RESPONSE OF COMMERCIAL LAYERS TO HOUSING AT DIFFERENT CAGE DENSITIES AND HEAT STRESS CONDITIONS. 1- PHYSIOLOGICAL INDICATORS AND IMMUNE RESPONSE

An experiment was conducted to determine the effects of heat stress and different cage densities on blood indices and Immune response. The hypothesis that, commercial layers, caged at lower densities, react less intensely, to heat stress, than would the hens caged at higher densities was also tested. A total of 936, Lohman Selected Leghorn (LSL) hens, fifty eight weeks old, were used in this experiment. These hens were originally housed, at eighteen weeks of age, as follows: 1-The first group (468 hens) was housed in a conventional open-sided house (Heat Stressed). 2-The second group (468 hens) was housed in a conventional open-sided house with desert cooling systems (Control). Pullets were placed at 4, 5, 6, 7, 8 and 9 birds per cage in wire cages (60 cm wide by 50 cm deep and 40 cm height). At 58 weeks of age, the first group was exposed to high environmental temperatures, ranging from 40-42 O C and 65-70% relative humidity (five hours daily for seven consecutive days). After each daily heat exposure, the hens were exposed to the normal ambient temperature of the season (20-26 O C and 60-65% relative humidity). The control group was exposed to the ambient temperatures of the season, ranging from 20-26 O C and 60-65% relative humidity. Data were collected during the period of heat stress exposure .