Naturally occurring selenosis in Wyoming.

This research article surveys the instances of selenosis, a toxicity condition due to excess selenium, in animals of Wyoming, from 1947 to 1991. Despite previous reports of widespread selenium-related animal deaths, the review discovered only four confirmed cases of natural selenosis during this period, all in horses.

Research Context and Methodology

• The study investigates the occurrence of selenosis in animals across Wyoming, focusing on a time frame between 1947 and 1987. The researchers relied on records from the Wyoming State Veterinary Laboratory for their initial investigation.
• Contrarily to older assertions which alleged thousands of annual animal deaths due to selenium, the researchers found no cases of naturally occurring selenosis.
• To further explore the issue and provide more recent data, beginning in August 1988, the researchers reached out to veterinarians and livestock producers via announcements in various statewide livestock publications, requesting them to send suspected cases of selenosis and selenium deficiency.

Results and Findings

• Despite the widespread solicitation, only four cases of naturally occurring selenosis were confirmed from August 1988 to August 1991. Notably, all the cases were horses.
• The clinical signs observed in these horses mainly pointed to epithelial damage, including hoof lesions and loss of mane and tail. None of the cases showed any neurological signs, which are sometimes associated with selenosis.
• The identified sources of selenium in these cases included the native range and grass hay. Therefore, the natural local environment and diet appeared to be the primary factors leading to these rare instances of selenium over-exposure in horses.

Conclusion

• The research provided evidence contradicting large-scale historical reports of selenium-related animal deaths in Wyoming.
• Instead of previous estimates, only a small number of selenosis instances were confirmed in a targeted study over multiple decades, suggesting that naturally occurring selenium toxicity may not be as prevalent in Wyoming as previously thought.
• Further research is needed to better understand how environmental factors and food sources impact the selenium levels in livestock and how to manage potential selenium toxicity to enhance animal health.