Abstract
ABSTRACT Often, in pet birds, any stimulus to lay eggs is unwanted in order to reduce reproductive diseases and disorders. The objectives of this study were: to determine the time necessary to promote ovary involution after an eight hour photoperiod using laying Japanese quails (Coturnix coturnix japonica); to connect the ovarian radiographic measurements with egg production; and to compare these measurements with direct ovary data obtained at necropsy. Birds were separated into three groups: 12h/24d (control group - 12h photoperiod for 24 days), 8h/24d and 8h/36d (8h photoperiod for 24 and 36 days). After euthanasia, all cadavers were x-rayed to measure ovary length and height. Birds were necropsied to measure ovarian length and weight. Results: radiographic ovary length demonstrated strong and positive correlation (r=0.96) with direct ovary length of all three groups; laying quails showed higher ovary height (p=0.025) and length (p=0.009) than non-laying quails; eight hours of artificial light per day promotes ovary length (p=0.025) and weight (p=0.009) reduction. Conclusions: radiography can estimate the ovary measure and indicate posture; an eight hour photoperiod of 24 days is not enough to promote ovarian regression, while the use of reduced photoperiod for 36 days promotes significant ovary involution.
Highlights
Most bird species have periodic reproductive cycles and light availability is the external stimulus that most affects this cycle (Olanrewaju et al, 2006; Pereira, 2014)
Artificial lighting may interfere with the normal annual light cycle and result in inappropriate hormonal cycling, which may lead to excessive egg laying and other problems (Bowles, 2002)
There are reports that say the decrease of the photoperiod can cease egg production (Romagnano, 1996; Pye et al, 2001), there is no information about the necessary time of reduced photoperiod and the light conditions to promote ovary involution and to stop egg production (Bowles, 2002; Rosen, 2012)
Summary
Most bird species have periodic reproductive cycles and light availability is the external stimulus that most affects this cycle (Olanrewaju et al, 2006; Pereira, 2014). Artificial lighting may interfere with the normal annual light cycle and result in inappropriate hormonal cycling, which may lead to excessive egg laying and other problems (Bowles, 2002). Some factors can mask the results, such as the type of lighting (incandescent, high frequency or low frequency fluorescent light) (Evans et al, 2012) and light intensity during the day and at night. Very low light intensities (0.3 lux) can affect bird’s seasonal cycles (Kempenaers et al, 2010; Dominoni et al, 2013)
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