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The Influence of Potassium, Sodium, Rubidium, Lithium and Cesium on In Vitro Cellulose Digestion by Rumen Microorganisms with Observations upon Sodium and Potassium Influences in Lamb Fattening Rations¹

Iowa Agriculture and Home Economics Experiment Station, Ames

Abstract

A washed suspension of rumen microorganisms was utilized in studying the requirements of rumen microflora for sodium, potassium, rubidium, lithium and cesium in bringing about accelerated cellulose digestion. Interrelationships among these alkali metals were also studied. The presence of potassium in the fermentation medium was found to be essential for in vitro cellulose digestion whereas sodium was without effect in the absence of potassium. A study of interrelationships of varying concentrations of sodium and potassium showed that the addition of sodium to a fermentation medium containing 50 meg. or less of potassium per ml. had either no influence or depressed cellulose digestion. However, when the potassium concentration was from 100 to 400 mcg. per ml. addions of sodium increased cellulose digestion. Chloride was not a limiting factor in these studies.

Rubidium was found to be capable of replacing approximately 50% of the potassium requirement for in vitro cellulose digestion, whereas lithium and cesium were ineffective.

The results of this work indicate that under the fermentation conditions employed a minimum concentration of 100 mcg. of potassium per ml. of fermentation medium is essential for in vitro cellulose digestion. Although sodium is not essential in the strictest sense, it appears desirable to maintain a certain ratio between the concentrations of sodium and potassium for maximum cellulose digestion. Responses in weight gain from sodium and potassium incorporated in a low-ash lamb fattening ration were in harmony with these results.

¹ Journal Paper No. J-3293 of the Iowa Agricultural and Home Economics Experiment Station, Project No. 869.

² Present address: Squaw Butte-Harney Range and Livestock Experiment Station, Burns, Oregon.