When Is Horse Feed Too Old To Use?

By Dr Duncan Houston

Old horse feed is one of those barn decisions that feels harmless until it is not. The bag looks mostly fine. It smells “maybe okay.” There is only half a scoop left. And then the very dangerous farm logic appears: “Surely it’s fine.”

Sometimes old feed is just less nutritious. Sometimes it is stale, rancid, mouldy, insect-contaminated, rodent-contaminated, or carrying toxins you cannot see. The problem is that horses are not built to handle spoiled feed well, and the consequences can include feed refusal, colic, diarrhoea, poor performance, weight loss, respiratory irritation, laminitis risk in susceptible horses, and in severe toxin cases, neurological disease or death.

The real question is not only, “How old is this feed?” It is, “How was it stored, what type of feed is it, what does it smell and feel like, and is there any chance it has been contaminated?”

Quick Answer

Horse feed is too old to use if it smells sour, musty, rancid, or unusual, feels damp or clumpy, has visible mould, insects, webbing, rodent droppings, damaged packaging, heat damage, or has been stored in hot, humid, or pest-exposed conditions. Many feed manufacturers recommend using horse feed within about 30 to 60 days of manufacture when stored properly, but storage conditions matter as much as the date. If you are unsure whether feed is safe, do not feed it. The cost of a new bag is much lower than the cost of a colic, toxicity, or neurological emergency. (ker.com)

Do Horse Feeds Have Expiry Dates?

Some horse feeds show a manufacture date, lot number, best-by date, or feed-by recommendation. Others may not show a clear expiry date in a way owners immediately understand. Kentucky Equine Research notes that unlike many human foods, bags of horse feed are not necessarily required to have manufacture or best-by dates, although some manufacturers include them voluntarily. (ker.com)

That means owners should not rely only on the label. A feed can be within a printed date and still be unsafe if it was stored badly. It can also be just past a conservative best-by date and still look physically normal, but its vitamins, fats, aroma, and palatability may already be declining.

The date is useful. The storage history is critical.

Why Old Horse Feed Becomes a Problem

Horse feed does not suddenly turn bad at midnight on a printed date. It deteriorates gradually, and the speed depends on the ingredients and storage conditions.

The main problems are:

• Loss of vitamin potency

• Fat oxidation and rancidity

• Mould growth

• Mycotoxin contamination

• Insect infestation

• Rodent contamination

• Moisture damage

• Heat damage

• Feed refusal

• Digestive upset

In practice, the feed I worry about most is not always the oldest bag. It is the feed that sat in a hot shed, absorbed humidity, was opened weeks ago, had a torn corner, or was stored in a bin that never gets cleaned. That bag has had a whole little ecosystem brewing in it. Not ideal.

How Long Does Horse Feed Usually Last?

There is no single shelf life for every horse feed. A plain pelleted feed, a high-fat performance feed, a textured sweet feed, a supplement, and a vitamin-rich ration balancer can all age differently.

As a general rule:

Kentucky Equine Research states that most manufacturers recommend consuming feed within 30 to 60 days of manufacture when stored properly. Nutrena’s guidance also distinguishes between feed types, noting that pelleted feeds may retain quality longer under ideal conditions while textured feeds tend to lose nutritional quality sooner. (ker.com)

The practical rule: buy what you can use within a sensible window, not what looks like a bargain piled into the feed room for six months.

Bulk buying only saves money if the feed is still safe and useful by the time it reaches the bucket.

Storage Conditions Matter More Than the Calendar

Feed stored in a cool, dry, clean, pest-free room will last much better than feed stored in heat, humidity, direct sun, or rodent-accessible sheds.

Good feed storage should be:

• Cool

• Dry

• Well ventilated

• Out of direct sunlight

• Protected from rain and condensation

• Rodent-proof

• Insect-resistant

• Cleaned regularly

• Organised by first-in, first-out rotation

Recent feed-storage guidance from The Horse emphasises storing grain in secure containers and avoiding open or unsealed bags to reduce vermin contact. Feed storage resources also consistently recommend cool, dry, pest-protected storage to reduce mould, insects, and feed degradation. (The Horse)

A feed bin is not magic either. If you keep tipping fresh feed on top of old crumbs and dusty residue, the bottom of the bin becomes a museum of nutritional regret. Empty and clean the bin between refills where possible.

How To Tell If Horse Feed Is Too Old or Unsafe

Do not feed horse feed if you notice:

• Musty smell

• Sour smell

• Rancid or paint-like smell

• Damp texture

• Clumps

• Caking

• Visible mould

• Colour change

• Excessive dust

• Webbing from insects

• Live insects or larvae

• Rodent droppings

• Chewed bags

• Wet bags

• Heat-damaged bags

• Feed that feels unusually warm

• Feed your horse suddenly refuses

A smell test is useful, but not perfect. Some dangerous toxins may be present without obvious mould. Merck Veterinary Manual notes that fumonisin contamination can be difficult because corn may not look grossly mouldy and may be present inside mixed feed. (Merck Veterinary Manual)

So the rule is: visible spoilage is an automatic discard, but absence of visible spoilage is not a guarantee of safety if the feed source or storage history is questionable.

Mould, Mycotoxins and Why “Just Pick Out the Bad Bits” Is Not Safe

Mouldy feed should not be fed to horses. Picking out visible mouldy clumps does not make the rest of the bag safe. Mould can spread through feed, and mycotoxins may not be evenly distributed or visible.

Michigan State University Extension explains that fungi can produce mycotoxins harmful to animals, and warm, moist conditions are ideal for mould reproduction. Penn State Extension also advises not feeding dusty and mouldy hay or grains. (canr.msu.edu)

The risk depends on the mould, toxin, dose, horse, and duration of exposure. But from an owner’s perspective, the decision is simple: if feed is mouldy, damp, musty, or contaminated, throw it out.

Do not compost it where horses, livestock, dogs, or wildlife can access it. Do not give it to “less valuable” animals. That is not thrift. That is spreading the problem around.

The Corn Warning: Fumonisin and Moldy Corn Poisoning

Corn deserves special attention in horse diets because of fumonisin.

Fumonisins are mycotoxins produced by Fusarium moulds, mainly associated with corn. Horses are particularly sensitive. Merck Veterinary Manual states that horses can develop leukoencephalomalacia after prolonged exposure to as little as 8 to 10 ppm fumonisins in the diet, and once neurological signs begin, death is almost inevitable. (Merck Veterinary Manual)

The FDA guidance for fumonisins is designed to reduce exposure in human food and animal feeds. FDA lists fumonisins as environmental toxins produced by Fusarium species that grow on agricultural commodities in the field or during storage, especially corn, and notes that contamination is influenced by weather, humidity, insect damage, and storage conditions. (U.S. Food and Drug Administration)

A 2025 Delaware Department of Agriculture notice reported equine neurologic cases associated with corn-based feed contaminated with fumonisin, with feed samples exceeding the FDA-recommended maximum level. Reported signs included lethargy, head pressing, wobbly gait, tremors, circling, recumbency, and death. (State of Delaware News)

Practical rule: do not feed untested corn, corn screenings, damaged corn, mouldy corn, or suspicious farm-mixed corn products to horses.

Commercial horse feed from reputable manufacturers is generally safer because ingredients are sourced, screened, formulated, and quality-controlled. Random corn from a local farm, bin cleanout, or “cheap grain mix” can be a very different risk.

Severity and Risk Framework

The most important decision point is this: if the feed looks or smells wrong, it is wrong enough to throw out.

What Can Happen If a Horse Eats Old or Spoiled Feed?

Possible outcomes include:

• Refusing feed

• Reduced performance

• Weight loss

• Poor coat quality

• Loose manure

• Diarrhoea

• Gas colic

• Impaction risk if intake changes

• Laminitis risk in vulnerable horses if feed changes suddenly

• Respiratory irritation from dusty or mouldy particles

• Neurological signs with certain toxins

• Death in severe mycotoxin cases

Not every mouthful of stale feed causes disaster. But you cannot predict which old feed is merely stale and which one is dangerous by confidence alone.

The real concern is not just “old feed.” The real concern is old feed plus heat, moisture, mould, pests, rancid fat, or contaminated corn.

What Else Can Make a Horse Sick After Eating Feed?

If your horse becomes unwell after eating old feed, do not assume the feed is definitely the only cause. It may be, but other problems can look similar.

Important rule-outs include:

Colic From Another Cause

A horse may show colic signs after a feed change, but colic can also come from impaction, gas, sand, parasites, displacement, strangulation, ulcers, or other gastrointestinal disease.

Sudden Diet Change

Even fresh feed can cause problems if the horse is changed onto it too quickly.

Laminitis Trigger

High-starch feed, pasture changes, metabolic disease, PPID, insulin dysregulation, illness, and grain overload can all contribute to laminitis risk.

Infectious Disease

Diarrhoea, fever, depression, and poor appetite may be caused by infection, not just feed spoilage.

Toxic Plants or Contaminated Hay

The problem may be hay, pasture, bedding, or weeds rather than the bagged feed.

Dental Pain

A horse that suddenly refuses hard feed may have dental pain, mouth ulcers, a fractured tooth, or choke risk.

Choke

Feed refusal, coughing, nasal discharge with feed material, drooling, and repeated swallowing may indicate choke, especially if the horse ate dry pellets or beet pulp that was not soaked properly.

If the horse is unwell, treat the horse first and solve the feed mystery second. The bin can wait. The horse cannot.

When Is This an Emergency?

Call your vet immediately if your horse has eaten questionable feed and shows:

• Colic signs

• Repeated pawing

• Rolling

• Looking at the flank

• Not eating

• Depression

• Diarrhoea

• Fever

• Sweating

• High heart rate

• Tremors

• Staggering or ataxia

• Head pressing

• Blindness

• Circling

• Seizures

• Collapse

• Difficulty swallowing

• Choke signs

• Dark urine

• Sudden laminitis signs

• Multiple horses affected after eating the same feed

Neurological signs after possible corn or mould exposure are especially urgent. Fumonisin toxicosis in horses can progress rapidly and has no effective treatment once severe neurological disease develops, according to Merck Veterinary Manual. (Merck Veterinary Manual)

If several horses become unwell after eating the same feed, stop feeding it immediately, keep the bag and lot information, isolate the batch, and contact your vet and feed supplier.

What Should You Do If You Find Old Feed?

1. Check the Date and Lot Number

Look for manufacture date, best-by date, batch code, or lot number. Take a photo before discarding anything, especially if you suspect contamination.

2. Inspect the Bag

Look for tears, water stains, chew marks, insect damage, or signs the bag has been sitting on a damp floor.

3. Smell It

Feed should smell fresh and normal for that product. Sour, musty, rancid, chemical, or unusual smells are enough reason to discard it.

4. Feel It

Feed should not be damp, warm, sticky in an abnormal way, clumped, caked, or dusty beyond normal.

5. Look Closely

Check for mould, webbing, insects, larvae, rodent droppings, foreign material, or colour changes.

6. Compare With a Fresh Bag

If you are unsure, compare the old feed with a new bag of the same product. Differences in smell, colour, texture, or dustiness often become obvious.

7. Do Not Feed Questionable Corn Products

If the feed includes untested corn, corn screenings, bin-cleanout corn, or mouldy corn, do not feed it to horses. FDA guidance and veterinary sources consistently highlight horses as highly sensitive to fumonisin risk in corn-based feeds. (U.S. Food and Drug Administration)

8. Throw Out Anything Suspicious

If in doubt, throw it out. This is one of those phrases that sounds boring because it is correct.

9. Clean the Bin

Do not put fresh feed on top of old residue. Empty the bin, remove crumbs and dust, wash if needed, dry completely, then refill.

10. Monitor the Horse

If the horse has already eaten questionable feed, monitor appetite, manure, attitude, temperature, gut sounds if you know how, and any signs of colic or neurological change.

Common Mistakes Owners Make

Trusting the Date More Than the Feed

A printed date does not protect feed from heat, humidity, rodents, insects, or a wet feed room.

Keeping Too Much Feed on Hand

Buying in bulk can save money only if you use the feed before it deteriorates. Overstocking high-fat or textured feeds is a classic way to waste money and invite rancidity.

Tipping New Feed Onto Old Feed

This keeps old crumbs, dust, insects, and possible mould spores cycling through the bin.

Feeding Around Mould

Do not scrape off mouldy bits and feed the rest. The visible mould is only the part you can see.

Using Non-Horse Feed

Feeds made for cattle, poultry, pigs, or mixed livestock can contain additives or nutrient levels unsuitable for horses. The Delaware Department of Agriculture specifically reminded owners to use feed produced for the species they own after fumonisin-contaminated feed concerns. (State of Delaware News)

Feeding Untested Corn

Corn screenings, damaged corn, mouldy corn, or untested local corn should not be fed to horses.

Forgetting Supplements Expire Too

Vitamins, oils, probiotics, and fat supplements can degrade. A supplement that smells rancid or has changed texture is not a bargain. It is bin food.

How To Store Horse Feed Safely

Good storage prevents most problems.

Use this system:

• Buy only what you can use within a reasonable period

• Store feed in a cool, dry, shaded area

• Keep bags off concrete floors and away from damp walls

• Use sealed, rodent-proof containers

• Keep feed in the original bag inside the bin if possible, so the lot number is retained

• Label bins with purchase date and product name

• Use the oldest feed first

• Clean bins between refills

• Do not mix different feeds in one bin

• Use separate scoops for medicated or special feeds

• Check for pests weekly

• Keep the feed room swept and free of spilled grain

• Avoid storing feed near chemicals, fuel, pesticides, or fertilisers

• Keep lids closed

Humidity is the enemy. Heat is the enemy. Rodents are tiny criminals in fur coats. Feed rooms need to be managed like they matter, because they do.

Prevention: A Better Feed Freshness Plan

A practical prevention plan includes:

• Buying smaller amounts more often

• Recording purchase dates

• Checking manufacture or best-by dates before buying

• Avoiding bags stored outside at retailers

• Avoiding torn, damp, faded, or dusty bags

• Using first-in, first-out rotation

• Keeping feed cool and dry

• Cleaning bins regularly

• Inspecting feed before every use

• Avoiding untested corn

• Using reputable horse-feed manufacturers

• Keeping old feed samples if illness occurs

• Calling the supplier if multiple bags seem abnormal

• Calling your vet if horses become sick

The best feed safety plan is not complicated. It is just consistent. Fresh feed, clean bins, dry storage, no pests, no guesswork.

FAQ

Can I feed horse feed after the best-by date?

Sometimes feed may still look physically normal after a best-by date, but nutrient quality may decline and safety depends heavily on storage. If the feed smells stale, rancid, musty, feels damp, has pests, or was stored poorly, do not feed it.

How long does an opened bag of horse feed last?

Use opened feed as quickly as practical, especially in hot or humid weather. Many manufacturers recommend feed use within about 30 to 60 days of manufacture under proper storage, and opened bags are more exposed to air, moisture, and pests. (ker.com)

Is mouldy horse feed ever safe?

No. Do not feed mouldy horse feed. Do not pick out the mouldy parts and feed the rest. Mould and mycotoxins can be present beyond what you can see.

Why is corn risky for horses?

Corn can be contaminated with fumonisins, which can cause equine leukoencephalomalacia, also called moldy corn poisoning. Horses are very sensitive, and neurological signs can be fatal. (Merck Veterinary Manual)

What should I do if my horse ate old feed?

Remove the feed, save the bag and lot information, monitor your horse closely, and call your vet immediately if there are colic signs, diarrhoea, depression, feed refusal, tremors, staggering, head pressing, blindness, seizures, or multiple horses affected.

Final Thoughts

Horse feed does not have to look dramatic to be a problem. Age matters, but storage matters more. Heat, moisture, insects, rodents, rancid fat, mould, and contaminated corn can all turn a feed-room shortcut into a veterinary problem.

The safest rule is simple: if the feed smells wrong, feels wrong, looks wrong, or has a questionable history, do not feed it. Throwing out a bag of feed is annoying. Treating a colic, toxin exposure, or neurological case is far worse.

Fresh feed, dry storage, clean bins, good rotation, and a healthy suspicion of old corn are not overkill. They are basic horse care.

If your horse has eaten questionable feed, is refusing grain, showing colic signs, or you are unsure whether a feed is safe to use, ASK A VET™ can help you work through the risk and decide when veterinary care is needed.