Diurnally cycling temperature and ventilation affect young turkeys' performance and sensible heat loss

The goals were to elucidate the effects of ventilation rate (VR) coupled with exposure to constant 20 degrees C or to diurnal temperature cycling on young turkeys' performance and sensible heat loss (SHL). In three experiments male British United Turkeys (BUT), from 3 to 6 weeks of age, were exposed to constant 20 degrees C, or to 35/25 degrees C or 30/20 degrees C diurnal temperature cycling, all at 50% RH and with VR (expressed as air velocity (AV)) ranging from 0.8 to 3.0 m s(-1). The 2nd and 3rd of these experiments included a positive control at constant 30 degrees C and VR of 1.5 m s(-1). Weight gain, feed intake, and feed efficiency were measured or calculated, as appropriate; SHL was calculated from measured surface temperature, and plasma concentrations of triiodothyronine (T-3) was determined in the 1st experiment. Changes of VR at constant 20 degrees C did not affect performance, but total SHL increased significantly with increasing VR. Under the 35/25 degrees C regime a significantly higher BW was recorded, with a similar pattern of feed efficiency, when VR during the hot part of the cycle was 1.5 or 2.0 m s(-1) than when it was 0.8 m In the 3rd experiment, BW in the 35/20 degrees C treatment was significantly lower than that of the controls. In all experiments, turkeys maintained body temperature (T-b) within the normothermic range, and SHL varied with VR. It can be concluded that although diurnal temperature cycling reflects the natural situation, exposing young turkeys to constant 30 degrees C combined with optimal ventilation might yield the best performance results. (C) 2011 Elsevier Ltd. All rights reserved.