Photorefractoriness and sexual response in aging partridge kept under constant long- and short-day photoperiods

The duration of post-juvenile refractoriness was studied in Red-legged partridge kept under a long constant 16-hr photoperiod from hatch to 55 months of age. A second group of partridge was kept under a short constant 8-hr photoperiod from hatch to 38 months of age. Body weight was measured bimonthly, and daily egg production kept on birds reaching sexual maturity. Eighty one percent of all birds were alive at 36 months of age. Birds kept under a constant 16-hr photoperiod were generally heavier at all ages than comparable birds kept under 8-hr photoperiods. Refractoriness was terminated in 38% of the hens kept continuously under a 16-hr day. The first hen laid at 475 days of age. Median age at first egg for other sexually mature birds was 968 days. Forty percent of all birds kept under a constant 8-hr day laid at a median age of 339 days. It was concluded that post-juvenile refractoriness can be interrputed in some partridge without previous exposure to a short-day photoperiod. It is likely that uncontrolled resident temperature fluctuations and other seasonal effects may serve as preconditioners to lay.