Energy Partitioning and Tissue Respiratory Metabolism of Laying Chickens Reared under Summer Conditions of Egypt

A total number of 156 laying chickens at 29 weeks of age were used in the study. Birds were distributed equally in two dietary energy levels (2600 and 2900 Kcal ME/Kg feed) and three strains viz., Lohmann Selected Leghorn (LSL), Fayoumi and Dandarawi. Three experiments were conducted to measure energy partitioning values (36 birds), liver oxygen consumption and oxygen consumption of epithelium lining of magnum and shell gland (48 birds) and thermoregulation (72 birds). Dietary energy level had significant effect on apparent metabolizable energy (AME), the energy needed for maintenance and physiological work (MPWE) and liver oxygen consumption. Effect of dietary energy level was not significant on egg production performance, energy intake (EI), excreta energy (ExE), egg energy (EE) and physiological variables. Strain effect was significant on all energy partitioning variables, liver oxygen consumption, percent of change of cloacal temperature, skin temperature and egg production performance. The strain of higher production performance (LSL) had higher energy intake (EI), excreta energy (ExE), apparent metabolizable energy (AME), the energy needed for maintenance and physiological work (MPWE) and egg energy (EE). Dandarawi showed higher liver oxygen consumption, epithelium lining of magnum and shell gland. In addition, Dandarawi showed highest percent of change of cloacal temperature. It was concluded that Dandarawi and Fayoumi seemed to be energy wasting birds but with different models. H.M.S.Shoukry, et al.,