Relationship between duration and intensity of environmental light on the growth performance of male turkeys

In each of two trials a 2 x 2 factorial arrangement of treatments was used to evaluate the growth response of tom turkeys to environmental light. The main experimental light treatment factors were: daylength [23 h light (L):1 h dark (D) vs. 8 h L:16 h D] and light intensity (10.8 lx vs. 108 lx). There were 100 toms in each treatment; all birds were in closed confinement floor pens exposed to artificial light only. Data were collected for growth performance evaluations at 2 to 4-wk intervals to 22 wk of age. No significant daylength x intensity interactions occurred in the study. No consistent effect of daylength or light intensity on body weight occurred. Light intensity had no significant effect on feed conversion but 23 h L:1 h D significantly (P less than or equal to .01) improved feed conversion from that in the 8 h L:16 h D treatment at 18 and 22 wk of age. This occurred in both trials. Neither the daylength nor the light intensity treatment effects differed with regard to livability or to incidence of leg disorders. Testicular development at 22 wk of age of birds in the two intensity treatments was similar but testes were significantly (P less than .01) larger in the 23 h L:1 h D treatment than the 8 h L:16 h D treatment. Percentage of breast yield was not influenced significantly by the daylength or intensity treatments but the amount of abdominal fat was significantly greater in the 8 h L:16 h D group than the 23 h L:1 h D group. From the results of this study it seems clear that daylength can have an important impact on the growth performance of tom turkeys whereas variations in light intensity ranging from 10.8 to 108 lx generally resulted in negligible differences in response.