The effects of photoperiod length, light intensity, and feed energy on growth responses and meat yield of broilers

A study was conducted to assess the effects of photoperiod length (constant 23L:1D vs. a photoperiod program going from decreasing to increasing quantity of light), light intensity (bright vs. a dim, reducing intensity), and feed ME levels (low vs. high) on performance and carcass characteristics of female broilers grown to 56 d. Use of a treatment with early decreasing photoperiod followed by an increasing photoperiod reduced feed consumption and subsequent BW early. However, growth compensation occurred and feed consumption and BW were similar across photoperiod treatments by study end. Likewise, reducing light intensity (from 1 to 0.25 fc) stimulated feed consumption and a subsequent BW improvement early, as compared with high-intensity (2 fc) lighting maintained at a constant level. However, the disparity in feed consumption and BW, as influenced by light intensity, did not persist throughout the growing period. Feed conversion was not noticeably affected by photoperiod or light intensity treatments. Minimal effects of lighting were observed for carcass or part yields; however, there appeared to be a subtle substitution effect between leg, wing, and breast yield influenced by lighting program. Birds exposed to the decreasing increasing photoperiod and dim, reducing light treatments yielded more leg and wing at the expense of breast. Feeding a low ME diet resulted in increased feed consumption and feed conversion. However, birds consuming a low ME diet were more uniform. No effects of treatment on mortality were measured. These data indicate that a decreasing-increasing photoperiod can be used effectively to reduce early growth, yet allow birds to compensate as they approach market age. Low intensity lighting, however, appears to stimulate early feed consumption and growth, although this effect is transitory. Furthermore, the increased feed conversion of birds grown on the low energy diet may make its use less desirable.