Effects of lighting program on reproductive development of female large white turkeys

Abstract

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 (140–206 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 postovulatory 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. Key words: Turkey, sexual maturation, lighting program, ovary, oviduct