Effects of lighting program on reproductive development of female large white turkeys
1999
Melnychuk, V.L. | Robinson, F.E. | Renema, R.A. | Hardin, R.T. | Emmerson, D.A.
Female commercial turkeys were used to investigate the effects of lighting program on onset of egg production, reproductive development and egg production. Under a conventional (CON) lighting program, birds were photostimulated from 5L:19D to 14L:10D at 29 wk, with an additional hour of daylight added at 35 wk of age (15L:9D). The alternate (ALT) lighting program involved weekly 0.5-h decreases in day length from 14L:10D at 3 d to 6L;18D, at 17 wk followed by weekly 0.5-h increases in day length beginning at 20 wk, to a maximum of 15L:9D at 38 wk of age. Birds were killed either at 3-d intervals (l40-206 d), to assess reproductive development, or on the day following the first oviposition. A final group of birds was maintained for egg-production records. The ALT birds reached first egg at a younger age (220 d vs. 224 d) and lower body weight (11.18 kg vs. 11.88 kg) than CON birds did. The oviduct of the CON treatment reached its mature weight 5 d before the ovary. The growing oviduct of the ALT birds reached its mature weight 4 d after the ovary. Ovarian development of the ALT birds was accelerated by 10 d, compared with that of the CON birds. The number of unreconciled ovulations, as evidenced by post-ovulatory follicles at first oviposition, did not differ between treatments (1.2, ALT; 1.6, CON). The number of large follicles was not different between the two treatments (12.9, ALT; 14.3, CON [P = 0.092]). First-egg weights were significantly lower (70.6 g, ALT; 77.2 g, CON) for the ALT treatment, which also had a higher incidence of small eggs for the first 4 wk of production (3.31%, ALT; 0.82%, CON). Total egg production and total settable egg-production did not differ between treatments.
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