Effects of light environment and population density on growth performance of male turkeys.

This study was designed to determine the effects of various light environments on the growth performance of male turkeys reared under two extremes of population density. Environmental lighting had subtle but persistent effects on growth performance. Low-intensity illumination consistently improved body weight gains during early growth periods while high-intensity illumination improved body weight gains during the later growth period. Intermittent lighting, especially at a light intensity of 86.1 1x, caused precocious sexual development and appeared to stimulate growth after 18 weeks of age during cool weather and after 12 weeks during warmer weather. Diurnal, blue-filtered light improved weight gains during early growth periods compared to either white- or red-filtered diurnal light, while white- or red-filtered light tended to improve weight gains during the later growth period. Floor space allowances studied had no significant effect on growth or feed efficiency prior to 12 weeks of age. At that time, high population density caused lower body weight gains, lower feed efficiency, poorer feathering, a higher incidence of downgrading, and higher mortality than did a relatively low population density. Different light environments [intermittent (2L:2D) white light and diurnal (12L:12D), white-, red-, or blue-filtered light] were ineffective in altering the responses of turkeys to crowding. There was, however, a significant interaction of light intensity with population density. This interaction indicated that high light intensity allowed maximum expression of growth potential in a low population density environment but reduced growth under high population density pressures.