Abstract
This study evaluated effects of photoperiod treatments on slaughter and carcass traits, meat quality, indicators of oxidative stress, and heat shock protein 70 (Hsp70) levels of lung and heart tissues in broilers. Five hundred Ross 308 broiler chicks were used. The treatments consisted of 23 hours of continuous light and one hour of darkness (23L1D), four hours of light followed by two hours of darkness (4L2D), eight hours of light and four hours of darkness (8L4D), and 16 hours of light and eight hours of darkness (16L8D). After 42 days, two birds from each replicate were slaughtered. Birds that had been subjected to 16L8D had lower slaughter, carcass, and breast weights than the other treatments. Significant correlations were observed for slaughter, carcass and breast weights and white stripe. At 10 min post mortem, the pH of the breast was the highest in 23L1D. Breasts from birds subjected to 23L1D and 16L8D had most fat and least protein, while white striping was not different among treatments. The 4L2D treatment resulted in the highest lung glutathione (GSH) concentration. Malondialdehyde (MDA) and GSH concentrations in the heart tissues of broilers from 8L4D and 4L2D were greater than those from 23L1D and 16:8. Glutathione peroxidase (GSH-Px) and superoxide dismutase concentrations were greatest for birds subjected to 16L8D. Heat shock protein 70 was lowest in lung and heart from birds subjected to 8L4D. Thus, shorter and more frequent periods of darkness can be recommended for welfare with little compromise in performance.
 Keywords: carcass quality, heat shock protein 70, oxidative stress, white stripe
Highlights
Lighting is an important management technique in broiler production
Sudden death syndrome (SDS), pulmonary hypertension syndrome (PHS), leg abnormalities, and abnormal eye development can all be reduced with intermittent lighting (Ononiwu et al, 1979; Li et al, 2000; Skrbic et al, 2015)
The 16L8D treatment resulted in a lower slaughter, carcass (P
Summary
Lighting is an important management technique in broiler production. Studies on lighting in broilers have focused on photoperiod, wavelength and light intensity (Deep et al, 2010; Mosa et al, 2015). These factors influence broiler performance and their welfare. Many companies implement continuous or nearcontinuous lighting regimens to maximize growth rate and feed intake (Olanrewaju et al, 2013). Low light intensities and increasing photoperiods have positive effects on broiler performance and feed conversion (Lien et al, 2007). Continuous lighting causes metabolic syndromes, which compromise the welfare of broiler chickens (Manser, 1996; Julian, 2000). The European Union (EU) has mandated that birds should be reared with lighting that follows a 24hour rhythm and includes periods of darkness that last at least six hours in total, with at least one uninterrupted period of darkness of at least four hours (EU, 2007)
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