الفهرس 
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Abstract
The present study aimed to investigate the histopathological aspects, growth performance, urea residue in muscle and liver of broiler birds and chemical composition of the breast muscles of chicks fed graded levels of urea treated ration. Eighty, day old broiler chicks (avian48) were reared for 6 weeks. Water and feed were available ad libitum. Chicks were housed in clean well ventilated room and hygienic measures were done during the whole period of the experiment. After one week of age, chicks were randomly divided into 4 equal groups (I, II, III and IV), twenty chicks in each. Four types of ration were formulated by adding urea in percentage of 1.25% (group I), 2.5% (group II) and 5.0% (group III), while the birds of group IV served as control. Five birds from each group were sacrificed at the day 7, 14, 28 and 35 from adding urea. At the end of the experiment 5 samples from the breast muscle, liver of each group birds were obtained for tissue residue analysis and chemical meat composition. The most predominant clinical signs were respiratory symptoms, watery diarrhea and staggering gait. Body weight and feed consumption were increase in group I and II, while group III showed mild decrease. Moreover, there was difference in the FCR between the urea treated groups and control at the end of the experiment. The tissue residue in muscle and liver showed high significant value in group III when comparing with the other groups. The chemical composition of the muscle showed that the moisture content in group III was high than group IV. There was non-significant increase in the crude protein level in group II. There was significant increase in ash percent in group II. The fat content in the muscle of all urea treated groups was significant decrease than IV group.
Grossly, the kidneys were enlarged and pale in color with dark red areas of hemorrhages on the surface. Occasionally, the ureters of chicks fed 5%urea were distended with urates. The livers were swollen, congested or mottled with rounded borders and distended gall bladder. Occasionally, the liver was yellow in color and exhibited minute necrotic foci on cut section. The lungs were congested and edematous or dark brown in color. The brains were slightly hyperemic and the breast muscles were congested with occasional petechial or linear hemorrhage on the surface. These lesions were more pronounced in group II and III.