Benefits, Safety and Uses of Flax Seed for Horses
By: Dr. Lydia Gray | Updated March 23, 2025 by SmartPak Equine
"Dear Ask the Vet, I have been feeding my horse a product called Reitsport 100 HA. It contains a large amount of flaxseed. I have read that flaxseed has been linked to thyroid problems, cushings disease, lethargy or behavior problems and infertility in horses. Is this true? If it is true, is it a certain type or quality of flaxseed that produces these results. Thank you,"
- LK, Texas
Dear LK,
Every so often I receive a question like yours about the safety of flax seed, so I would like to reassure you and everyone else that feeding flax seed to horses is safe and should not be cause for concern.
To my knowledge, flax seed has not been linked to the problems you list above. On the contrary, research suggests the anti-inflammatory properties of the omega-3 fatty acids contained in flax seed may be helpful in certain medical conditions such as these. For example, omega-3 fatty acids may help prevent laminitis, a major problem in older horses with Cushing’s disease. Also, omega-3 fatty acids may improve the fertility of stallions with certain quality issues.
The next issue is what form of flax seed should be given to horses. You probably know people who grind it, others who soak it, and still others who boil it. The reason people process flax seed in one of these ways is to release the omega-3 fatty acids and other helpful components.
It appears that if whole flax seeds are fed, they simply pass through the digestive tract into the manure and do not provide any benefit to the horse. Therefore the hard outer hull must either be crushed or softened to release the omega-3 fatty acids.
Unfortunately, releasing the helpful components of flax seed also releases harmful components (cyanogenic glycosides and enzymes), which is why some people boil flax seed, to dissipate this precursor to cyanide. However, a recent study confirmed that stomach acid inactivates the enzymes that interact with the cyanogenic glycosides to form cyanide so that is why toxicity is not observed.
By the way, you may hear flax seed or flax seed oil referred to as linseed or linseed oil. Although they are the same thing, if you use linseed oil make sure it is cold-pressed feed-grade and not the solvent-extracted wood finish.
On a final note, if you are grinding flax seed yourself make sure you feed it relatively quickly after grinding and if you are buying pre-ground flax seed make sure it has been stabilized. The omega-3 fatty acids tend to break down fairly easily after processing.
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Video on Feeding Chia or Flaxseed to Your Horse
In this Ask the Vet video, Dr. Gray answers a question on whether its safe to feed horses flax or chia seed, how to prepare them for meal times, and how much to feed your horse.
DAN: "Is there any benefit to feeding horses flax seeds or chia seeds in their grain? If so, how much should you feed?" And I know this is one of your favorite topics.
DR LYDIA GRAY: I'm surprised it's taken this long to sort of float to the top. So the short answer is yes. Next question. So benefits to feeding horses flax seeds or chia seeds. Yes. And the benefits could be just maybe you want to provide more omega 3s period, because they're not on grass. Or they're on a high grain diet, and you're trying to rebalance. Like they're getting too many omega 6s, and you want to bring that balance. Shift it back to a higher 3 to 6.
DAN: So for some people at home who aren't super familiar with omega 3s and omega 6s. What's the difference between the two of them?
DR LYDIA GRAY: Without getting into regulatory jail?
DAN: Yes. I like to put you on the spot like that. Sorry.
DR LYDIA GRAY: You need both.
DAN: OK.
DR LYDIA GRAY: OK. And we don't know for horses what the exact correct ratio is. We think it's about three parts omega 3 to one part omega 6 because that's what grass is.
DAN: OK.
DR LYDIA GRAY: Being the natural food, we're like that makes sense.
DAN: Yeah.
DR LYDIA GRAY: The problem is, in today's modern system of horse keeping when we feed high grain diets that are more skewed 6 to 3, or they don't get fresh grass, their ratio is off. And because 6 tends to form the precursors of inflammatory pathways, we think horses might be in a chronic state of inflammation because their 3 to 6 balance is shifted.
DAN: Got it. So this could help balance it out if they aren't on pasture and are getting grain.
DR LYDIA GRAY: Yep, and take them back out of that chronic state of inflammation.
DAN: Perfect!
DR LYDIA GRAY: Other reasons you might add it is you might want to add calories to the horse, because it's fat. Flax is about 40% fat. Chia not as much. Maybe 30% fat, but still significant. Right? They have significant levels of protein. They have some minerals and vitamins. They both provide mucilage. We'll get into it in a minute. If you soak or cook flax-- have you ever done that? It turns into a gooey, sticky mess in your container, and your spoon will never be the same again. You'll be like, why did I do that? But that's the mucilage in it. And then some people just want to support cellular health and provide omega 3 fatty acids within the cells. It's a wellness idea.
All right. So flax seeds, the biggest question I get asked is how to feed them. I don't think she asked that. She said how much. We'll get to that in a minute. But it's how, so you can feed them just whole. You can feed them ground. You can feed them fresh ground. Like it's feeding time, grind them and feed them. You can buy pre ground and stabilized so they don't go rancid.
DAN: Yes.
DR LYDIA GRAY: OK. And then you can soak them, say overnight, or you can even cook, boil them.
DAN: Wow, this is quite the prep work.
DR LYDIA GRAY: I know. Well you mentioned earlier about a cookbook.
DAN: You're doing a cooking show, for sure. Next episode.
DR LYDIA GRAY: The reason we tend not to feed them whole is because flax seeds have a very hard outer shell or coating. And it's difficult for the horses. If they don't chew them and break it, then their enzymes in their digestive tract can't really open it up either. And then, it just passes out completely unused, and they didn't have access to the nutrients in there. So they didn't get the omega 3s. So that's why we grind them. At my barn, we have a coffee grinder.
DAN: Oh! That's a smart idea.
DR LYDIA GRAY: So we have a container of flax. And then at every feed meal time, we just get out everyone's serving, grind it, pour it in a thing, feed it. So it happens right then. So the omega 3s don't have a chance to interact with the air and sunlight.
DAN: I love that. That's a great idea.
DR LYDIA GRAY: Yeah. And then when they're out in pasture and they hear the coffee grinder, they all come running. So if you want any of our horses, you just put some flax in the coffee grinder and press it. And then they come running.
DAN: Whatever works.
DR LYDIA GRAY: Yeah. But if you don't want to do that, then you can buy some pre-ground stabilized. That's easy. You can soak to soften it, but that's a little bit of a pain. And you don't need to cook or boil them. I like the grinding. I think that releases the nutrients, and it penetrates that hard shell.
And then she wanted to know how much. So it does depend on why you're feeding them and what else your horse is getting and conditions your horse might have. There was a study in the 90s, I think, about horses with sweet itch. And they fed them a pound of flax seed to see if it changed.
DAN: A pound a day?
DR LYDIA GRAY: Yeah. And notice again, we're not talking about volume, like a half a cup, or cup, or a quart, or a scoop, or whatever unit you want to use. We're talking about weight. So the weight that you'll see is you can feed two ounces, four ounces, eight ounces, which is half a pound. 16 ounces, a pound. But it all depends on why you're feeding it. And again I would say, if you were just starting to feed flax seed or chia seed-- which by the way, you don't have to grind or soak or boil.
DAN: Chia, you don't?
DR LYDIA GRAY: No, because it's very small, and there's no hard shell. They get all the nutrients. But if you're adding either of these to your horse's diet, you want to do it gradually. So don't start with eight ounces or 16 ounces. Start with one to two for a week, and then gradually increase it until you get to the amount that you want.
DAN: Everything very slowly with horses.
DR LYDIA GRAY: Yeah. They don't like to be surprised. Trust me.
DAN: I love that. So I know we do also sell other flax products. We have our Smart & Simple Flax, which comes in a powder, which makes it super easy to feed as well.
DR LYDIA GRAY: Pre-ground stabilized, yeah.
DAN: Take a little bit of the work out of it for you as well. There's lots of options on the market, as well.
DR LYDIA GRAY: That one, you mean?
DAN: That was the one! Yes! Convenient that was there.
Research Study: O'Neill, Wendy et al. “Flaxseed (Linum usitatissimum) supplementation associated with reduced skin test lesional area in horses with Culicoides hypersensitivity.” Canadian journal of veterinary research = Revue canadienne de recherche veterinaire vol. 66,4 (2002): 272-7.