In order to study of the effects of methenamin on hematological and biochemical parameters of broiler chickens, 58 day-old broiler chickens of Arian breed randomly divided to six unequal groups as follows: Group I: no use of methenarnin (n=10), group II: daily use of 1/1000 methenamin in drinking water for one week at the end of rearing period (n=8), group III: daily use of 2/1000 methenamin in drinking water for one week at the end of rearing period (n=8), group IV: daily use of 1/1000 methenamin drinking water continiously for 8 weeks (n=10), group V: daily use of 2/1000 methenamin in drinking water continiously for 8 weeks (n=12). group VI: daily use of 4/1000 methenamin in drinking water continiously for 8 weeks (n=10). The results revealed that after the administration of different dosages of methenamin, the number of white blood cells and the percentage and absolute number of heterophils significantly decreased (P<0.05). However, the percentage and absolute number of lymphocytes increased significantly (P<0.05). Following the administration of different dosages of methenamin, there was no significant difference in any of the biochemical parameters. This study showed that the administration of methenarnin can have not profound effects on hematological and serum biochemical parameters of broiler chickens.
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