Cooling Broiler Chickens by Surface Wetting: Indoor Thermal Environment, Water Usage,and Bird Performance

Abstract. A surface-wetting cooling system was evaluated and compared to a conventional evaporative cooling system in commercial, tunnel-ventilated broiler houses during five flocks in summer months over three years. Surface wetting (accomplished using low pressure sprinklers, SPRK) and a conventional evaporative pad cooling system (PAD) were employed in adjacent houses at the University of Arkansas Applied Broiler Research Farm. With SPRK, overhead sprinklers were spaced evenly 6 m apart and 1.2 to 2.4 m above the litter surface and were intermittently operated to apply controlled volumes of large water droplets onto the birds. The SPRK house had substantially higher air temperature but lower relative humidity compared to the PAD house during critical supplemental cooling periods. During a 2-day heat stress period, the core body temperatures of birds in the SPRK house were similar to those of birds in the PAD house. The bird live weight and livability were not significantly different between SPRK and PAD with feed conversion being better in the SPRK treatment. No correlations were found between daily mortality and either daily maximum ambient temperature or flock age, indicating both cooling systems were effective in relieving heat stress of broiler chickens. Apparently, the evaporation of sprinkled water from the bird’s surface, benefiting from favorable convective conditions (intrinsically high air velocity of tunnel ventilation) and lower relative humidity, was able to compensate for higher temperatures measured in the SPRK house. Final litter moisture conditions were not significantly different. Due to the nature of the water delivery, cooling water usage per bird basis in SPRK was significantly less than that used by PAD (water in SPRK averaged 33% of that used in PAD). This represents a major opportunity for water conservation in broiler production.