Improvements in modern broiler housing have substantially reduced air leakage, making proper operation of ventilation systems critical to maintaining a suitable environment, according to Joseph L. Purswell of the USDA-ARS Poultry Research Unit in Mississippi State and his co-authors there and at Mississippi State University in a paper published recently in International Journal of Poultry Science. Fuel prices have increased in recent years, they added, leading to reduced minimum ventilation in order to conserve fuel, which increases carbon dioxide (CO₂) concentrations within the house.

Previously, some adverse effects have been observed on the performance or mortality of broilers up to 14 or 28 days of age with high concentrations of carbon dioxide by these and other researchers.

The Mississippi-based scientists conducted four trials to assess the effects of increased carbon dioxide concentrations on birds aged 28 to 49 days. Each trial used 300 straight-run broilers placed in environmentally controlled rooms, in which carbon dioxide concentrations were maintained with no added carbon dioxide (control); 2,500ppm at all times; 2,500ppm (day) and 4,500ppm (night); or 2,500ppm (day) and 6,500ppm (night) from 28 to 42 days of age.

The group reports that they observed no differences in live production – in terms of body weight, body weight gain, feed intake and feed conversion – or processing yields between the treatments. However, they did observe that broilers in the variable temperature treatments tended to have numerically higher bodyweights, bodyweight gain and feed intake. Furthermore, although no significant differences were found in processing and yield data, there was a significant differences in breast fillet weight; breast fillet yield relative to carcass weight was not affected by treatment, however.

Purswell and co-authors concluded that analysis of ventilation rates to maintain the test conditions for a commercial broiler house showed that while supplemental heat requirements are lower with reduced ventilation needed to maintain either 4,500 or 6,500ppm, the associated ventilation rates are inadequate for moisture removal.

Using current engineering design guidelines, ventilation rates used to control moisture will usually exceed that required to maintain carbon dioxide concentration at reasonable levels, the authors commented.

Reference

Purswell J.L., J.D. Davis, B.D. Luck, E.J. Kim, H.A. Olanrewaju, A.S. Kiess and S.L. Branton. 2011. Effects of elevated carbon dioxide concentrations on broiler chicken performance from 28 to 49 days. International Journal of Poultry Science 10 (8): 597-602.

Further Reading

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November 2011