SODIUM AND POTASSIUM CONCENTRATIONS IN RUMINAL CONTENTS AFTER FEEDING BLOAT-INDUCING ALFALFA TO CATTLE

Abstract

Postprandial fluctuation of ruminal cations was determined in cattle with different susceptibilities to alfalfa bloat. Rumen contents were sampled before feeding and at regular intervals after feeding fresh alfalfa to determine the changes in concentration of sodium (Na) and potassium (K). Levels of Na and K changed dramatically 1.5–2.5 h after feeding. When compared to prefeeding levels, Na concentrations were lower but K concentrations were higher immediately after feeding fresh alfalfa. When rates of change of the ion concentrations were examined during the 8-h postprandial period, differences among animals were not detected (P > 0.05). Sodium levels in ruminal contents consistently increased after feeding and K levels decreased to prefeeding levels. However, bloat-prone animals had lower average Na but higher K concentrations than the less susceptible animals. The resultant shift in the ionic equilibria may contribute to the occurrence of bloat through colloidal aggregation of chloroplast particles. Key words: Legume, bloat, alfalfa, cattle, rumen cation concentrations