Akademik Veri Yönetim Sistemi
Avian and Poultry Biology Reviews, cilt.13, sa.4, ss.242, 2002 (SCI-Expanded)
Optimum turning of eggs during incubation has been of interest almost since the first observations of the incubational habits of feral fowl. Considerable research has been directed at determination of the times during incubation when turning eggs was most critical to obtain maximum hatchability. In an early study, Card (1926) maintained that eggs turned solely during the first 6 days of incubation hatched almost as well as eggs turned throughout incubation. New (1957) turned eggs twice daily from 4-7 days and found that these eggs hatched as well as those turned throughout incubation. Deeming et al. (1987) and Deeming (1989) agreed with New (1957) that the most critical period for turning was from 3-7 days of incubation. Wilson (1991) reported that three time periods (1-3 days, 4-7 days, and 7-14 days) have been proposed as the most critical for turning of chicken eggs. The objective of the present study was to closely examine the effects of an absence of turning throughout incubation in order to establish the critical periods for turning broiler hatching eggs from a modern strain of commercially available broiler breeders during incubation under commercial conditions. Broiler hatching eggs were collected four times daily and stored for 1-3 days at 18°C before being set in a commercial hatchery. All eggs were turned 24 times per day during incubation except as required for each specific treatment. In Experiment 1, 7,200 eggs were collected from flocks at 29 and 68 wk of age. The treatment groups were either turned or not turned during the 0-7 day, 8-14 day, and 15-18 day periods in eight regimens that included all possible turning combinations. Each tray of 150 eggs represented a replicate and three replicate trays (450 total eggs) were used per turning treatment. The absence of turning from 0-7 days of incubation caused the greatest decrease in fertile hatchability and greatest increase in all stages of embryonic mortality and the incidence of Malposition II (head in small end of shell). A significant turning treatment by flock age interaction showed that the 0-7 day effect was more pronounced in the 68 week-old flock as compared to the 29 week-old flock used in the experiment. In the two trials of Experiment 2, 9,600 eggs from each of 33 week-old (Trial 1) and 35 week-old (Trial 2) broiler breeder flocks were either turned or not turned from 0-2 days, 3-4 days, 5-6 days, or 7-8 days in 16 regimens that included all possible turning combinations. In both trials each tray of 150 eggs was a replicate for treatment and control groups. Four replicate trays (600 total eggs) were used per turning treatment. Generally, the absence of turning from 3-8 days, or 0-2 days alone or in combination with other time periods reduced hatchability of fertile eggs and increased embryonic mortality and the incidence of Malposition II. The 3-8 day period has been typically associated with the formation of the sub-embryonic fluid while the 0-2 day period was apparently more associated with dynamics of early changes in the shell membranes and albumen. The present data are in agreement with the early study of Card (1926) who reported that unturned eggs hatched poorly compared with eggs turned during the first 6 days of incubation but differ somewhat from other reports (New, 1957; Deeming et al., 1987; Deeming, 1989) that reported the most critical period for turning to be between either 3-7 days or 4-7 days of incubation. It was concluded that the most critical period for turning commercial broiler hatching eggs during incubation was from 0-7 days with the single most critical 2-day period being 0-2 days.