary energy level during the second phase of lay. In conclusion, feeding broiler breeders a higher amount of feed due to a higher energy-to-protein ratio resulted in an increased eating time and less stereotypic object pecking behaviour what is an indication of reduced hunger and frustration. This was much more expressed during rearing than lay. However, a low daily protein intake during rearing and first phase of lay can lead to a poorer feather cover.