Intestinal hyperammonaemia in horses

Abstract

Summary Intestinal hyperammonaemia in horses is a syndrome putatively caused by increased intestinal production and/or absorption of ammonia that clinically manifests as severe neurological abnormalities often in conjunction with signs of gastrointestinal dysfunction but without evidence of hepatic compromise. Ingestion of Black Locust (Robinia pseudoacacia) is a novel primary condition that may predispose to development of the syndrome as described in this issue. Treatment of the condition is symptomatic and aimed at decreasing blood ammonium concentrations by reducing further production and absorption, reducing brain oedema and preventing self‐inflicted trauma. Prognosis for survival is guarded, particularly in cases with severe gastrointestinal lesions, and is influenced by the ability to control clinical signs.

Metabolic disorders in foals

“…In this issue, Unt et al (2012) present a case of intestinal hyperammonaemia in a foal. This condition has recently been reviewed in this journal (Dunkel 2010).…”

“…Staphylococci and Enterococci, 2 of the bacteria that have been implicated in human ammonium production (Burne and Chen 2000), are not present in large numbers in the first few days of life (Kuhl et al 2011). Therefore the second proposed mechanism of intestinal ammonium production, deamination of glutamine by phosphate-activated glutaminase located in villus enterocytes of the small intestine (Romero-Gomez et al 2009;Dunkel 2010), could be responsible for intestinal ammonia production in foals. That said, the case reported by Unt et al (2012) and 3 additional foals aged <1 month reported by Dunkel et al (2011) had a primary diagnosis of colitis or enterocolitis, suggesting that the large intestinal flora may have changed considerably.…”

“…Two sources of ammonium from the intestine have been described (Dunkel 2010). The first is from the bacterial breakdown of urea, amino acids and proteins in the large intestine.…”

“…Therefore the second proposed mechanism of intestinal ammonium production, deamination of glutamine by phosphate‐activated glutaminase located in villus enterocytes of the small intestine (Romero‐Gomez et al . 2009; Dunkel 2010), could be responsible for intestinal ammonia production in foals. That said, the case reported by Unt et al .…”