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The role of dietary fatty acids and their subsequent effects on metabolism has received considerable attention in mammalian species. It is becoming increasingly clear that fatty acids have metabolic roles over and above their influence on energy density of the diet. Recent studies have linked changes in the fatty acyl composition of the plasma membrane, induced by the dietary fat profile, to alterations in both lipid and glucose metabolism. These dietary induced changes have profound effects on insulin action, glucose transport and enzyme activity that regulate triglyceride and fatty acid synthesis, factors that ultimately influence protein and lipid deposition of animals. Because of their high growth rate, broiler chickens have a high requirement for energy and the use of triglycerides as a major energy source has resulted in a fat carcass. A change in the glucose-insulin balance has been suggested as being the main reason for differences in adiposity between broilers selected for fatness or leanness. The hypotheses of this thesis is based on the finding that dietary polyunsaturated fatty acids (PUFA�s) increase the sensitivity of muscle tissue to insulin and this would presumably augment insulin-stimulated glucose uptake into muscle cells. Therefore, increasing the capacity of broiler muscle tissue to utilise glucose as its principal energy substrate would reduce the bird�s reliance on triglycerides and this inturn would result in a leaner carcass. The aims of this study are firstly to explore the role that dietary PUFA�s from the n-3 and n-6 series have on the growth and body composition of broiler chickens and secondly to determine the relationships between dietary fatty acid profile, tissue insulin sensitivity and lipid deposition. Because dietary fatty acids have been implicated in the modulation of hormones important for the growth and development of animals, a third aim of this thesis is to determine the effects of dietary n-3 and n-6 polyunsaturated fatty acids on pituitary and adrenal sensitivity. Since the modulation of metabolism by dietary fatty acids has been attributed to changes in the fatty acyl composition of the plasma membrane, the final aim of this study will be to investigate and characterise the molecular species of the breast muscle choline and ethanolamine phospholipids. Feeding either fish oil a source of n-3 PUFA�s or sunflower oil a source of n-6 PUFA�s fatty acids to broiler chickens resulted in a significant (P |
