Supplement Overload? Here’s What Your Horse Really Needs

The “must-consider” horse supplements (and when they actually matter)

Walk into any stockfeed store these days and… yep — it’s supplement overload. Powders, pellets, oils, pastes, tubs, scoops with big promises on the label. It can feel like you need everything just to be doing right by your horse.

Here’s the good news: most horses don’t need a cupboard full of extras. But there are a few nutrients that commonly come up because they’re either:

• naturally low in typical hay-based diets, or

• easily lost during harvest/storage, or

• hard to consistently hit at the right intake without planning.

Let’s break down the big ones we see most often — and what to do about them.

1) Vitamin E: the classic “hay-fed horse” gap

Vitamin E is a powerhouse antioxidant that supports immune function, muscle and nerve health, and recovery. Horses can’t make it themselves — they rely on what’s in their diet.

Fresh green pasture is usually a great source. The problem? Vitamin E drops quickly once grass is cut and cured into hay. Research summaries and industry references commonly report large losses during harvest and storage — often in the “significant to massive” range depending on conditions. 

So who should consider a Vitamin E supplement?

• Horses on mostly hay (especially long-term)

• Horses with limited/no pasture access

• Horses in harder work, poor doers, older horses, or those needing extra muscle support (discuss specifics with your vet)

How much do they need?
General minimum guidance is often quoted around 1 IU/kg bodyweight/day (so ~500 IU/day for a 500 kg horse), with higher “working horse” guidance commonly around 800–900 IU/day for light to moderate work. 

Options you’ll see in-store:
Vitamin E products like KER Nano-E, Virbac White-E, Ranvet Muscle E, and Kohnke’s Own Mag-E are popular choices when pasture isn’t doing the job.

Quick note: Vitamin E and selenium are often talked about together — but selenium is one you don’t want to “guess” with, because oversupplementation can be risky. 

2) Lysine: the amino acid that helps “protein actually work”

If you’ve ever fed “enough protein” but still struggled to build topline, this is the conversation.

Lysine is an essential amino acid (horses can’t make it) and it’s often the “limiting” piece that determines how well your horse can use the protein in the diet for muscle, tissue repair, growth, and general condition. 

It tends to be most relevant when diets are:

• mostly grass hay + cereal grains

• low in quality protein sources (or inconsistent forage)

How much lysine?
Modern references commonly cite around ~27 g/day for a 500 kg adult horse at maintenance, with requirements changing significantly for growth, lactation, and higher demands. 

In-store options:
Straight lysine products (like L-Lysine powders) can help tidy up a ration when the rest of the diet is solid — especially if you’re targeting muscle development. 

3) Omega-3s: for coat, skin, inflammation support (and “pasture vs hay” matters)

Omega-3 fatty acids support healthy inflammatory responses and cell membranes, and many owners notice benefits in coat, skin comfort, and general “thriving” — particularly when horses aren’t on fresh grass. 

Fresh pasture contains more omega-3s than hay-based diets, which is why the “hay-only horse” often ends up a bit short. 

Common omega-3 sources:

• Linseed/flaxseed (whole, milled/ground, or oil)

• Stabilised omega oils designed for horses such as KER EO-3

(If you’re using oils, remember: adding fat can change the overall ration — and some horses need gradual introduction.)

4) Salt & electrolytes: the one most horses still don’t get enough of

Here’s a big one. Forage and many feeds are naturally low in sodium, so horses often need salt added intentionally. 

A commonly cited baseline for a 500 kg horse at rest is around 10 g sodium and 40 g chloride per day, and needs climb with heat and sweating. 

But what about a salt block?
Salt blocks can help, but many horses don’t lick enough to meet daily needs reliably. Loose/top-dressed salt is often more consistent. 

And iodine?
Iodised salt can be useful — but iodine is one of those nutrients where too much can cause problems, especially if it’s already coming from a fortified feed or kelp-based products. 

The real “secret”: balance first, supplement second

Supplements work best when the foundation is right:

1. forage quality + quantity

2. an appropriate base feed (if needed)

3. then targeted extras to fill true gaps

If you want to be really confident, consider a forage/feed analysis or chat with your vet/equine nutritionist — it can save money long-term and helps avoid the “expensive manure” problem (or worse, accidental overdoing of certain nutrients). 

Pop in-store or shop online, and if you’re unsure, message us — we’re always happy to help you choose the right option for your horse.