Guest: Toward Reducing Mineral Excretion From Feeding.

J. S. Radcliffe and B. E. Aldridge are researchers in the Department of Animal Sciences at Purdue University, West Lafayette, Indiana. They say it is clear that most minerals have an active absorption route that is regulated, and this becomes more important as dietary mineral concentrations decrease. A summary of their presentation at the 2008 Alltech Symposium is presented here.

Much emphasis has been placed on reducing nutrient excretion from animal feeding operations over the last decade. Initial reductions in nutrient excretion were relatively easy and were made possible by inclusion of synthetic amino acids, phytase and mineral sources with higher bioavailability.

Mineral excretion results from: 1) indigestibility of a mineral source, 2) lack of absorption of an available mineral, 3) endogenous loss of a mineral that is not reabsorbed and 4) excretion in the urine. Further reductions in nutrient excretion will be more difficult, and will require a better understanding of nutrient absorption and the regulation of nutrient absorption.

In general, it has been assumed that minerals dissociate from their organic or inorganic carrier in the gastrointestinal tract and are then absorbed via a passive and/or active trans- or para-cellular route. Therefore, reported differences in the bioavailability of organic and inorganic minerals have been attributed to differences in disassociation rates of the mineral from the organic or inorganic substrate that they are bound to, or to differences in solubility.

Practically, a better understanding of trace mineral absorption will allow us to better understand how to improve mineral absorption. It is clear that most minerals have an active absorption route that is regulated, and that becomes more important as dietary mineral concentrations decrease.

Therefore, understanding how these transport systems are regulated and determining if other transporters are capable of transporting trace minerals is essential if we want to further reduce mineral excretion. 

Editor’s Note: This commentary is sponsored by Alltech, Inc. The material presented herein is a summary of the author's presentation at the 2008 Alltech Symposium. For more information about Alltech, go to: www.alltech.com

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