Metabolic Programming Induced By Glucocorticoids In Broiler Chickens

Several trials were conducted to investigate the effects of metabolic programming induced by glucocorticoids on the growth and metabolism of broiler chickens. We used exogenous glucocorticoids to induce stress in the embryo stage and the early period and studied the effects of metabolic programming on performance, tissues development, physiology and bioche- mistry parameters and metabolism in broiler chickens.In trial 1 of chapter 2, the experiment was conducted to investigate the possible effect of corticosterone treatment at different hatching time on the development of chicken embryos. Seven hundreds of AA broiler eggs were divided into 7 groups and randomly subjected to one of the seven treatments, corticosterone treatment (200ng) at E0, E7 and E14 in yolk sac, three positive control groups that injected with corn oil at E0, E7 and E14, and one negative control group. In trial 2, the experiment was conducted to investigate the possible effect of corticosterone treatment at different dose and different post on the development of chicken embryos. Six hundreds of AA broiler eggs were divided into 6 groups as negative group, positive 1 group, positive2 group, the treatment of 60ng and 200ng corticosterone in air chamber, and the treatment of 60ng in yolk sac. In trial 3, the experiments were conducted to investigate the possible effect of glucocorticoids treatment at E18 on the development of chicken embryos in order to study the effect of metabolic programming. Firstly, five hundreds and twenty AA broiler eggs were divided into 3 groups as negative control group (EN), positive control group (EO), the treatment of 60ng cort in air chamber at E18. Secondly, four hundreds and twenty AA broiler eggs were divided into 3 groups as negative group, positive group, the treatment of 65μg dex in air chamber at E18. The incubation time, hatching ability and posthatching body weight were recorded. The blood samples were collected and the organ weights were measured after hatching.The results indicated that 200ng corticosterone treatment in air chamber at E18 to the positive control group significantly reduced hatching ability, shorted the incubation time, decreased the rate of posthatching weight and restrained the development of heart and liver, the concentration of UA increased. 60ng corticosterone treatment in yolk sac at E7 to the control group shorted the incubation time, reduced hatching ability, and decreased the concentration of Glu. Corticosterone treatment at E0 significantly reduced hatchingability and increased mortality rate. Corticosterone treatment at E7 shortened the incubation time and tended to reduce the hatchingability. The development of heart, liver and thigh muscles were restrained by corticosterone treatment. The result showed that the effect of corticosterone on the development of chicken embryo was age dependent. Moreover, the effect of injection had an adverse effect on embryos as well. 60ng corticosterone treatment at E18 did not significantly reflect the hatching, but 65μg dex treatment destroyed the normal metabolism.In chapter 3, the experiments were conducted to investigate the possible effect of glucocorticoids by 65μg dex and 60ng corticosterone treatment at E18 on the later growth of chicken broilers and suffered with cold and heat stress at 7d and 42d in order to study the effect of metabolic programming. The results indicated that dex treatment in air chamber at E18 significantly restrained the growth of 7d broilers and decreased the rate of bursa, reduced the immunity function. The treatment of dex at E18 induced the cold tolerance of 7d broilers but the mechanism was unclear. The 60ng Cort treatment in air chamber at E18 has no effect on the growth and organs development of broilers, but increased the rate of liver, restrained the the two weeks mebabolism of protein,increased the fat synthesis in the early days.The treatment of cort at E18 restrained the increase of temperature of heat stress at 42d but whether induced the heat tolerance need to study nextly.In chapter 4, the experiments were conducted to investigate the possible effect of stress experience by dex treatment at 3-5d on growth performance, insulin sensitivity and heat tolerance in broiler chickens. The results indicated that stress experience resulted in a reduction in growth rate in early stage, but after that the broilers experienced stress resulted in compensatory growth, increased the fat deposition. High-energy diet reduced the insulin sensitivity and resulted in insulin resistance of 7d broilers. Stress experience resulted in reduction of insulin sensitivity of 21d broilers, increased the concentration of empty insulin of 42d broilers and reduced the insulin sensitivity. Stress experi -ence in early stage had no effect on metabolism and heat tolerance of 42d broilers with heat stress. Maybe the effect of glucocorticoids is different with feed restriction on heat tolerance at market age.