Effect of heat stress for specific period on juvenile traits, feed efficiency and some heat stress parameters in different genetic groups of broilers
 

To evaluate the effect of heat stress an experiment was conducted in which one cross (PB-1X Naked neck), two pure lines ( PB-1 and Naked neck) and corresponding control populations were generated simultaneously on the same day.120 chicks in PB-1X Naked neck  (Control 120), 91 chicks in Naked neck pure( Control 82) and 81 chicks in PB-1 pure ( Control 80)were generated. Temperatures were raised (up to 40°C) by providing the two halogen lamps in each of the heat stressed genetic groups from 4-6 weeks of age. Body weights were recorded at 0, 2,4, 6 and 7 weeks of age along with conformational traits like breast angle and shank length at 6 weeks of age. 2ml of blood was collected at 6weeks of age from all the 6 genetic groups (10 birds from each) to estimate the heat stress parameters. Feed efficiency was recorded at 6 weeks and 7 weeks of age. Significant differences were found for SOD, CAT, ALP and GPx between heat stressed and control genetic groups. Higher estimates were found in heat stressed genetic groups as compared to corresponding control groups. For juvenile body weights in stressful conditions there is significant difference between genetic groups. Lower juvenile body weights were recorded in heat stressed genetic groups as compared to control groups. Lower feed efficiency was recorded in heat stressed genetic groups as compared to corresponding control groups.