| In order to discuss the effects of thermal acclimation during early rearing chick on adaptability acquisition in broilers exposure to heat, the production performance and some biochemistry index of Arbor Acres broiler were studied in this research, such as biochemical index, incretion, anti-oxidative enzyme, total white blood cell count, H/L value, changes of heat-shock protein 70 in the blood serum and liver, and so on. The results as follow:Firstly, in the single-factor tests, four hundreds 0-day-old Arbor Acres broilers were randomly allocated in four groups (including 4 replicates of 25 birds), and were bred in four cabins which thermal temperature in 3-5 day was controlled at 32℃, 32℃-35℃-32℃, 32℃-38℃-32℃, 32℃-41℃-32℃, respectively. Body weight, feed consumption and rectal temperature were measured when the thermal temperature experiment began and finished. The blood serum and liver sample should be collected at AM7:00 in 6 day, which was used to measure the content of incretion and HSP70 in experiment broilers. Then the temperature and humidity of four cabins were kept in line. The experiment finished on 35-day-old, and the body weight, feed consumption and rectal temperature were also measured at every week. On the other hand, total white blood cell count and H/L value were measured in 21, 28 and 35 days. The results showed that: The range test of chicken rectal temperature in 32℃,35℃,38℃,41℃groups were respectively 1.53℃,1.52℃,1.35℃,1.25℃, which indicated that the thermal acclimation temperature was higher, the chicken rectal temperature was more constant.Secondly,in a 4×2 randomized bifactor tests, 144 43-day-old chickens four thermal acclimation groups with 36 birds per group in experiment one were randomly allocated into 12 groups, and reared in four cabins which temperature was controlled at 22±2℃and 35±2℃(6 groups in two cabins with the same heat stress ). After three hours, blood samples were collected to measure biochemical index, incretion, anti-oxidative enzyme and HSP70 concentration. Then the chickens were slaughtered for liver sample to measure HSP70 concentration. The results showed that: 1.After the three hours acute heat stress with 35±2℃, the uric acid concentration in blood serum was significant (p<0.01) higher than control group. But the activity of super-oxide dismutase(SOD) significantly(p<0.05)decreased. This indicated that the non-enzymatic anti-oxidative system may play an important role in the anti-oxidative process. 2. There was significant or near to significant(p<0.05 and p=0.073)interaction function to serum HDL and CHO concentration between thermal acclimation during early rearing chick and acute heat stress during late growth stage. The serum HDL and CHO concentration was highest in 35℃acclimation group under 35℃acute heat stress condition, which indicated that broilers which thermal temperature in 3-5 day was controlled at 35℃can adapt better to 35℃acute heat stress.Thirdly, in a 4×2 randomized factor tests, 192 37-day-old Arbor Acres broilers which from four thermal acclimation groups with 48 birds per group in experiment one were randomly allocated into 12 groups, reared in four cabins which temperature was controlled at 22±2℃and 22±2℃to 35±2℃(6 groups in two cabins with the same heat stress ). The experiment continues for six days, and the body weight and feed consumption should be measured at day 37 and day 42. The temperature of comb, head and neck, chest and abdomen, leg and shank, wing and back and rectal were also measured during heat stress treatment. In 42 day, blood samples were collected to measure biochemical index, total white blood cell count, H/L value incretion, anti-oxidative enzyme and HSP70 concentration. Then the chickens were slaughtered for liver sample to measure HSP70 concentration. The results showed that:1.Under the chronic heat stress condition, the loss of performance and increase of body temperature in the 35℃and 38℃acclimation group were lower, but the decrease of TG, increase of HDL and total white blood cell count were higher than other groups. this indicated that broilers which thermal temperature in 3-5 day was controlled at 35℃and 38℃may enhance the adaptive ability under chronic heat stress condition during late growth stage . 2. Under the chronic heat stress condition, the serum and liver HSP70 concentration in circulation heat stress group were significant(p<0.05)lower than that in chronic heat stress group, which may be caused by cell damage in chronic heat stress. The other reason may be that the new thermal acclimation response was induced by intermission increase of environment temperature. On the other hand, the serum GLU and CHO in circulation heat stress group were also significant or near to significant (p<0.05 and p=0.063) higher than that in chronic heat stress group, which indicated that adaptive ability of broilers can be achieved by circulation heat stress.In onclusion, broilers which thermal temperature in 3-5 day was controlled at 35℃and 38℃may enhance the adaptive ability under heat stress condition during late growth stage considering all of the experiments and the advance...
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