title: Photorefractoriness in turkey breeder hens is affected by age and season.
abstract: Experiments were conducted to determine if the incidence or temporal characteristics of photorefractoriness (PR) in turkey hens were influenced by age or season. Age effects on PR were determined by comparing characteristics of PR in the same hens through two consecutive lay periods. Seasonal influences on PR were evaluated by comparing characteristics of PR in hens photostimulated into lay at different seasons of the year. The onset of PR was evaluated by the spontaneous cessation of lay. Data were collected from daily egg production records for time to onset of PR, time to spontaneous termination of PR, and time required for the transition from photosensitive to the PR state. Percentage incidence, repeatability between consecutive cycles, and persistence (duration) of PR were calculated. Age did not influence the mean time to onset of PR following photostimulation but did affect percentage incidence. All second-year hens (recycled) expressed PR, whereas 89% of the first-year hens did so. Time to onset of PR was not correlated between first- and second-year (recycled) hens. Most, but not all, first-year (84.4%) and recycled (92%) hens were transiently PR and spontaneously terminated PR after 20 to 21 wk of unchanged photoperiod. Hens photostimulated in the winter (December) had delayed mean time to onset of PR from that observed with hens photostimulated in spring (May) by about 7.7 wk. Percentage incidence of PR and duration of PR were similar in both seasons of the year. It was concluded that age and season could affect PR.
authors.affiliation: Department of Poultry Science, College of Agriculture and Life Sciences, North Carolina State University, Raleigh 27695-7608, USA. tom_siopes@ncsu.edu
authors.forename: T D
authors.initials: TD
authors.lastname: Siopes
mesh_terms: D000367:Age Factors; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D015994:Incidence; D008027:Light; D010058:Oviposition / Q000502:physiology*; D010775:Photic Stimulation; D017440:Photoperiod; D012621:Seasons; D013997:Time Factors; D014422:Turkeys / Q000502:physiology*