Water absorption in relation to fermentation in the colon of the ostrich (Struthio camelus)

Abstract

The colon is a major site for fermentation and water absorption in the ostrich. Water absorption along the colon was evaluated and its relationship to osmolality, Na+ concentration, short chain fatty acid (SCFA) concentration and carbohydrate content of digesta analysed. Mean water content decreased from 5.30±0.99 to 2.51±0.13 ml/g dry mass in the first 5 m of the colon. Correspondingly, mean carbohydrate content fell from 529.85±46.61 to 434.99±29.89 mg/g dry mass. A significant correlation was shown between the decreases in mean carbohydrate and water content along the colon (r²=0.997, P<0.05). Changes in mean osmolality (±10 mOsm/kg) and SCFA concentration (±7 mmol/l) were minimal in comparison to the change in Na+ concentration (-54 mmol/l). These findings reflect a close coupling between SCFA production and absorption on the one hand and water absorption on the other.