Surface wetting and its effect on body and surface temperatures of domestic laying hens at different thermal conditions.

This study investigated the efficacy of surface wetting at different thermal conditions on core body, head, and dorsal surface temperatures in laying hens. Hens were sprinkled on the head and dorsal surface by releasing a sprinkling dosage of 10 mL.bird(-1). The first measurement was taken presprinkling, and the second was taken immediately postsprinkling and then repeated every 5 min for 20 min. The cooling water needs for intermittent partial surface wetting to relieve acute heat stress in the laying hens were quantified for 48 domestic laying hens under 4 experimental thermal conditions. The hens were kept at 4 thermal conditions at average dry-bulb temperatures of 31.30 +/- 0.03, 33.20 +/- 0.08, 36.01 +/- 0.12, and 40.24 +/- 0.08 degrees C; RH of 67.68 +/- 0.37, 51.78 +/- 1.98, 24.59 +/- 0.90, and 16.12 +/- 1.55%; and air velocities of 0.09 +/- 0.00, 0.07 +/- 0.00, 0.08 +/- 0.00, and 0.09 +/- 0.00 m.s(-1), respectively. The differences in core body, head, and dorsal surface temperatures among the 4 thermal groups were 0.15, 0.18, 0.23, and 0.22 degrees C for core body temperature; 1.63, 1.44, 2.51, and 0.97 degrees C for core head temperature; and 1.23, 1.37, 1.41, and 0.64 degrees C for core dorsal temperature at thermal conditions 1, 2, 3, and 4, respectively. There were significant differences in core body, head, and dorsal surface temperatures among the 4 thermal condition groups. It was concluded that the spraying interval was directly proportional to the product of the vapor pressure deficit and the thermal resistance of convective mass transfer of the wetted hens, because there were no significant differences in the air velocity among the 4 thermal condition groups and the air velocity was very low.