[Bearfootfarm]

It's probably safe but you can buy Selenium supplements made for sheep that allows you more control over the dosage.

https://www.premier1supplies.com/p/...mix+++Vitamin+E+Booster&species_id=0&cat_id=0

https://www.rjmatthews.com/details/Lamb-Kid-Selenium-Vitamin-E-Gel/170-319.html