CLIMATIC ADAPTATION OF LAYING HENS

Three hundred Warren Isabrown female day old chicks were raised for 18 weeks in 3 distinct artificial climates described as temperate (20 degrees C, 60% RH), hot dry (32 degrees C, 40% RH) and hot humid (32 degrees C, 90% RH). At 18 weeks each group was divided into 3 and re-allocated to 3 similar air-conditioned laying rooms as during the growing period. Different diets were fed to the 3 groups up to 18 weeks. The energy needed in order to produce the same average live body weight at 18 weeks was similar in all the 3 climatic chambers. The effect of treatments in the growing period was not significantly different (P > 0.05) for most of the parameters subsequently measured during the laying period. The exception was the body weight gain between 18 and 38 weeks and the food and energy intakes. However, apart from the sexual maturity, all these parameters were negatively influenced (P < 0.05) by the effect of hot climates during the laying period irrespective of method of rearing. The results of this study seem to indicate that ambient temperature experienced during the first 18 weeks after hatching has little effect on subsequent productivity and that rearing birds at high ambient temperature does not acclimatise them to these conditions better than rearing them under temperate conditions.