Effects of increased diet density through increased dietary fat level on energy balance characteristics of broilers during the first week of life

The current study aimed to determine the effect of increased diet density through increasing dietary fat level on growth performance and energy balance characteristics of broiler chickens during the first week of life. The effects of diet density on energy and nitrogen metabolism were studied using a dose response design that comprised 5 dietary fat inclusion levels (3.5, 7.0, 10.5, 14.0, and 17.0%) while maintaining a constant digestible amino acid to energy ratio. Chickens were housed in open circuit climate respiration chambers. Preplanned contrasts were used to determine significant linear and quadratic relationships with diet density. Feed intake and BW gain linearly decreased and gain to feed ratio increased (P<0.001) with increasing dietary density. Nutrient efficiencies (calculated as gain per unit of nutrient consumed) for fat, nitrogen and gross energy linearly decreased (P<0.001). A linear decrease in heat production and the respiratory exchange ratio (CO2/O2) were found with increasing diet density (P<0.001). Protein intake and total energy, fat and protein retention were not affected by diet density. To conclude: increased diet density during the first week of age resulted in improved feed efficiency, but not nutrient efficiency. Protein and fat deposition in the body of broilers was similar.