Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2006
Publication Date: July 15, 2006
Citation: Dozier III, W.A., Purswell, J.L., Branton, S.L. Growth responses of male broilers subjected to high air velocity at either 12 or 24 hours from 37 to 51 days of age. Journal of Applied Poultry Research. Interpretive Summary: High ambient temperatures limits growth rate and can lead to increased mortality when broilers are grown to heavy weights. Air velocity ameliorates the adverse affects of high temperatures during summer production. This research evaluated growth performance of broilers from 37 to 51 days of age subjected to high air velocity flow (2.8 m/s; 500 ft/min) with a cyclic temperature of 25-30-25 C at either 12 or 24 h. Providing high air velocity continuously under temperatures simulating a summer production cycle resulted in a 15 point improvement in feed conversion and 9% increase in growth rate. Implementing continuous high air velocity during the last two weeks of the grow out during hot weather can provide an estimated economic benefit of $128.77/house based on electrical cost and growth rate.
Technical Abstract: 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 (2.8 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 1.5 m/s (325 ft/min) for 12 h and 2.8 m/s for 12 h, and 3) air velocity of 2.8 m/s (550 ft/min) for 24 h. A cyclic temperature regimen of 25-30-25o C (77-86-77o F) was used with a constant 23o C dew point. Providing continuous air velocity of 2.8 m/s from 37 to 51 d of age led to a 112 g increased in BW gain and decreased feed conversion ratio by 15 points compared with subjecting broilers to air velocity of 2.8 m/s for only 12 h. Air velocity improved BW gain, feed consumption, and feed conversion over the control birds. These results indicate continuous ventilation at high air velocity improves BW gain and feed conversion ratio of heavy broilers during the last two wk of the grow out.