Effects of lighting program during the growing period and dietary fat during the laying period on broiler breeder...

In two experiments, broiler breeders were grown in either of two lighting regimens, fed diets without added fat, and then fed diets with or without 5% added poultry fat during the subsequent laying period. In Experiment 1 half the birds were subjected to decreasing daylength using daylight (800 lx) and half were subjected to 9 h of incandescent light (20 lx) to 20 wk of age. In Experiment 2 the lighting regimen was either an 8-h photoperiod supplied by daylight (800 lx) or an 8-h photoperiod supplied by incandescent light (20 lx) to 20 wk of age. Added dietary fat produced significantly higher egg weight (Experiments 1 and 2), egg production (Experiment 2), and significantly lower fertility and hatchability of fertile eggs (Experiments 1 and 2). Short photoperiods (8 or 9 h) provided by incandescent light produced significantly higher fertility (Experiments 1 and 2) and hatchability of fertile eggs (Experiment 2), and significantly lower egg specific gravity, shell percentage (Experiment 1), egg weight, and eggshell weight (Experiment 2). Effects on fertility may be related to higher female body weight during lay due to daylight rearing or added fat, or relative changes in light intensity at photostimulation.