COOLING LAYING HENS BY INTERMITTENT PARTIAL SURFACE SPRINKLING

This study investigated the efficacy of intermittent partial surface sprinkling to cool caged layers at 20, 38,and 56 weeks of age. Ten birds were used per age group with two birds per paired trial (Experiment, Expt, and Control,Ctrl) that were subjected to an acute heat exposure of 40.0 0.5C air temperature, 45 3% RH, and air velocity of 0.15to 0.20 m/s for a maximum of 8 h. The Expt birds were sprinkled with water mist (8 mL/sprinkling session) on the headand appendages at 15-min intervals from the time when panting was observed; whereas, the Ctrl birds received nosprinkling. Continuous measurement of the rectal temperature and periodic thermographical measurement of the surfacetemperature of the birds were performed. The intermittent partial surface sprinkling had the following merits as comparedwith the control: lower body temperature rise (4.3 vs 5.7C; P < 0.05), higher lethal heat load threshold (10.0 vs 6.6C-h,P < 0.05), longer survival time (145 to > 480 vs 92 to 266 min), and reduced mortality (20 to 60% vs 100%). Themaximum reduction in surface temperature of the head and appendages due to the sprinkling averaged 2.2C. Under thepresent environmental conditions (i.e., 40C, 45% RH, and 0.15 to 0.20 m/s), sprinkling once every 5 to 6 min wouldprovide adequate cooling to prevent the surface temperature from rising. The concept of body heat load ( ) seems toprovide an effective measurement of heat tolerance of the birds under different cooling schemes.