Drinking water temperature effects on laying hens subjected to warm cyclic environments

Two experiments were conducted to evaluate the effects of drinking water temperature (T-w) on laying hens subjected to warm cyclic air temperature (T-a) conditions. Each experiment consisted of a 1-wk acclimation under thermoneutrality (TN) (T-a = T-w = 21 C), a 4-wk heat exposure or treatment period, and a 2-wk recovery under TN. Each experiment involved 24 individually caged hens at the initial age of 29 wk (Experiment 1) or 30 wk (Experiment 2). In Experiment 1, T-w of 18 or 27 C was provided to 12 birds per T-w regimen under a diurnal T-a of 27 to 35 C (daily mean of 31 C). In Experiment 2, T-w of 15, 19, 23, or 27 C was provided to six birds per T-w regimen under a diurnal T-a of 27 to 38 C (daily mean of 32.5 C). Experiment 1 showed that T-w of 18 C enhanced hourly and daily feed and water intake during the first 2 wk of heat exposure, as compared with T-w of 27 C. Experiment 2 showed that daily feed and water intake were greatest for hens in the 23 C Tw regimen and least for hens in the coolest or warmest T-w regimens. Reduction in daily feed intake with increase in daily mean T-a ranged from 2.0 similar to 3.2 g/C-day (first week of heat exposure) to 1.1 similar to 1.9 g/C-day (fourth week of heat exposure). Water to feed intake ratio was 1.8 similar to 2.0 during acclimation and recovery, but increased to 3.0 similar to 3.4 during heat exposure. Internal egg quality parameters were in general unaffected by T-w. The two warmer T-w regimens in Experiment 2 had less reduction in egg size than did the two cooler T-w. In both experiments, hens displayed anticipatory increase in feed and water intake 2 to 3 h prior to lights-off. However, the stimulus of lights-on did not elicit a strong return to feed and water consumption as typically seen in broilers. The results revealed the potential existence of an optimal T-w range (near 23 C) for heat-challenged laying hens. Larger-scale tests are warranted to further verify the findings.