EFFECT OF LEVEL OF FEED INTAKE AND TIME OF SAMPLING AFTER FEEDING ON CONCENTRATIONS OF DISSOLVED SODIUM POTASSIUM CALCIUM MAGNESIUM AND PHOSPHORUS IN BOVINE RUMEN FLUID

Results from feeding trials with four rumen-fistulated cows fed an all-roughage ration at four levels of intake showed significant changes in the concentration of dissolved Na, K, Ca, Mg, and P in the rumen fluid due to level of intake and time of sampling after feeding. Increased intake lowered the proportion of Na and raised that of Ca and Mg. The average K concentrations rose when the intake changed from low to medium levels, but decreased at the high feed intake. Concentrations of P were affected significantly by rate of intake, but changes were irregular and unexplainable. Concentration changes as a function of time after feeding showed significant decreases for Na and increases for K and Mg during the first two to four hours after feeding. Concentrations returned to, or near to, prefeeding levels at the second daily feeding. The hourly concentration changes for Ca and P, even though significant, were irregular, so that no definite trend could be established. In no case was the shape of the mineral concentration curves over the nine-hour sampling period significantly affected by levels of feed intake. © 1969, American Dairy Science Association. All rights reserved.