Effect of Magnesium and Sulfur upon Cellulose Digestion of Purified Rations by Cattle and Sheep

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Abstract
Fistulated steers and intact lambs were used in an experiment designed to study the effect of magnesium and sulfur upon cellulose digestion and of magnesium upon voluntary feed intake. Purified diets with and without magnesium and sulfur were fed to steers, and rations with and without magnesium were fed to lambs. In vivo cellulose digestion was determined with steers and in vitro digestion measured using inoculum from steers and lambs. Digestion of cellulose was significantly decreased in steers fed the purified rations without added magnesium and sulfur. In vitro digestion was also significantly reduced when rumen fluid from the steers and lambs fed the deficient rations was used as the inoculum for in vitro fermentation. Rumen fluid from lambs fed the complete ration was used for inoculation of a series of in vitro media without magnesium. The serial dilution of magnesium from the original inoculum resulted in a progressive decrease in cellulose digestion. Voluntary intakes of the magnesium-deficient ration were significantly reduced by the third day of consumption. Oral administration of magnesium oxide by capsule to lambs resulted in restoration of appetite, but intravenous injection of magnesium sulfate had a lesser effect.