Drs Roger J. Lien, Joe B. Hess and Sarge F. Bilgili of the Poultry Science Department at Auburn University have examined the influence of lighting programmes consistent with European and US guidelines on broiler performance and stress responses. Their research was sponsored by the US Poultry & Egg Association.

When this work was initiated, National Chicken Council (NCC) guidelines indicated that broilers be provided four hours of darkness daily, except during the first and last two weeks of rearing. The NCC also recommends using lighting to manage growth, and lower intensity when near continuous light is used. European Union (EU) guidelines require six hours of darkness daily, except during the first seven and last three days of rearing, and at least two foot-candles (FC) intensity.

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The trend in the US is towards greater light intensities and shorter photoperiods, as evidenced by recent NCC guideline changes requiring four hours of darkness for an additional week. Pressure for change has come from customer organisations and consumers concerned with animal welfare. Few studies have simultaneously documented effects of shorter photoperiods and higher intensities on live performance, measures of mobility, processing characteristics and stress responses of broilers.

This project's objectives were to determine effects of lighting programs consistent with EU and NCC guidelines on broiler; 1) live and processing performance, 2) mobility and 3) stress responses. Two trials were conducted on male broilers of tray pack and breast yield strains. In Trial 1, long-bright and long-dim programmes meeting NCC guidelines were compared to a split dark-bright program, which met EU guidelines. In Trial 2, an increasing-dim programme meeting NCC guidelines was compared to increasing-bright and split dark-bright programs, both of which met EU guidelines.

There were no negative impacts on live performance due to lighting programmes tested, reported Lien and colleagues.

Potential negative effects of reducing photoperiods to 18 hours per day were alleviated by splitting the dark period into two blocks. Compensatory growth allowed broilers on increasing lighting programmes to attain comparable slaughter weights, although there was evidence that some strains may not fully recover.

Breast yield was lower in the increasing lighting programmes compared to the split dark-bright programs of shorter constant photoperiod.

Mobility was increased by shorter photoperiods and increased intensity: however, there was no consistent influence on measures of walking, standing ability or foot scores.

Although stress measures were generally unaffected by lighting programmes, there were a few measures that may indicate that greater intensity and longer or changing photoperiods may be more stressful.

While it is difficult to quantify the economic impact of their findings, the Auburn researchers say they should aid broiler managers in developing lighting programmes that maximise efficiency while complying with NCC guidelines, and provide policy makers with valuable scientific data to on which to base future guidelines.

Photoperiod and intensity differences studied can easily have an impact on breast meat yield worth in the realm of $1.3 million per year to an average US broiler complex.

November 2010