ABSTRACT The present study was carried out to evaluate the effects of pyrimidine nucleosides on growth, intestinal morphology, digestive enzymes and humoral immunity in broilers from 0 to 21 days of age. A total number of 360 day old chicks (Cobb 500) was randomly divided into 4 treatments with 6 replications. Treatments were comprised of a corn-soybean meal based control diet and diets containing 0.1% pure cytidine, 0.1% pure uridine and 0.1% equal amounts of pure cytidine (0.05%) and uridine (0.05%). On days 11 and 21, two birds per cage (12 birds per treatment) were euthanized to obtain samples of serum, intestine, bursa and spleen. The combination of cytidine plus uridine increased (P < 0.05) body weight and average daily gain of broilers. Supplementing cytidine plus uridine increased (P < 0.05) villus height and width along with activities of alkaline phosphatase and aminopeptidase; however, maltase was not affected by the experimental diets. The combination of cytidine and uridine increased (P < 0.05) the relative weight of the bursa of Fabricius and IgA activity in the jejunum, but there was no significant difference among treatments regarding the relative weight of the spleen. In conclusion, the study clearly indicated that the combination of cytidine and uridine could improve health status and performance of broilers.

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