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Figure 1. Heat Loss to Wind Chill vs Respiration at Different Wind Speeds – 5 lb Birds at 85°F

Figure 1 is based on research showing how important wind chill is in keeping birds comfortable and gaining weight.

At an air temperature of 85°F, five-pound birds will be suffer- ing from excess body heat in still air and will have to be panting to shed that excess heat (left side of chart). As wind speed increases (toward right side of chart), they are able to shed enough of their body heat through wind chill so that they can resume normal breathing (and eating).

Figure 2. Wind Chill Effects for 4-Week and 7-Week Birds

Figure 2 illustrates research showing just how differently younger birds experience wind chill cooling. At an air temperature of 90°F, the effective temperature felt by four-week birds as tunnel wind speed increas- es will be 3 to 8 degrees lower than the effective temperature experienced by mature birds. The effect is even more pronounced for 1-day to 3-week birds because of their smaller body size and lack of feathers.

First, run vent fans through perimeter inlets (tunnel curtain closed). Tunnel should be the last resort. Try to get the birds comfortable in the vent door ventilation mode. If you cannot get the birds comfortable (still panting) consider tunnel ventilation. With very young birds tunnel needs to be done carefully. You need to be there on the farm to observe the birds. If the birds are hot they can benefit from tunnel but because they are young, very small in mass, and have few feathers, we must tunnel them gently. Two-fan tunnel ventilation with vent doors closed and tunnel inlet opened half way would be a good starting point.

Windspeed with two fan tunnel might be somewhere around 100-120 fpm depending on fan size and other variables. Watch the birds for at least 30 to 45 minutes to see how they react. Adding one more fan for a total of three fan tunnel (150-180 fpm wind speed) might be the next step to try. Adding any more air speed

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