[theholisticgoat]

Merck has a video demonstrating what true selenium deficiency looks like in a young kid. It is far different than what we normally see in social media that is actually contracted tendons:
https://www.merckvetmanual.com/multimedia/video/white-muscle-disease-goat

[theholisticgoat]

When asked about selenium max amounts, Doug, FCE’s nutritionist, has this to say in an email:

Your question as to how much is toxic unfortunately is not an easy one to answer. You see many factors affect how much Selenium the animal will need as well as limit it’s uptake.

For example, Iron will bind up Selenium. So let’s say you have a water source that contains high levels of Iron. Animals in this situation will consume more Selenium. Here is another example. If your Animals have parasites they will seek out and consume more Selenium as well.

Amounts that the animal will consume will vary in different situations.

That being said here are some signs that can occur if Selenium is in excess.

Loss of mane and tail from horses

Dullness, lack of vitality, and loss of hair

Sore feet, sloughing of hooves

Stiffness due to joint erosion

Heart atrophy

Sclerosis of the liver