Effects of fasting on heat-stressed broiler chickens: part I- growth performance, meat quality, gut histomorphological and microbial responses

The current study aimed to optimize the fasting duration in order to mitigate the detrimental effects of heat stress on broilers raised in hot and humid climatic environments. A total of 500 broiler DOCs were assigned to five distinct treatment groups: Tₒ= Non-fasted controlled temperature (24-26℃) (NF-CT), T 1 = Non-fasted heat stressed (30-38℃) (NF-HS), T 2 = 6 hours fasted heat stressed (6-h FHS), T 3 = 8 hours fasted heat stressed (8-h FHS), and T 4 = 10 hours fasted heat stressed (10-h FHS). Each treatment was replicated five times, with 20 birds in each replicate group. As expected, the birds in NF-CT group showed significantly better performances for all the growth parameters, although birds who fasted for 8-h under heat stress exerted better growth and FCR in comparison to the other HS groups. Fasting of birds under heat stress significantly showed the lowest mortality. Like the NF-CT group, birds in 8-h FHS achieved significantly higher dressing percentage, breast meat, liver yields, and the lowest abdominal fat. Fasting for 8- and 10-h significantly increased breast meat pH and water holding capacity and thus reduced cooking loss. Fasting also improved the breast meat color quality by increasing redness (a*) and reducing the hue angle values comparable with the NF-CT group. A significantly upward trend in villi height (VH), width (VW) and crypt depth (CD) of gut segments was also observed in the birds of the 8-h FHS group. Total bacterial and coliform counts in cecum contents were reduced significantly with the increase in the fasting period. Benefit-cost analysis showed better profitability in the 8-h FHS group than other HS groups. Taken altogether, it can be concluded that broiler chicken exposed to 8-h fasting period is an effective approach to mitigate heat stress under hot and humid climatic conditions.