Effect Of Thermal Acclimation In Later Hatching Stage On Thermotolerance Of Broiler

The two thesises studied on the effect of early age thermal acclimation on the hatching in hatching period and on thermotolorence in later growing stage. The experiment one of experimental thermal acclimation studied on the hatchability, the weight and body temperature of chickens in hatching period. The experiment two of experimental thermal acclimation studied on the effect on thermotolerance of broilers in later growth stage.The first trial was designed as a single factorial experiment, the eggs were treated with different temperature(38.2℃, 38.6℃, 39.0℃) for there hours every day when those were hatched 16d～18d. The hatchability and healthy rate, the weight and body temperature of different treatments have been evaluated .The cockerel in the second trial come from the first one were thermal challenged at 35d～42d in broiler. The performance, physiological and biochemical parameters of blood, index of viscera organs and immune organs, anti-oxidation, body temperature and other parameters of broiler were measured .The following are the results:1. The results show: Compared with the control group, the hatching rate and healthy rate of experimental group increased by 1.43%, 2.18%, 1.48% and 1.54%, 2.24%, 2.89%. The weight of embryo at the end of thermal acclimation and the weight of day-old broiler have no significant difference between the control group and experimental group (P＞0.05) , but compared with the control group in the experimental group showed significantly elevated rectal temperature (P＜0.01).2. The results show: The mortality of the control is 20.63%, but the mortality of experimental group decreased by 29.91%, 40.43% and 48.42% throughout the growing period. It has no significant difference in the ADG between the experimental group and control group before thermal-challenged. The ADG of the control group was lower than that of the experimantal group in late growing stage. It has difference in water intake between the experimental and control group, no difference during early thermal-challenged (P＞0.05) , but during the late thermal-challenged the control group was significant lower than the experimental group (P＜0.05) . The rectal temperature of control group was significantly lower than that of experimental group at 0～7 day-old (P＜0.05), but the rectal temperature has no difference between the control group and the experimental group at 9 day-old. During the thermal-challenged the rectal temperature was up in the 24th hour of thermal challenged, but after the 72th hour decreased, and then tends to be stable. The rectal temperature and surface temperature of the experimental groups are higher than that of control group after 24h of thermal challenged, Respiration rate of the control group has no significant difference with the experimental group (P＜0.05). The T3 and T4 of serum has lower level than control groups (P＞0.05) . The level of SOD of experimental group was higher than that of control group, but the level of MDA of control group was higher than that of experimental group (P＜0.01). The level of TP, ALB (P＞0.05) and GLOB (P＜0.05) of experimental group are higher than that of control group. The level of GLU, BUN and TG of control group are higher than that of experimental group. It has no difference in GOT and CK between control group and experimental group. Organ index from 35d to 42d of the control group and experimental group has no significant difference (P＞0.05) .The following conclutions can be drawn from all the above results:1.It has no significant effect of thermal acclimation in later hatching stage on the hatchability and heathy rate (P＞0.05) in the trial, but has significant effect on the time of hatching. It has no significant effect on the weight of day-old chickens (P＞0.05) , but it has raised the rectal temperature (P＜0.05).2. Thermal acclimation can increase performance of broiler and the therotolerance of broiler at the late growth stage. Thermal acclimation can reduce serum thyroid hormone levels to reduce heat production and can effect physiological and biochemical indicators of the body respond effectively to enhance thermotolerance. Early age thermal acclimation can increase the antioxidant capacity of the body tissues and organs, and reduce heat stress injury of tissues and organs, raise the body heat resistance. Early age thermal acclimation can increase the body's core temperature, enhance the effective heat capacity of the surface. Early age thermal acclimation can change body temperature balance and increase core temperature of the chicken.3.Consider the effect of thermal acllimation in late hatching stage on the hatvhability, heathy rate, production performance and other aspects,in this experiment ,the temperature 38.6℃～39.0℃and the duration 3h/d of thermal acclimation at 16～18 age of embryo is more appropriate.