Effects of light source, ambient temperature, and dietary energy source on the general performance and incidence of leg abnormalities of roaster chickens.

A 2 X 3 X 4 factorial experiment was designed to test the effects of two light sources (incandescent vs. fluorescent), three weekly ambient temperature decrements of 4.5, 3.0, or 1.5 C (from 34.5 to 20 C), and four dietary energy regimens on the general performance and incidence of leg abnormalities of roaster chickens. Light source had no significant effect on mortality, body weight, or feed conversion. Incidence of angular deformity (AD) and total leg abnormalities (TLA) was lower and tibial dyschondroplasia (TD) was higher (P less than .05) for roasters reared under fluorescent as opposed to incandescent light. Cooler ambient rearing temperatures increased (linearly) the incidence of mortality, curly toes (CT), AD, enlarged hocks (EH), and TLA but resulted in a linear decrease in TD and had a detrimental (linear) effect on feed conversion. Dietary energy had no significant effect (P greater than .05) on mortality or leg abnormalities except for CT, (wherein there was decreased incidence with increasing dietary energy) or final live weight, but overall (to 70 days) increasing dietary energy resulted in a linear improvement in feed conversion. Mean monetary returns were nonsignificantly better for roasters reared under fluorescent vs. incandescent light (ca 8 cents/bird) and were better for birds reared under warm versus cool ambient temperatures (ca 10 cents/bird). Increasing dietary energy resulted in a linear increase in monetary returns.