Food For Thought Horse Series: Soya

Soya For Horses-All You Need To Know

SOYA IN HORSE FEEDS

What Every Horse Owner Should Understand

Soya is one of the most common ingredients used in modern horse feeds. It appears in pellets, mixes, balancers and even supplements. Yet many horse owners do not realise how often it is included in feeds, or how many different names it can appear under on an ingredient list.

You may see the words soy or soya, but you may also see less obvious names that still refer to the same ingredient.

Understanding what you are actually feeding your horse starts with recognising these different terms.

SOY OR SOYA – WHAT IS THE DIFFERENCE?

The terms soy and soya refer to the same plant.

The difference is simply regional language.

Soy is more commonly used in American English, while soya is the term more often used in the United Kingdom, Europe, Australia and New Zealand.

Both words refer to soybeans, a legume seed that is naturally high in protein and oil. These beans are processed into several different ingredients used in animal feeds.

So whether a label says soy meal or soya meal, it is referring to the same source.

WHAT SOYA IS USED FOR IN HORSE FEEDS

Soya is often included in horse feeds as a concentrated protein and energy source.

It can appear in several processed forms including:

Soya meal

Soy meal

Full-fat soya

Roasted soybeans

Soybean oil

Soya oil

Soy protein

These ingredients are used by feed manufacturers to increase protein content and improve feed formulation.

While this may sound beneficial, the important question is whether the individual horse actually needs additional protein in the first place.

For many horses, the answer is no.

THE HORSE WAS DESIGNED FOR FIBRE

Horses are hindgut fermenters. Their digestive system evolved to process fibre from grasses and forage almost continuously.

Inside the caecum and colon, billions of microbes break down plant fibre and produce energy for the horse. This microbial ecosystem works best when the diet is simple and forage-based.

Grass and hay form the natural foundation of the horse’s diet.

When concentrated ingredients are added unnecessarily, the digestive balance can begin to shift.

THE PROTEIN PROBLEM

One of the most common issues with soya-based feeds is excess protein.

Many horses already receive adequate protein from pasture and hay. When additional protein is added through feed concentrates, the horse must metabolise the excess.

The body removes this extra nitrogen through urine, which places additional workload on the liver and kidneys.

Owners often notice a strong ammonia smell in urine or stables when protein intake is higher than the horse actually requires.

In many cases, the extra protein is simply being wasted.

HIDDEN NAMES THAT MAY INCLUDE SOYA

One of the challenges for horse owners is that feed labels do not always clearly state soy or soya.

Instead, more general terms may be used.

Examples can include:

Vegetable protein meal

Vegetable protein concentrate

Vegetable protein

Plant protein

Vegetable oil

Plant oil

Legume protein

These ingredients can sometimes include soybean derivatives, depending on the formulation of the feed.

This does not mean every ingredient under these names contains soy, but it does mean the presence of soy-based ingredients may not always be obvious.

For horse owners trying to simplify diets or avoid certain ingredients, it is important to look carefully at feed labels and ingredient lists.

THE HINDGUT MICROBIOME MATTERS

The hindgut microbiome relies heavily on fibre fermentation.

When horses are fed diets containing increasing amounts of processed concentrates, protein meals or grain-based feeds, microbial balance can begin to change.

In some horses, this may contribute to:

Loose manure

Faecal water

Gas production

Digestive discomfort

Behavioural changes linked to gut stress

These signs are often described as a horse being sensitive, when in many cases, the diet may simply be too complex for the digestive system.

WHEN SOYA MAY HAVE A ROLE

There are situations where additional protein can be beneficial.

Growing horses may require higher protein levels to support development.

Lactating mares need additional nutritional support.

Some performance horses or horses rebuilding muscle may benefit from targeted protein supplementation.

The key point is that these feeding decisions should be made because the horse needs the support, not simply because the ingredient is common in commercial feeds.

KEEPING HORSE DIETS SIMPLE

For most horses, the healthiest feeding approach remains simple and forage-based.

Grass (not faming grasses)

Low sugar hay

A stable hindgut microbiome

Support can then be added only when there is a clear reason to do so.

Many horses improve dramatically when diets are simplified and unnecessary ingredients are removed.

A SIMPLE RULE TO REMEMBER

Horse feeding has become increasingly complicated.

Yet the healthiest horses are often those fed the simplest diets.

Before adding another feed, supplement or ingredient, it is worth asking one simple question.

Do not feed it unless you need it.

Consultation Support

If you would like help assessing your horse’s diet, Natural Horse offers personalised Horse Support Consultations. These consultations help identify dietary triggers, simplify feeding programs, and support hindgut health for the individual horse.

Book a consultation here:https://www.naturalhorse.co.nz/horsesupportconsultations

Disclaimer

The information provided in this article is for educational purposes only and is intended to support horse owners in making informed feeding decisions. It is not intended to replace veterinary diagnosis or treatment.

Every horse is an individual and nutritional needs vary depending on age, health status, workload and environment. Owners should consult with a qualified veterinarian or appropriate professional before making significant changes to a horse’s diet.