Growth Responses of Male Broilers Subjected to High Air Velocity for either Twelve or Twenty-Four Hours from Thirty-Seven to Fifty-One Days of Age

Heat stress contributes to increased late-mortality and decreased growth of broilers grown during hot weather. Tunnel ventilation is commonly used to alleviate heat stress by increasing sensible heat loss. As broilers approach heavy BW (>2.5 kg) in hot weather, operating tunnel ventilation continuously as opposed to only during times of high ambient temperature may improve growth rate and nutrient utilization. This study evaluated growth responses of male broilers subjected to high air velocity (2.79 m/s) for either 12 or 24 h from 37 to 51 d of age. The experimental treatments were 1) control (still air), 2) air velocity of 1.65 m/s (325 ft/min) for 12 h and 2.79 m/s for 12 h, and 3) air velocity of 2.79 m/s (550 ft/min) for 24 h. A cyclical temperature regimen of 25–30–25°C (77–86–77°F) was used with a constant 23°C dew point. Providing continuous high air velocity of 2.79 m/s from 37 to 51 d of age led to a 112-g increase in BW gain and decreased feed conversion ratio by 15 points compared with subjecting broilers to high air velocity of 2.79 m/s for only 12 h. Broilers subjected to both high and low air velocity improved BW gain, feed consumption, and feed conversion over the control birds. These results indicate that continuous ventilation at high air velocity improves BW gain and feed conversion ratio of heavy broilers during the last 2 wk of the grow-out.