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This thesis contains 86 publications on the general subject of the regulation of metabolism and performance in poultry by nutrients, mainly lipids and vitamins, and related biochemical and genetic interactions. There are 6 sections: 1) fat nutrition, 2) body fatness, 3) fatty liver and kidney syndrome, 4) vitamin nutrition and biochemistry, 5) bone biology, 6) sodium nutrition. Section 1 describes the effects of saturated fatty acids in impairing mineral absorption in young chickens, fat utilisation and requirements in turkeys and the role of unsaturated fatty acids in enhancing egg weight in laying hens. It is concluded in these last studies that egg weight is increased by a novel mechanism involving stimulation of oviduct protein synthesis. The problem of excessive fatness in broiler chickens is addressed in Section 2. The studies show how body fatness during growth is related to plasma very low density liprotein (VLDL) concentration and the use of this criterion in a 10-year divergent selection programme to breed lines of lean and fat broilers. Nutritional responses in the lines are compared and the bases of improved leanness and more efficient nutrient utilisation are related to differences in amino acid and lipid metabolism. The differences in immature body composition are shown to persist to maturity and the poorer reproductive performance of the fat line is shown to be associated with extremely high plasma oestrogen levels. It is concluded that genetically leaner broilers are metabolically and reproductively more efficient. The studies identify the practical procedures which have allowed the VLDL method to be applied in industry for the selection of more efficient broilers and turkeys. |
