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Effects of Age at Photostimulation on Reproductive Efficiency in Three Strains of Broiler Breeders Varying in Breast Yield

N. S. Joseph^*, F. E. Robinson^*, R. A. Renema^* and M. J. Zuidhof

^* Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada, T6G 2P5
Animal Industry Division, Alberta Agriculture, Food and Rural Development, Edmonton, Alberta, Canada, T6H 5T6

Correspondence: F. E. Robinson, E-mail: frank.robinson{at}ualberta.ca

As genetic selection for growth and BW in meat-type stock continues, the age at which photostimulation occurs needs to be increased. This trial studied the relationship between age at photostimulation and egg production and egg weight. Three strains of female broiler breeders varying in potential breast muscle yields were subjected to photostimulation at two ages, 20 versus 23 wk of age. Sexual maturity, egg weight, egg production, and carcass characteristics were assessed.

Hens photostimulated at 23 wk of age weighed more and were older at sexual maturity than hens photostimulated at 20 wk of age. However, the reproductive response to the lighting cue was faster among hens photostimulated at 23 versus 20 wk of age. All three strains responded similarly to both photostimulation treatments. Hens photostimulated at 23 wk of age laid larger eggs throughout the entire production cycle, but the number of small eggs was not reduced. Overall, egg production was not affected by strain or treatment. Breast muscle weight was heavier for hens of an experimental line selected for breast muscle yield (EXP) than for hens selected for high egg production (Classic) or for a slow-feathering strain selected for egg production and moderate breast muscle yield (FSY) hens at 53 wk of age. Delay of photostimulation by 3 wk was effective, as hens on this treatment matured faster and had increased egg weights throughout lay, without experiencing a decrease in egg production.

Key Words: broiler breeder • photostimulation age • egg production parameters • strain of bird