BLOAT IN FEEDLOT CATTLE: EFFECTS ON RUMEN FUNCTION OF ADDING 4% SODIUM CHLORIDE TO A CONCENTRATE DIET

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Abstract
Four fistulated cows were given alfalfa hay or all-concentrate diets containing either 0.5% or 4.0% NaCl (salt). The low-salt diet leads to the development of rumen conditions associated with bloat. When given the low-salt concentrate diet, cows had rumen fluid with lower pH and protozoal counts, and higher viscosity, soluble carbohydrate concentration, and dry matter content than when they were given alfalfa hay or the high-salt concentrate diet. Massive lysis of bacterial cells was observed in rumen digesta from cows on the low-salt diet and intact cells were full of reserve carbohydrate granules and were surrounded by thickened fibrillar capsules. These changes were largely absent in cows on the other two diets. Water intake and the total water content of the rumen were lower with the low-salt diet than with the other diets. The flow of water through the rumen was highest with alfalfa hay, lowest with the low-salt diet, and intermediate with the high-salt diet. It was concluded that adding 4.0% NaCl to an all-concentrate diet of a type implicated in feedlot bloat increased the flow of material from the rumen and, in so doing, appeared to alter fermentation in such a way as to oppose development of conditions that lead to bloat.