Influence of thermal manipulation during embryonic development on hatchability traits and secondary sex ratio of broiler chicks

The current study was conducted to investigate the influence of thermal manipulation (TM) during embryogenesis on hatchability traits, secondary sex ratio and hatchling weights of broiler chicks. A total of 1200 fertile eggs obtained from Cobb-500 breeder broilers parent stock were used in this study. The eggs were randomly distributed into 4 experimental groups. Incubation conditions from day 1 to day 18 were 37.5°C and 52% relative humidity for control group (TM0). while incubation temperature of the thermally treated groups during 13-15 days of incubation was increased to 39oC for 2 hours in the second group (TM2), 4 hours in the third group (TM4) and 6 hours in the fourth group (TM6). At hatch, the hatchability traits and embryonic mortality (EM) were calculated; all hatched chicks were sorted, sexed and individually weighed. The obtained results showed that, Thermal manipulation did not adversely affect hatchability and embryonic mortality rate, but there was a positive significant effect on the normality of hatched chicks. However there were non-significant differences in the secondary sex ratio of hatched chicks. Thermal treatment did not significantly effect on body weight of hatching chicks.