Vitamin C

Who supplements with vitamin C, how much do you feed and why do you supplement with it?

Horses make their own C so unless the horse is very old, no need to supplement. Is why it’s not in the comprehensive vitamin mineral supplements


This is what I had always thought. But I’ve noticed a few people feeding it to boost immune systems. Would this work?

No. Not for people, not for horses. “Boosts immunity” can be translated to “Does nothing and but we can say this and not get sued.”


“Noticed a few people” doing something in the horse world means nothing unless you have an educated evaluation of who those people are.

Is this the barn fool who already foundered her horse trying to feed free choice hay? Is this your trainer pushing you to add on a pointless supplement? Is this a website selling rose hips for horses? What else do they believe in? Do you have any reason to believe they actually know about nutrition?

The vitamin C and immunity thing was believed for humans in the 1960s and 1970s (Linus Pauling?) but has since been debunked. And humans do need dietary C so they don’t get scurvy. Horses don’t.

Horse nutrition and therapies are where a lot of debunked or failed ideas from human care end up 20 years later.

So I’m not amazed that someone somewhere has the idea of taking outmoded ideas about C in humans and marketing it to horses as a New Thing.

And you are right to come check it out here.

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A lot - way too many - take what they know or think they know about people, and assume it works the same for horses.

People need dietary Vit C, therefore horses do too.
People have a gall bladder to help digest fats, therefore since horses don’t have a GB they can’t digest fat well.

Those are the 2 common ones I see.

Vit C IS needed for a healthy immune system.
Vit C manufacturing can degrade in the older horse.
Vit C may be used faster than it’s made in the hard-working horse (which is not the majority of horses today)

so yes, there are times where supplementing may be necessary full time, or for a short while. And if it’s a shorter while, it needs to be weaned off so the body will recognize the need to ramp up production again.


Was given a tour of a barn and I noticed all the Vitamin C supplement containers in the feed room. There were a lot so naturally peaked my curiosity. I asked the tour giver why people were feeding it and she said to ‘boost immune system’.