Performance and some physiological indices of broiler chicks fed urea-containing grower diets

. Five experimental diets (of similar crude protein (18.9%) and metabolizable energy (about 3136 kcal/kg) contents] having five graded levels of urea (0.00, 0.345, 0.69, 1.035 and 1.38%) were formulated and used from 3 to 6 weeks of age. All birds had free access to feed and water and were reared under similar managerial and environmental conditions. The response of chicks to feeding the urea-containing diets included growth performance (in terms of feed intake (FI), live body weight (LBW), body weight gain (BWG), feed conversion (FC), economic efficiency of growth (EEG), mortality rate, nutrient digestibility (including dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), crude fiber (CF) and nitrogen-free extract, and ash and nitrogen retention], certain carcass traits, and some blood parameters. The obtained results could be summarized as follows: There were significant depressions in final LBW, BWG and FI of birds fed the urea-containing diets as compared to their control group; however, FC and EEG were not significantly affected. With the exception of slight reductions in crude protein digestibility and rate of nitrogen retention in birds fed the 1.38% urea in their diet while the other experimental groups (fed diets containing 0.345, 0.69 and 1.035% urea) exhibited means of digestibility for DM, OM, EE, CF and NFE as well as ash retention comparable to those of the control .birds. Feeding the urea-containing diets had no significant effects on either carcass traits or blood parameters but urea concentrations in blood plasma of broilers fed the diets containing 0.69, 1.035 and 1.38% urea were significantly higher compared with their control counterparts. Because of the depressed growth performance and poor economic efficiency of growth resulting from feeding the urea-containing diets, it can be concluded that urea addition as a source of non-protein nitrogen in broiler chick diets is nutritionally invaluable and not recommended.