Effect of nutritional pen construction on the thermal performance of broilers

Nutritional test pens are commonly used to segregate and geolocate birds in commercial-scale broiler houses to control spatial variation from the environment. Pens should subject test birds to similar environmental conditions as birds roaming free in the house, however, discussions on pen construction materials, design, and placement have focused on durability and handling with little regard for the pen's thermal environment. Simulated birds were constructed with a metal bowl and a light bulb heat source to mimic the heat generation of large commercial broilers. Bowl surface temperature (BST) was measured as a model for the surface temperature of a broiler housed in a nutritional pen. Effects of panel open area (100% (control), 89%, 85%, 70%, 50%, and 30%) and air velocity (2, 3, and 4 m/s) were factorially tested on BST in a wind tunnel. Panels with an open area of less than 70% were different (P < 0.0001) from free air (100% open area). There was a difference of 5°C (9°F) for BST between the most restrictive panel (30%) and free air (100%), demonstrating a large difference in the thermal environment that birds might experience if air is restricted. Air velocity treatments were different (P < 0.0001) with mean BST increasing as air velocity decreased. Panels should be constructed with open areas greater than 70% accounting for structural framing and other obstructions as well as expected dust accumulation. While pen durability and handling are important for on-site success, these parameters should not overshadow restrictive airflow pen designs that would potentially alter thermal environmental conditions in nutritional treatment comparisons.

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