Effect of strain, feed allocation program, and age at photostimulation on reproductive development and carcass characteristics of broiler breeder hens

A study was conducted with broiler breeder pullets to investigate the effects of strain, age at photostimulation (PS), and release from feed restriction at PS on age, BW, ovarian morphology, and carcass characteristics at sexual maturity (point of initiation of lay). Sixty birds of each of 4 strains were used. The 4 types represented a classic strain (A), 2 high-yield strains (B, C), and a roaster strain (D). Photostimulation (8L:16D to 14L:10D) was applied at 2 different ages (21 and 24 wk) to 30 birds of each strain type. Within each of the PS periods, 15 birds of each strain were fed ad libitum (F), and the remaining 15 were feed-restricted (R) following a common feeding schedule. On the day that each bird had its first oviposition, its feed was withdrawn. It was euthanized the following morning by cervical dislocation and organs were collected. Of the 3 main effects, feeding program had the greatest effect on all the parameters measured. Within the 21-wk PS treatment group, R birds reached onset of sexual maturity later than F birds (50.2 +/- 1.64 vs. 36.6 +/- 1.01 d, respectively). There were no differences in the age at sexual maturity between R and F birds for the 24-wk PS treatment (28.9 +/- 0.95 vs. 26.9 +/- 0.85 for R and F, respectively). These results suggest that by 24 wk, all strains had reached a threshold BW and responded uniformly to PS regardless of feeding program. Feed restriction reduced the number of large yellow follicles (LYF) (diameter >10 mm) (8.43 +/- 0.23 vs. 9.65 +/- 0.33 for R and F birds, respectively). Follicle number was not different between birds photostimulated at 21 or 24 wk (9.6 +/- 0.33 vs. 8.45 +/- 0.23, respectively). Feed restriction affects sexual development that can be modulated by the PS program.