Plasma citrulline, arginine, nitric oxide, and blood ammonia levels in neonatal calves with acute diarrhea

Gultekin, Mehmet; Voyvoda, Huseyin; Ural, Kerem; Erdogan, Hasan; Balikci, Canberk; Gultekin, Gamze

Ammonia is a toxic compound to many organ systems, especially the brain. Excessive blood ammonia concentration might result in respiratory alkalosis, cerebral edema, mental disorders, seizures, coma, and death. Increases in blood ammonia concentration are generally considered to only be a result of liver-related disorders, but other underlying causes should be assessed as well. 20 High blood ammonia levels can develop from several different mechanisms, including (1) hepatic insufficiency, (2) reduced activity of urea cycle enzymes, (3) metabolic disorders of organic acids, and (4) portosystemic shunt. 20 In the present study, blood ammonia concentration with a median of 59.8 μmol/L in diarrheic calves was significantly higher than that in healthy calves (Table 2 ). Although these median levels remained within the reference range (<90 μmol/L) reported for cattle, 40 median blood ammonia levels in the severe diarrhea (105.7 μmol/L), severe dehydration (113.9 μmol/L), and SIRS positive (105.7 μmol/L) subgroups were above the reference limits ( Figures 2D, 3D, and 4D ). This increase in these subgroups can be considered to be hyperammonemia and might be related to the loss of liver or kidney function because of circulatory failure in the result of diarrhea, as well as the decrease of plasma citrulline and arginine concentrations which decreases the efficiency of the urea cycle. In this content, hyperammonemia has also been reported in a human case of short bowel syndrome along with decreased concentrations of arginine and citrulline 54 and in systemic infections with bacteria or virus. 55 The moderate and positive relationship of blood ammonia with SIRS status (Table 3 ) and the effects of severity of diarrhea and degree of dehydration) might be based on the factors affecting urea cycle and ammonia metabolism. 20 The results of this study are subject to some limitations. This study included a variety of mono or combined causative agents (Table 1) with NCD in calves with noninfectious diarrhea cannot be determined because only the antigens of the most common enteropathogens in feces were evaluated. Additionally, the duration of disease is a confounding factor which could cause difficulty in diagnosis of noninfectious diarrhea. Lastly, the sample size of this study was small, especially in neonatal calves with noninfectious diarrhea.