A study of the employment of melatonin supplementation and darkness regime on reducing the negative effects of acute heat stress and mortality in broiler chickens

BACKGROUND: Heat stress is one of the most important environmentalstressors challenging poultry production worldwide.Understanding and controlling environmental stressors is crucialfor successful poultry production. OBJECTIVES: The aimof the present study was to investigate the effects of melatoninsupplementation and darkness regime on reducing the negativeeffects of heat stress in broiler chickens. METHODS: A total of400 broiler chickens (Arian) were obtained and subjected tofour different groups. The control chickens were grown in normalconditions without receiving any treatment. The positivecontrol birds were grown similar to the control but exposedto an acute heat stress for 6 h/d from days 35 to 40. The darkgroup chickens were reared under a dark schedule and exposedto heat stress. The birds of the fourth group were reared similarto the positive control but received 40 ppm melatonin in thediet from days 30 to 40 of age. Dead birds were autopsied. Theweekly growth performance of chickens was determined andblood samples were taken for hormonal analysis. RESULTS: Thenumber of dead birds due to heat stress was significantly decreasedin chickens subjected to the dark program and/or thosewhich received melatonin in the diet compared with those ofpositive control chickens. Such differences were accompaniedwith the significantly lower levels of plasma T3, T3/T4and corticosterone in these groups of chickens. Additionally,plasma thiobarbituric acid reacting substances level was significantlyhigher in positive control broilers compared to theircounterparts. CONCLUSIONS: Our findings indicate a reductionof metabolic rate and heat production in dark regime and melatoninsupplementation that can reduce the side effects of heatstress and, therefore, reduce the mortality rate.

کلیدواژه ها:

broiler chickens ، corticosterone ، heat stress ، melatonin ، T3/T4