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Magnesium and Calcium Utilization in Sheep Treated with Magnesium Alloy Rumen Bullets or Fed Magnesium Sulfate

U.S. Department of Agriculture, Ithaca 14853

Abstract

A metabolism trial was conducted to assess some effects of magnesium alloy rumen bullets and magnesium sulfate on magnesium and calcium utilization in wether lambs fed a basal, semipurified diet (800 g/day) that contained .08% magnesium and .42% calcium. Four sheep were assigned randomly to each of four treatments: basal diet only (BD); basal diet plus two commercial magnesium bullets per animal (AB); basal diet plus two experimental magnesium bullets per animal (EB); basal diet plus supplementary magnesium (1 g/day) as magnesium sulfate (MgSO₄). The bullets were administered at the beginning of a 9-day collection period. Both forms of magnesium supplementation increased (P<.05) plasma level, fecal excretion and urinary excretion of magnesium. Mean plasma magnesium levels (mg/100 ml) for the respective BD, AB, EB and MgSO₄ treatments were 1.9, 1.9, 1.7 and 1.9 initially, and 1.9, 2.6, 2.7 and 2.3 after 9 days of treatment. Fecal excretion of magnesium was greater (P<.05) and urinary excretion was lower (P<.05) in sheep given magnesium bullets than in sheep fed magnesium sulfate; differences between treatments AB and EB were not significant. Urinary calcium excretion tended to increase with magnesium supplementation, but the treatments had no effect (P>.05) on plasma level, fecal excretion, or apparent retention of calcium. These results indicate that magnesium rumen bullets can provide substantial amounts of magnesium to sheep. However, as indicated by weights of bullets recovered from four sheep fed the semipurified diet, or from six sheep fed grass hay in another trial, the rate of decomposition of the bullets in the reticulo-rumen was highly variable.

¹ U.S. Plant, Soil and Nutrition Laboratory, Agricultural Research Service, Ithaca, NY 14853.

² Snake River Conservation Research Center, Agricultural Research Service, Kimberly, ID 83341.

³ The authors gratefully acknowledge the advice and assistance of Dr. D. E. Hogue and Mr. C. L. Heffron, Department of Animal Science, Cornell University, in conducting the feeding trials. The cooperation of Pfizer International, Inc., NY, is also acknowledged.