Nutrition and management of heat-stressed pullets and laying hens

Maximum daily temperatures in excess of 30 degrees C are common in many table egg-producing regions of the world. Such temperatures require the application of specialized management and nutrition if laying hens are to produce eggs near their genetic potential. Environmentally-modified buildings have been shown to be especially advantageous for commercial layers that are housed in high density cage facilities. Directing air movement onto floor-housed birds has also been found to maximize heat loss and was beneficial as long as the air temperature did not exceed body temperature. This latter procedure was especially useful where sporadic incidences of heat stress were common. Nutritional manipulation of the diet also offers advantages, especially in overcoming problems of reduced appetite. This principle has been shown to apply to both growing pullets and adult layers. Recent research has confirmed that optimum production during lay depends on the adult hen having an adequate gut capacity and sufficient nutrition during rearing. Egg production during moderate heat stress can be improved by increasing the intake of protein relative to energy but energy requirements will likely increase in severe heat stress. Dietary supplementation with ascorbic acid and vitamin E and a supply of cool drinking water have also been reported to improve production during lay but the response to the latter treatment varied with genotype.