Abstract
Three female sheep fitted with two T-shape cannulae in the upper small intestine were used for studying phosphorus absorption. They were fed alfalfa-timothy hay and a mixed concentrate diet at the level of 2% of body weight. The absorption study was conducted using temporarily isolated small intestine. Three different levels of phosphorus solution (10, 25 and 50mmol/l) were perfused at 10ml/min from the upper cannula and the concentrations of electrolytes in the drainage from the lower cannula were measured to determine absorption rates and efficiencies of electrolytes. The phosphorus absorption rate was increased with increasing phosphorus concentration in perfusate, i. e. the absorption rates were 46.6μmol/min and 112.2μmol/min in 10mmol/l and 50mmol/l of phosphorus concentration of perfusate, respectively. The efficiency of phosphorus absorption showed a significant reduction from 45.2% in 10mmol/l phosphorus in perfusate to 22.4% in 50mmol/l phosphorus in perfusate. The results suggest that phosphorus absorption from the small intestine depends on a phosphorus concentration in liquid phase digesta.
