1990 Volume 52 Issue 1 Pages 91-96
Effect of the osmolality on the absorption of water, electrolyte and VFAs from the isolated ruminoreticulum under normal feeding condition were investigated in a series of the studies to evaluate the rumen as a potential site of absorption in oral fluid therapy of adult cattle. Thirty of 40 l of the test solutions with varying osmotic pressure (100, 200, 300 and 500 mosmol/L, pH 6.8) were prepared using different concentrations of electrolytes and VFAs. These were infused into the isolated and emptied ruminoreticulum, and the absorption rate of water and each components were studied for 3 hrs. Marked absorption of water was observed with solutions more hypotonic than rumen fluid, the extent of which was more extensive with less osmotic pressure; the absorption rate as high as 47.6% was obtained with a solution 100 mosmol in osmotic pressure. When hypertonic solution (500 mosmol/L)was infused, however, water was transported on the contrary from the blood to the rumen. Absorption rates of electrolytes such as Na, K and Cl were increased according to the elevation of osmolalities and their concentrations in the test solutions. VFAs were also absorbed in large quantities (23.9-74.5%) in any test solutions, though the absorption rates were significantly decreased with the elevation of osmolalities. These results may indicate that the ruminal wall has a high absorptive function for water, electrolytes and VFAs when the osmolalities and the concentration of solutes in the ruminal fluid are maintained within a certain range. Furthermore, it is thought that they may work as a rational support for a possible oral fluid therapy even in adult cows.
