|Dozier iii, William|
Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/11/2005
Publication Date: 8/5/2005
Citation: Dozier III, W.A., Lott, B.D., Branton, S.L. 2005. Live performance responses of male broilers subjected to constant or variable air velocities at moderate temperatures with a high dew point. Poultry Science. 84:1328-1331. Interpretive Summary: The broiler industry produces 8 billion birds annually. Heat stress is prevalent with broilers approaching marketing during summer months. The largest contributor to heat production is the bird itself. Applying air velocity over broilers ameliorates heat stress conditions. While previous research has demonstrated improved broiler growth rate as constant air velocity increased from 120 to 180 m/min under moderate (25-30-25 C) temperatures, determining growth responses of broilers subjected to a constant air velocity or increasing air velocities as the bird advances in age under moderate temperatures (25-30-25 C) has not been investigated. However, applying constant air velocity of 180 m/min from 21 to 49 d of age would potentially remove excess sensible heat, thus adversely affecting feed conversion. Additionally, maintaining constant high air velocities would increase electrical cost. This research evaluated a constant air velocity of 120 m/min or a wind tunnel having variable air velocity (90 m/min from 28 to 35 d; 120 m/min from 36 to 42 d, and 180 m/min from 43 to 49 d). It was determined that increasing air velocity from 120 to 180 m/min did improve BW gain of broilers from 42 to 49 d of age, but increasing air velocity from 90 to 120 m/min did not provide benefits with growth from 28 to 35 d of age. Contract growers are paid on the basis of live body weight and the 60 g difference in body weight translates to an economic advantage of $0.007 per bird in addition to the savings attributable to improved final body weight.
Technical Abstract: This study examined the effects of varying air velocities vs. a constant air velocity with a cyclic temperature curve of 25-30-25 C and a dewpoint of 23 C on broilers from 28 to 49 d of age. Four replicate trials were conducted. In each trial, seven-hundred and forty-two male broilers were randomly allocated to six floor pens or two air velocity tunnels each tunnel consisting of four pens. Bird density, feeder, and waterer space were similar across all pens (53 birds/pen; 0.07 m2/bird). The treatments were control (still air), constant air velocity of 120 m/min, and variable air velocity (90 m/min from 28 to 35 d, 120 m/min from 36 to 42 d, and 180 m/min from 43 to 49 d). Growth responses between the air velocity treatments were similar from 28 to 35 and 36 to 42 d of age. Increasing air velocity to 180 m/min improved (P ' 0.02) growth rate of broilers from 43 to 49 d of age over birds receiving an air velocity of 120 m/min, but the incidence of mortality was not affected. Subjecting birds to air velocity improved BW gain, feed consumption, and feed conversion during each weekly interval from 28 to 49 d of age. These results provide evidence that increasing air velocity from 120 to 180 m/min is beneficial to broilers weighing 2.5 kg or greater when exposed to moderate temperatures.