Background: Ascites is a major cause of mortality and morbidity in modern broiler production. The aim of this study was to determine the effects of different levels of dietary Nucleotide Supplementation (NS) on pulmonary hypertension syndrome (also known as ascites syndrome, AS). Materials and methods: In the trial, 308 Ross 308 (mixed sex) broiler chickens were distributed in a completely randomized experimental design into 4 treatments with 7 replicates of 11 birds each. Experimental groups were defined by the inclusion of 0 (control), 0.5, 1 and 2 g/kg NS in the diets. Ascites was induced in broiler chickens by excess salt (receiving 0.2 % NaCl) in drinking water. Growth performance, mortality, blood parameters as well as ascites indices (right ventricle [RV], total ventricle [TV] weights, and RV/TV) were evaluated. Results: The results of this study showed that feed intake, body weight gain, feed conversion ratio of broilers were not affected by treatments (P> 0.05). Ascites-related mortality, plasma triiodothyronine (T3) concentrations were significantly decreased in treatment with 1 g/Kg nucleotide in diets (P<0.05). RV weight was significantly heavier and RV/TV ratios was significantly higher in treatment with 0 g/Kg nucleotide diets, and decreased in treatment with 1 g/Kg nucleotide in diets (P<0.05). Conclusion: Our findings showed that excess salt in drinking water induced pulmonary hypertension in broiler chickens. It is concluded that the inclusion of 1 g/kg nucleotide in susceptible broiler chicken diets has a systemic anti-hypertensive effect and could decrease ascites incidence.

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