Elk hoof disease is a devastating disease that causes painful lesions on the feet of affected animals and can result in subsequent debilitation and death. It is hard to watch affected elk in the wild. We all want to do something to help.
One idea that many mention to help support elk is placing mineral blocks. We recently conducted a study to begin investigating mineral levels of elk with and without elk hoof disease to find out if this might be a beneficial management action. See the results of the study.
Although normal levels of minerals in elk are not well documented, limited studies suggest levels are lower than expected for some minerals, such as copper and selenium. Mineral supplementation is commonly provided to domestic livestock to support health, including immune function and hoof health.
So could mineral blocks help elk and reduce elk hoof disease? Maybe, but first we need to consider potential risks, benefits, and unintended outcomes. One important risk of mineral blocks, as well as supplemental feeding, is the resulting unnatural congregation of elk. Congregation of animals promotes transmission of infectious diseases. We know from recent experiments that elk hoof disease is an infectious transmissible disease. That means grouping elk around mineral blocks could promote disease transmission through contaminated environments and direct transmission from one elk to another.
Increasing disease transmission through animal congregation is a significant risk. Therefore, the benefit of an action, such as placing mineral blocks, needs to outweigh the risk. To understand the potential benefit, we first need to know if elk are deficient in important minerals.
Mineral levels in organs, such as liver, or in blood are commonly used to assess mineral status of an animal. Unfortunately, in wild animals, these samples are difficult to collect and get to the lab for analysis. However, one sample that was available on feet submitted by hunters and wildlife managers for hoof disease surveillance was hair. Although not the ideal sample, hair has been used in other species (including humans) to evaluate mineral status.
Steven Winter, a PhD student studying elk hoof disease, worked with advisors at Washington State University to analyze mineral levels in hair samples collected from feet of elk with and without elk hoof disease to see if there were differences. Results were recently published in the scientific journal BMC Veterinary Research.
Findings showed that mineral levels in hair varied among elk, making interpretation of differences between the groups more challenging. However, a consistent relationship of lower selenium levels with presence of elk hoof disease was found and indicates that more investigation is warranted.
We did not find that other minerals thought to be potentially protective against hoof disease, such as copper and zinc, were consistently lower in elk with hoof disease. Similarly, there was no indication that increased levels of toxicants, such as arsenic and chromium, contributed to occurrence hoof disease.
We are currently collaborating with wildlife managers in California to investigate the relationship between elk hoof disease and mineral levels in liver, the ideal tissue for analysis, to compare with our findings using hair.
Although we would all like a magic bullet to cure or prevent elk hoof disease, at this point we do not have sufficient evidence to support the benefit of mineral supplementation to elk.
These are, however, important questions, and we appreciate the input to our program. Additional research will continue investigating the role of minerals and potential methods to control disease spread.
Margaret A. Wild, DVM, PhD
Veterinary Microbiology and Pathology
margaret.wild@wsu.edu