Effect of temporary transfers to 14 h on age at first egg in domestic pullets reared on 8-h photoperiods

Abstract

1. Brown-egg pullets were reared on 8-h photoperiods and temporarily transferred at 80 d of age to 14-h photoperiods for 2, 4, 6, 8, 10 or 12 d. Controls were either maintained on 8 h or permanently transferred to 14 h at 80 d. 2. Pullets given 8 or 12 long days matured 8-9 d earlier than constant 8-h controls, but 22-23 d later than pullets transferred permanently to long days. Mean age at first egg for the groups given 2, 4, 6 or 10 d of 14-h days were not significantly different from the 8-h controls. The mean weight of first egg and body weight at first egg for the temporarily-photostimulated groups were not significantly different from constant 8-h controls, but egg weights were > or = 5.1 g and body weights at first egg > or = 200 g heavier than the birds transferred permanently to 14 h. 3. It is concluded that up to 6 temporary long days may be given (from 80 d of age) without affecting the timing of sexual maturity, but that the provision of 8 or more long days will accelerate sexual development, thought not to the extent of a permanent transfer, in most birds within a flock. A regression analysis of the ages at which the first and last birds in the groups given 6, 8, 10 or 12 long days matured suggested that about 20 d of photostimulation are required to achieve a mean age at first egg similar to that of birds permanently transferred to long days.

Research note: an amendment to the model for predicting age at sexual maturity for growing pullets of layer strains given two opposing changes in photoperiod

“…As shown in the last column of Table 1, the values predicted by the amended model are in good agreement with the data recorded by Lewis & Gous (2006) Fig. 4.…”

“…Physiological age (as defined in the model of Lewis et al 2003) is unlikely to be fully changed until the pullets have been exposed to about 30 stimulatory daylengths when . Individual ages at first egg (#) and treatment means ($) for domestic pullets temporarily transferred at 80 days of age from 8 to 14 h for 2, 4, 6, 8, 10 or 12 day, or (¾) permanently transferred to 14 h (Lewis & Gous 2006). The horizontal line is the mean for constant 8-h and groups given 2, 4 or 6 long days, and the sloping line is an extrapolation of the regression of the means for groups given 6, 8, 10 or 12 long days.…”

“…Actual(Lewis & Gous 2006) and predicted AFE for egg-type pullets temporarily transferred at 80 days of age from 8-to 14-h photoperiods for various periods between 2 and 12 days, maintained on 8 h, or permanently transferred to 14 h at 80 days…”

“…Subsequently, Lewis & Gous (2006) reported the findings of a study in which immature domestic pullets were temporarily transferred at 80 days of age from an 8-h to a 14-h photoperiod for periods varying from 2 to 12 days. There was poor agreement ( R 2 =0·280) between recorded AFE and the AFE predicted by the earlier model (compare columns 2 and 3 in Table 1).…”

Lighting, ventilation and temperature

“…The findings subsequently explained why pullets, be they egg-type or broiler breeders, do not experience accelerated sexual maturation (Lewis and Gous, 2006). Plasma FSH concentration initially changes little, even when the increment is given at peak photosensitivity, and so gonadal development is minimally affected by such a short exposure to long days.…”