The effect of potassium chloride supplementation in drinking water on water and feed intake and egg quality of laying hens under cyclic heat stress

This experiment was carried out to study the responses of laying hens to cyclic heat stress and the effects of potassium chloride supplementation in the drinking water on water intake, feed intake and productivity traits under heat challenge. A total of 48 hens were kept in environmental controlled chambers and randomly allocated to three experimental groups of 16 hens each. These groups were given 0, 0.2 and 0.4% KCl in drinking water for seven consecutive days. The room temperature was constant at 21 +/- 1 degrees C for one week and cycled from 21 +/- 1 degrees C to 34 +/- 1 degrees C (from 9 to 22 o'clock) for following week, then returned to constant at 21 +/- 1 degrees C for one week. Water and feed intake, egg production and egg quality of the individual hens were recorded throughout the experimental period. Body temperature was recorded at one day before, and 1(st), 3(rd), 5(th) and 7(th) day of experiment. Heat stress increased water intake, water: feed ratio, body temperature, eggshell defects in comparison with pre-heat stress. Feed intake of control and 0.2% KCl group decreased on first 3 days of heat stress. Laying rate decreased on 2(nd), 3(rd) and 4(th) day and egg weight and body weight of control group decreased during heat stress. Eggshell thickness, eggshell strength, egg deformation, yolk color and HU seem to be not affected by heat stress. In heat stress, supplementation of KCl in drinking water increased water intake, maintained body weight, egg weight and egg production, and had less eggshell defects. There was a tendency towards lower body temperature and thicker eggshell with 0.4% KCl solution. Feed intake, egg deformation, yolk color and HU were not significantly affected by KCl supplementation. These results showed that KCl supplementation through drinking water may be a means to maintain egg production and egg quality which usually occurs when the temperature in the layer house increases.