Equine gastric ulcer syndrome in foals

Differences exist between the gastric mucosa in adults and foals. The squamous gastric epithelium increases in cell depth and keratinisation over the first few weeks of life (Murray and Mahaffey, 1993). This is thought in part to be related to increasing exposure to gastric acid in addition to growth factors present in milk. The gastric pH level of neonatal foals is slightly higher than more mature individuals. The ventral gastric pH level of newborn foals is approximately 4 and decreases to a more adult type pH level of around 2 by 3 days of age (Baker, 1993). There is significant daily variation in the gastric pH level in healthy foals. Milk ingestion has an important alkalinising effect and the pH level drops during sleep (Sanchez et al, 1998). The typical pH range is between 0.8 and 6, but the majority of healthy foals have an acidic pH similar to adult values by a week of age. In contrast, sick neonates have different gastric pH profiles. Many sick neonates have a consistently alkaline pH (Sanchez et al, 2001). The ability to produce an acidic gastric pH seems to have an association with survival. In one study 77% of foals with a gastric pH less than 5 (even transiently) survived compared with only 20% of foals with alkaline pH (Sanchez et al, 2001).