Abstract
The study was conducted in Hatchery -private sector- in Qushtapa, Erbil, from 24-5-2016 to 14-6-2016. The hatched chicks were reared from(14/6/2016 to 26/7/2016) in one of the halls of Department of Animal Production in College of Agriculture/ Salahadding University-Erbil within total 63 days. This study was conducted to investigate the effect of thermal manipulation (TM) during different embryogenesis stages of broiler breeder eggs as at embryonic days (ED): T2 (1-5), T3 (19-21) and T1 was control (no TM) on hatching results and subsequent chick characteristics and broiler productive performance of thermally conditioned chicks (exposed to 38.0 ± 2 °C for 12 hours/day) at 21st day of age. One thousand eight hundred (1800) Ross-308 eggs from twenty seventh weeks old imported were used. Eggs were randomly divided into three treatments with four replicates per each treatment (600 eggs/ treatment). Two identical incubators were used. In the first incubator all eggs were incubated at 37.7 ºC and 60-65% relative humidity (RH). The eggs thermally treated were transferred into the second incubator and was kept at 38.2 ˚C and 60-65% RH. After four (4) hours (hrs.) of thermal treating, the eggs were returned to the first incubator, immediately. It was found that thermal manipulation did not affect the hatchability percentage of total and fertile set eggs, normal bird’s percentage, and chicks’ quality. Post-hatching, 270 day-old chicks were randomly assigned according to treatment groups within hatching process. Chicks were distributed into three treatments with three replicates-groups-, with thirty chicks per each replicate. All treatment groups were subjected to thermal conditioning of 38 ±2 °C for 12 hrs. /day for a week, from day 21stpost-hatching. After exposure body temperature of birds were measured. Live body weight, bodyweight gain, feed consumption, feed conversion ratio and mortality were recorded on weekly basis. Production index, dressing percentage and carcass cuts percentages were measured at 35 and 42 days of age of broiler chicks. The overall data showed the following results: 1- T2 showed significantly (p≤0.05) higher relative growth than control group and T3. 2- T3 and control group showed significantly higher feed conversion ratio than T2, so T2 had a better cumulative ratio. 3- T2 and T3 showed significantly (p≤0.05) lower rectal temperature than control group. 4- T2 had the higher production index than T3 and control group at marketing age of 35 days. 5- Control group showed significantly lowest cumulative mortality percentage than T2. In the embryogenesisdevelopment, the incubation temperature is increased by 0.5°C for 4 hrs. This thermal treatment of the body temperature leads to decrease of the chicks’ temperature at day 42, as compared with the control group. As a result it confirms the acquisition of thermo tolerance in thermally manipulated groups.
