Quantification of reproductive changes and nutrient requirements of broiler breeder pullets at sexual maturity.

1. 480 Broiler breeder pullets, kept in individual cages, were subjected to different rates of increase in food allocation during the period 18 to 30 weeks of age. From 80 g food/bird d at the start of the experiment, the 5 treatments comprised linear weekly increments in food allocation to reach a maximum of 150 g/bird d at 21, 23, 25, 27 or 29 weeks of age respectively. 2. Body weight, liver weight, fat pad weight and alimentary tract weight were influenced by the rate of increment in food allocation. 3. Rate of development of the oviduct and the ovary was not influenced by these treatments. 4. Although the amount of fat and protein contained in the liver increased most rapidly on the treatments where 150 g/bird d was attained first, by 25 weeks of age there were no meaningful differences in these two variables between treatments. It is unlikely, therefore, that a high protein intake during this period would allow sufficient protein or energy to be stored in the liver to sustain a higher egg output later in the laying period. 5. It is concluded that the amount of protein required by a broiler breeder pullet for maintenance and for growth during the pre-laying period is about 10 g/bird d.