Effects Of Stress And Dietary Energy Level On Growth And Lipid Metabolism Of Broiler Chickens

Four experiments were conducted to investigate the effects of stress and dietary energy level on lipid metabolism of broilers.In trial 1 of chapter 1, broiler chickens fed two different energy level of diets were fed with corticosterone from 3d to 9d to induce chronic stress, in order to investigate the effects of chronic and high energy level on growth and lipid metabolism of broiler chickens. One hundred and forty four day-old male chickens were randomly assigned to four groups and each group had three pens of 12 birds. At 3 days of age, one half of the experimental chickens (6 pens) were provided with a high energy diet (HED, 3600 Kcal ME/kg) while another half of chicken were feeding with a isonitrogenic (20% CP) low energy diet (LED, 2610 Kcal ME/kg). In each dietary treatment, one of the two groups of chickens was randomly assigned to CORT administration (30mg/kg diet) and another group of chicken were fed with normal diet. At the end of 7-d experiment, neonatal chicekens were weighed, samples were obtained from 4 birds randomly selected from each replicate (12 bires each group) for determination. The results indicated that chronic stress significantly enhanced abdominal, cervical and groin fat weights (%) but significantly depressed breast and thigh muscle weights (%) with respect to body weight. Intaking of high energy diet significantly enhanced abdominal, cervical and groin fat weights but significantly decreased breast muscle weights (%).In trial 2, broiler chickens fed of two different levels of diets were fed with corticosterone from 28d to33d to induce chronic stress, in order to determine the effects of chronic and dietary energy level on growth and lipid metabolism of broiler chickens. One hundred and forty four 28-d old male chickens were randomly assigned to four groups and each group had three pens of 12 birds. One half of all the experimental chickens were provided with a high energy diet (HED, 3600 Kcal/kg) while another half of chicken consumed a isonitrogenic (19% CP) low energy diet (LED, 2800 Kcal/kg) (Table 1). At 34 d of age, 12 chickens with mean body weight were randomly selected from each group. At the end of 6-d experiment, neonatal chicekens were weighed, samples were obtained from 4 birds randomly selected from each replicate (12 bires each group) for determination. The results indicated that chronic stress significantly enhanced abdominal, cervical and groin fat weights (%) but significantly depressed breast muscle weights (%) with respect to body weight. Intaking of high energy diet significantly enhanced abdominal weights (%) but significantly depressed breast muscle weights (%).In chapter 2, broiler chickens fed low energy diet were fed with corticosterone from 3d to 8d to induce chronic stress, in order to explore glucose drinking and chronic stress on growth and lipid metabolism of broiler chickens. One hundred and forty four 3-d old male chickens were randomly assigned to four groups and each group had three pens of 12 birds. All the experimental chickens were feeding with a low energy diet (2800 kcal ME/kg, 20% CP) as the description in Experiment 1. One half of the experimental chickens (6 pens) were assigned to drink water supplemented with glucose (80g/L) (GLU) and another half of chicken were supplied with tap water supplemented with saccharin serving as control group (2g/L, SC). At 10 d of age, 12 chickens with mean body weight were randomly selected from each group. The results indicated that chronic stress significantly enhanced abdominal, cervical and groin fat weights (%) but significantly depressed breast and thigh muscle weights (%)with respect to body weight. Administration of glucose significantly enhanced abdominal, cervical and groin fat weights (%) but significantly depressed the breast muscle weights (%).In chapter 3, 34d old broiler chickens were injected insulin subcutaneously to explore the effects of insulin on lipid metabolism. Twenty 35d old broiler chickens of each group in trial 2 of chapter 1 were separately divided into two groups randomly, birds of each group were injected insulin (4u/Kg BW) and saline (0.25ml/Kg BW) separately. The blood samples and fat tissues were obtained after 3 hours of injection. The results indicated that high insulin level of blood plasma was induced by insulin-injection subcutaneously. High insulin level significantlly lower the blood plasma glucose and had no significant effects on blood plasma triglyceride, NEFA, VLDL.