The study was conducted in Hatchery -private sectorin 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 21 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 21post-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: 1T2 showed significantly (p≤0.05) higher relative growth than control group and T3. 2T3 and control group showed significantly higher feed conversion ratio than T2, so T2 had a better cumulative ratio. 3T2 and T3 showed significantly (p≤0.05) lower rectal temperature than control group. 4T2 had the higher production index than T3 and control group at marketing age of 35 days. نــيدـفارــلا ةـــعارز ةـــلـجـم ( دلجملا 47 ( ددعلا ) 2 ) 2019 ISSN: 2224 9796 (Online) ISSN: 1815 316 X (Print) Mesopotamia J. of Agric. Vol. (47) No. (2) 2019 150 5Control 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. Key-Words: Epigenetic adaption, Thermal manipulation, Early age heat conditioning, Performance, Thermo-tolerance. Received: 8/11/2018, Accepted: 16/5/2019 INTRODUCTION Poultry meat consumption is expected to be raised by 60% over the next 20 years and will be the most important meat category worldwide by 2030FAO (2010) Genetic selection strategies which has significantly Improved growth of meattype broiler chickens during recent decades, but lack of a parallel development of the visceral systems causes significant difficulties for broiler chickens in coping with high temperature challenges, due to the large body mass and high rate of metabolism associated with rapid growth Cangar,A.Z.et al., (2008).Thermotolerance can be defined as the ability of organisms to survive and overcome lethal thermal stress from a previous heat exposure Moseley,P.L.(1997). For Increasing the thermo-tolerance capacity of the birds and also inhibition of economic losses as a result of heat stress, the adaptation to ambient conditions depends on a mechanism called epigenetic adaptation when chicken can be better conditioned to thermal stress tolerance during the pre-hatching and early posthatching period through epigenetic mechanism by exploiting the immaturity of temperature regulation in embryos and early post-hatch birds by thermal conditioning at critical developmental phases Yahav,S.andJ. P.Mcmurtry(2001)and these methods have provided some suitable results for broiler industry Nickelmann, M. and B. Tzschentke(2002). Under these conditions there is a period when the thermo-tolerance can be enhanced by thermal conditioning, without impairing the performance Yahav,S.andS.Hurwitz(1996). MATERIALS AND METHODS The chicks of this experiment were exposed to thermal manipulation by increasing 0.5 ̊C from standard temperature for four hours daily during embryogenesis in early and late embryonic stages, the heat exposing on treatments were as follow: Heat exposing treatment started from ED (1-5) incubation periods and ED (19-21) of hatching period, respectively. While, T3: Control: no TM= exposed to standard conditions (37.7 °C and 65-70% RH) in incubator and (37.3, 37.1 and 37.0 °C during days 19th, 20th and 21st of hatching, respectively with 75-80% RH) in hatchery.Two hundred seventy (270) a day-old hatched chicks (Ross-308) reared in poultry research hall of Grdarasha farm/ Animal Resources Department/ College of Agriculture/ Salahaddin University from 14/6/2016 to 26/7/2016. The house was divided into 9 floor cages (2*1.7) m2. The chicks of both treatments and control groups were randomly divided into 3 replicates / group, three cages for each نــيدـفارــلا ةـــعارز ةـــلـجـم ( دلجملا 47 ( ددعلا ) 2 ) 2019 ISSN: 2224 9796 (Online) ISSN: 1815 316 X (Print) Mesopotamia J. of Agric. Vol. (47) No. (2) 2019 151 treatment. The chicks were reared at standard environment temperature till 21 day old, all chicks were exposed to heat conditioning of (38±2°C) from 21 days old for 12 hours/day for one week till 28 days old, after that the birds exposed to elevated temperature 26±2°C till marketing age. A constant photoperiod of 23L: 1D hours during period was provided. Feed and water were provided ad libitum along the experiment period. Birds were fed three rations; starter from (1-22) days, grower from (23-36) days and finisher from (36-42) days. The analyzed metabolic energy (ME kcal) and crude protein (CP %) for starter, grower and finisher was (2925 kcal, 22-23%),(3040 kcal, 20-21%) and (3100 kcal, 18-19%) respectively. Vaccination program used during the experiment was according to Intervet ScheringPlough Animal Health. The experiments were executed as a complete randomized design (CRD), all data analyzed using the SAS,Statisticalanalysissystem(2001). Duncan`s multiple range tests were used to compare differences among treatment means Duncan, D. B. (1955). RESULTS AND DISCUSSION Table (1) shows that T1 had significantly (P≤0.05) higher relative growth compared to T2 and control group. While T2 showed significantly (P≤0.05) lower relative growth than other thermally manipulated groups and the control group. According to Willemsen,H.;et al.,(2008) development during the first week of life of a chick was important to their future performance. Physiological processes such as cell hyperplasia and hypertrophy, maturation of the thermoregulatory and immunological systems, growth and differentiation of the gastrointestinal tract will subsequently markedly influence BW until market age. Table (2) shows that there were no significant differences in live body weight (BW) at day 35 and 42 of age. The non-significant differences in BW at 6th week were due to the changes of kinetics of satellite cell prolification which improved numerically BW at slaughter age. Further, in embryos as well as chicks of meattype poultry mild heat exposure if applied during developmental ‘Critical periods’ environmental influences can change the programming of respective body Functions Tzschentke,B.and A.Plagemann(2006). Accumulative BWG (1-35d) was noted that T1 was significantly (P≤0.05) lower than control group. The difference in weight gain among treated groups may be due to different environmental Conditions in the hatcher, chicks hatching at different moments within the hatch window are subjected to Different conditions for a variable length of time, which may lead to different chick physiology at hatch and at the typical moment of chick collection and also to different growth post-hatch Van deVen, L. (2012). Also the reduction in weight gain during and immediately after conditions to high temperatures may be due to that the chicken directs the energy used for its growth to maintain body temperature within normal range with minimal response to heat stress and ensuring the organic function of tissues within physiological Limits Lin,H.;et al.,(2006). As well as, high rearing temperature decrease in weight gain may due to that heat stress Increase serum corticosterone level (which stimulate much higher muscle breakdown, that contributed to the lower BWG observed in birds kept in heat stress than those in a thermoneutral نــيدـفارــلا ةـــعارز ةـــلـجـم ( دلجملا 47 ( ددعلا ) 2 ) 2019 ISSN: 2224 9796 (Online) ISSN: 1815 316 X (Print) Mesopotamia J. of Agric. Vol. (47) No. (2) 2019 152 environment Quinteiro-Filho,W.M.;et al.,(2010). In poultry it is believed that less weight gain in the heat stressed groups due to reduction in intestinal absorption efficiency was partly explained by decreased metabolic utilization of nutrients,Increased heat production, reduced protein retention, and enhanced lipid deposition Baziz,A.H.;et al.,(1996). Accumulative FI (1-35d) and (1-42d), T1 consumed significantly (P≤0.05) less feed than other treatment groups (Table 2). The most influential factors affecting feed consumption of chicks have been suggested to be related to the incubatio

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The effect of thermal manipulation of (ross 308) broiler breeder eggs during early & late embryogenesis stages on productive performance of hatchie chicks at heat stress condition.

I Ibrahim

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The effect of thermal manipulation of (ross 308) broiler breeder eggs during early & late embryogenesis stages on productive performance of hatchie chicks at heat stress condition.