EFFECTS OF INCREASED REARING PERIOD BODY WEIGHTS AND EARLY PHOTOSTIMULATION ON BROILER BREEDER EGG-PRODUCTION

Broiler breeder pullets were subjected to photostimulation (PS) at eit her 14, 17, or 20 wk of age after attaining greater than recommended B W during rearing in order to determine effects on age at onset of lay, egg weight, and egg production. During rearing, feed was consumed ad libitum (AL) or provided in allotments resulting in growth to projecte d BW of 2.8 (heavy, HV) or 2.3 kg (light, LT) at 20 wk. Rearing period feeding and age at PS treatments made up a 3 x 3 factorial arrangemen t. A single restricted feeding program was provided during lay. Althou gh age at first egg in the AL treatment was earlier than in HV and LT treatments, total production by HV and LT birds was greater because pe ak and postpeak production by AL birds were depressed. Relative to PS at 20 wk, PS at 14 and 17 wk advanced age at first egg and increased c umulative production to 30 wk. However, early PS decreased peak produc tion and, therefore, did not affect total production. Mean egg weight and settable egg production (egg weight > 50 g) were increased in HV a nd LT treatments. Egg weight and settable egg production were not affe cted by age at PS. These results indicate that the onset of lay by bro iler breeders can be advanced by early PS and that increased BW facili tates this. However, allowing greater BW during rearing does not compe nsate for reduced early egg weights and results in decreased total pro duction and mean egg weights when feed is provided at recommended leve ls during lay.