Role of body weight and food intake after photostimulation on ovarian function at first egg in broiler breeder females

1. The role of body weight during rearing and food allocation after photostimulation on ovarian function in broiler breeder females was examined in two experiments. In experiment 1 birds were fed ad libitum, or to grow to 0.7 or 0.4 of ad libitum-fed body weight at 20 weeks of age. After photostimulation at 16, 19 and 22 weeks respectively they were fed ad libitum, 145 g/d or 115 g/d in a factorial design. The ovary of each bird was examined after it had laid an egg. In experiment 2, restricted birds (0.4 of ad libitum-fed body weight) were fed 195 g/d after laying an egg or ad libitum and a third group were given 125 g/d for 3 to 4 weeks and then fed ad libitum. The ovaries of these birds were examined 6 to 7 weeks after their first egg. 2. Food restriction after photostimulation had little effect on ovarian function in birds fed ad libitum during rearing. These birds had 2 to 3 hierarchies of yellow follicles of similar size. Restricted birds fed ad libitum after photostimulation had a large increase in the numbers of yellow follicles (1.7 to 2.0 hierarchies) compared with birds fed 145 g/d or 115 g/d which had 1.2 to 1.6 hierarchies of yellow follicles. 3. Age at first egg was largely a function of rearing treatment but feeding 115 g/d to the 0.4 treatment birds delayed the onset of lay compared with the other treatments. 4. Ad libitum feeding in restricted birds after the onset of lay resulted in a similar increase in the number of yellow follicles as the response to ad libitum feeding after photostimulation. 5. The prevalence of birds with atretic follicles was relatively high in birds fed ad libitum during rearing and in restricted birds fed ad libitum after photostimulation. 6. Yolk weight increased with age at photostimulation and food restriction decreased yolk weight by about 1 g compared with ad libitum feeding after photostimulation.