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Submitted to: IFAC/CIGR Workshop
Publication Type: Proceedings Publication Acceptance Date: 10/18/2009 Publication Date: 10/21/2009 Citation: Purswell, J.L. 2009. Effects of air velocity on broiler production. IFAC/CIGR Workshop . CD 1. Interpretive Summary: Modern poultry genetics have increased growth rates and heat production. White meat demand in the U.S. has driven increases in market weights over the last several years, resulting in increased ventilation needs. A review of the literature has shown dramatic increases in productivity and production efficiency when flocks are exposed to high air velocities (> 2.0 m/s). Increasing air velocities improve both body weight and feed conversion, as well as reducing time to reach market weight. However, few recommendations for design of high air velocity ventilation systems were found, indicating a need for updating design literature for modern broiler housing. Technical Abstract: Recent improvements in poultry genetics have resulted in increased growth rates (Havenstein et al., 2003) and total heat production (Chepete and Xin, 2001; Xin et al., 2001). In addition, market weights have also increased with white the meat demand of the U.S. resulting in birds being marketed at body weights exceeding 3.6 kg (8 lb). Due to these increases in growth rates and heat production, air velocity has become a critical management component in meat poultry production. Mechanical ventilation has traditionally been used as a tool to limit temperature rise in a structure when natural ventilation was inadequate. The addition of evaporative cooling provides an economical means to lower air temperature. However, air movement is the most practical means to provide cooling when evaporative cooling is limited (Smith, 1981). Increased air velocity results in increased sensible heat loss from the bird via convective heat transfer (Mitchell, 1985; Timmons and Hillman, 1993, and Simmons et al., 1997). Wide-scale adoption of tunnel ventilation systems in the past 20 years has eliminated the velocity limitations of cross-ventilated housing systems and allowed for increasingly higher air velocities as production practices have evolved with bird genetics and market weights. Ventilation system design guidelines typically suggest overall ventilation rates (volumetric flow) as opposed to air velocities. While these guidelines are helpful in the context of limiting temperature rise within the structure, the integrated broiler industry in the Southeastern U.S. continues to increase fan capacity in excess of that dictated for temperature control. Design of hot-weather ventilation systems in modern broiler housing in the Southeastern U.S. has been driven by improvement in live performance and yield as a consequence of increasing air velocity. |
