Ahemeral lighting of turkey breeder hens. 3. Temporary application and early age at lighting

Ahemeral (non-24 h) light-dark cycles are known to increase egg size but when applied continuously have adverse effects on egg production. The purpose of this experiment was to determine whether temporary application of ahemeral light-dark cycles (AH) can overcome the adverse effects of continuous AH and provide improved reproductive performance of turkey hens photostimulated at an early age. Of particular interest was the effect of temporary AH on increasing egg weight at the start of lay because decreased egg weight is a major problem associated with early lighting of turkey hens. The AH treatments started at 26 wk of age and were given for 2 wk, 5 wk, or continuously. Each consisted of 15 h of light per cycle with a cycle length of 28 h duration, that is, 15 h light (L):13 h dark (D). The experiment was started in the winter season and continued for 28 wk. The following variables were measured: BW, feed intake, onset and rate of lay, fertility, hatchability, incidence of floor eggs, egg weight, poult production, and poult weight. It was clear that 5 wk or more of AH followed by standard lighting (15L:9D) increased initial egg weights from those of 26-wk controls and were similar to those of 30-wk controls. This effect was temporary, as it was absent by 8 wk of photostimulation. Also, cumulative eggs per hen to 54 wk of age were increased by 5 wk of AH treatment as compared to those of controls photo-stimulated at 30 wk of age. These eggs had normal fertility, hatchability, and poults per hen in two evaluation periods. A high incidence of AH floor eggs was reduced to that of the controls following a shift to standard light-dark cycles. We concluded that temporary use of AH at the start of photostimulation is better than continuous use of AH throughout lay and resulted in improved reproductive performance of hens photostimulated at an early age.