Thermal performance ofperforated pen panels for on-farmnutritional test trials

摘要

Test pens are commonly used to segregate and geolocate birds in commercial-scale broiler houses to control for spatial variation in the environment. These pens should subject test birds to similar environmental conditions outside the enclosure, however pen design and materials can vary significantly. Proportion of panel perforated area and air velocity were tested as main effects in a 6x 3 factorial design. Treatments included six levels of perforation area (100%, 89%, 85%, 70%, 50%, and 30%) and three levels of air velocity (2, 3, and 4 m s'1). Two 0.75 x 1.5 m panels were installed in a wind tunnel to simulate the upwind and downwind panels of a test pen. Sensible heat generation was simulated for birds using enclosed incandescent bulbs. A metal feeder was suspended in the center of the pen. Mean bird surface temperature (BST) and the temperature gradient between the bird and ambient temperatures (A T) were different for panel open area and increased as open area decreased. Panels should be constructed with open areas greater than 85%. BST for birds housed in pens constructed of 2.5 x 2.5 cm welded-wire mesh and 2.5 cm chicken wire were similar to free air. Panel support structure and dust accumulation must be accounted for when constructing pens. Mean BST and A T were different for air velocities of 2, 3, and 4 m s~'. Temperatures increased as air velocity decreased. Mean BST and A T were higher for birds located downwind of the test pen compared to birds in the pen. Birds downwind were 2.2"Chotter than birds in the pen making nutritional treatment comparisons difficult with the varied environment. Test pens should be duplicated axially along the house cross-section rather than longitudinally down the house. Increases in mean BST and AT willbe magnified as ambient temperatures rise above 25.4°C.