ammonia nitrogen added to diets deficient in dispensable amino acid nitrogen is poorly utilized for urea production in growing pigs background including ammonia in lowcrude protein cp diets deficient in dispensable amino acid daas increases nitrogen retention in growing pigsobjective we investigated the absorption and metabolism of dietary ammonia nitrogen in the portaldrained viscera pdv and liver of pigs fed a diet deficient in daa nitrogenmethods eight pigs with an initial mean sd body weight bw of 265 14 kg were surgically fitted with 4 catheters each portal hepatic and mesenteric veins and carotid artery the pigs were fed 28 191 kcalkg bw060 for 7 d and every 8 h a diet deficient in daa nitrogen supplemented with increasing amounts of ammonia nitrogen cp 776 927 and 1077 indispensable amino acid nitrogentotal nitrogen ratio 071 059 and 050 for control and low and highammonia diets respectively the treatment sequence was based on a latin square design with 3 consecutive periods on the last day of each period blood flows in the portal and hepatic veins were determined with a continuous infusion of amino hippuric acid into the mesenteric vein serial blood samples were taken to determine ammonia and urea nitrogen concentration net balances of ammonia and urea nitrogen were calculated for the pdv and liverresults cumulative 8 h ammonia nitrogen appearance in the portal vein increased p 005 with ammonia intake 433 958 and 1629 60 mg ammonia nitrogenmeal for control and low and highammonia diets respectively the cumulative hepatic uptake of ammonia nitrogen increased p 005 with ammonia nitrogen supply the cumulative urea nitrogen appearance in the hepatic vein tended to increase p 010 only in highammonia treatment 925 594 and 2097 92 mg urea nitrogenmeal for control and low and highammonia diets respectively and relative to the control diet represented 60 and 11 of ammonia nitrogen intakeconclusion dietary ammonia nitrogen is poorly utilized for urea production across splanchnic organs when pigs are fed diets deficient in daa nitrogen