Department of Animal Science to Determine Magnesium Bioavailability from Red Lime

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Animal science undergraduate, Taylor Drane logs data gathered from the study.

Animal science students Brandon Smith, Ashley Young, Elizabeth Backes, Taylor Drane, and professor Ken Coffey have been working in collaboration with James Caldwell from Lincoln University in Jefferson City, Mo., on a study to determine the magnesium bioavailability from red lime. Translation: how much magnesium animals retain from certain feed additives. In this case, the feed additive is red lime. Magnesium bioavailability is determined by measuring the difference in the amount of magnesium an animal consumes and what the animal excretes in its urine and feces. The amount the animal retains in its body shows how available that particular mineral is.

Magnesium is stored in the bones and plays an important role in metabolism. It is necessary to include in animal feed because having too little can cause adverse effects. A lack of magnesium can cause grass tetany in cattle, which can cause convulsions, coma, and death. Preventing just one cow from getting grass tetany more than makes up for the cost of supplemental magnesium.

Magnesium oxide, the standard magnesium supplement for livestock, is highly unpalatable and can cause diarrhea if consumed in excess. Red lime also contains magnesium carbonate which is used as a soil additive to increase amounts of magnesium found in the soil. Magnesium carbonate would have much greater value as a mineral source for livestock, but the bioavailability of the magnesium from the magnesium carbonate is unknown. "This study could give producers and feed manufacturers other options for meeting the magnesium needs of livestock," says Coffey, professor for the department of animal science.

For this study, animals were adapted to their diets for a period of 10 days to allow them to stabilize and for their bodies to reach a steady state for magnesium. Then total feces and urine were collected for seven days. A coarser-ground and a finer-ground magnesium carbonate were used to determine if particle size influenced bioavailability. In the next few months the samples and collected data will be analyzed to determine the potential benefit of using red lime as a source of magnesium in animal feed.