The effect of twenty-eight-hour ahemeral day lengths on carcass and reproductive characteristics of broiler breeder hens late in lay

Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada.

The effect of increasing the day length from 24 to 28 h on the reproductive and carcass characteristics of old broiler breeder hens was examined. A total of 128 birds aged 47 wk of age from three different strains; Classic, Experimental (EXP), and Feather Sexable Yield (FSY) were used. Selection was based on target BW and egg production rates; birds were housed in light-tight environment chamber facilities. Birds were feed restricted, and feed was allocated according to actual weekly BW relative to target BW. At 55 wk of age 125 broiler breeders were killed and dissected, and carcass and reproductive traits were examined. Overall, ahemeral day length negatively affected carcass and reproductive parameters. No significant differences were found for BW, yolk, albumen and shell weights, normal and atretic ovarian follicles, and breast, fat pad, and liver weights. Significantly lower production rates, higher amounts of defective eggs, lower oviduct and ovary weights, lower F1 follicle weight, poorer eggshell quality, and higher egg weights were found. Subsequently, broiler breeder hens increased egg weight at the expense of egg production when subjected to an ahemeral day length. It is not recommended that day length be increased this late in production because it results in reduced egg productivity.