Since horse health and safety is outside of our area of expertise in home gardening, we recommend that you inquire directly with either Erika Crowl or Amanda Grev, both equine specialist Agents in Extension. Their contact information can be found on the linked pages. The insect pictured does look like a beetle larva, but beetles are an extremely diverse group, and which species it is is hard for us to determine from the photo.

Miri

Thank you!

 

You're welcome!