Summer Horse Feeding Guide: Balancing Grass, Minerals & Protein

Summer is just around the corner, and as our horses enjoy the freedom of lush pastures basking in the warm sunshine, it is crucial to maintain a thoughtful and effective summer horse feeding regimen.

While we embrace the longer grazing hours, it is important to remember that the nutritional needs of our equine friends still require careful consideration.

What is the best feed for horses when they are in the field? Forageplus discusses a horse supplement approach that starts with the grass your horse will be eating over the summer period.

Listen to this article on the Forageplus Horse Academy Podcast

As a horse owner, the best way to support your horse’s health is by making sure that the minerals in your horse’s diet are enough to support the common mineral deficiencies in spring and summer grass. This can be done by adding a mineral supplement.

Regardless of how well cared for your pasture is, there will always be low levels of certain minerals, which over time can cause horse nutrition deficiencies.

Forageplus are specialists in carrying out scientific forage analysis of all horse forages (grass, hay and haylage) to determine nutritional value.

What this analysis tells us is that spring grass contains great levels of calories (digestible energy) and usually good levels of protein. Vitamin levels are often extremely good, with vitamin E, a vitamin that is found at very low levels in conserved forage (hay and haylage), is very well supplied in the spring and summer grass.

Good digestible energy (DE), good protein and better nutritional quality will often translate into your horse blooming and putting on extra pounds, which is when horse owners knock the bucket feed on the head; but is this the best course of action, or does your field-kept horse still need feeding minerals balanced to the grass it eats?

What Do Spring & Summer Grass Really Provide For Horses?

If you think about it logically, the hay and haylage your horse eats is grass, it is just dried, preserved, stalky grasses. It makes sense that if that dried, preserved grass is not nutritionally imbalanced, then neither will the spring grass be. This is the same grass that will turn into the summer crop of hay or haylage your horse eats in the winter.

In general, forage nutrient content (protein and DE) is highest during the spring when growth is at its fastest from increasing ambient temperatures, lengthening daylight hours and the plant’s programmed wish to flower, set seed and replicate itself.

This means that per mouthful, it is likely that the grass your horse eats, compared to the hay or haylage eaten, will provide more calories, greater levels of sugar and starch and higher protein levels. This results in weight gain. The higher sugar and starch levels coupled with the weight gain are why laminitis is so common during late spring and early summer, compared to the colder months.

Mature summer or dormant winter grass has much lower energy, protein content and overall digestibility when compared to a lush growing, spring pasture. It also tends to have lower and more stable simple sugar levels.

The concentration of some minerals can also be lower with fast spring growth, magnesium can be a good example of this. This is particularly relevant to laminitis-prone horses because magnesium is so important for metabolic health.

The big message is that while spring and summer horse feeding on grass might provide calories in abundance and boost protein levels, it is not more or less balanced from a mineral point of view than any other type of forage so it doesn’t make sense to rely on just calories to maintain optimum health in horses.

People often assume a horse is getting everything it needs if the weight is good. Nothing could be further from the truth, and feeding minerals matched to grass is vital.

Calories are easy to come by in spring from fast-growing pasture. What is hard to come by for a domesticated horse, living in a relatively small area, is a well-balanced, diverse diet high in well-balanced minerals.

When the majority of the diet is short of certain minerals and has excesses of other key minerals, then optimum health, optimum resilience of skin, coat condition, hooves, tendons, ligaments, digestion, metabolism and other vital systems may not be maintained. This can lead to a decrease in physical health and poor performance, especially in the performance horse.

What Summer Grass Often Lacks

While summer grazing can provide horses with excellent levels of calories, fresh fibre, vitamin E and omega-3 fatty acids, it is important to understand that lush grass is not necessarily nutritionally complete.

At Forageplus, our forage analysis data has shown that key mineral deficiencies and imbalances remain remarkably consistent throughout the year, regardless of season.

Although nutrient levels can fluctuate depending on soil type, weather conditions, grass species and pasture management, the same core patterns continue to appear repeatedly across grass, hay and haylage samples.

Protein is another commonly overlooked issue in summer horse feeding. Many owners assume that because horses gain weight easily on grass, protein levels must also be adequate.

However, weight gain alone does not guarantee that the horse is receiving enough quality protein to support muscle maintenance, tissue repair, enzyme production and overall health.

Analysis carried out by Forageplus has shown that around 85% of forage samples tested remain below the minimum protein levels required to sustain optimum health.

While summer grazing can certainly improve protein intake compared to winter forage alone, levels may still remain inadequate for young horses, older horses, broodmares, performance horses and those on calorie-restricted diets.

This is where summer feeding can become misleading. Horses may look well covered externally due to increased calorie intake, while important nutritional deficiencies continue to develop beneath the surface.

Common signs can include poor hoof quality, weak topline, sun-bleached coats, particularly in black and chestnut horses, skin sensitivity, reduced muscle development, exaggerated inflammatory responses and difficulty maintaining overall resilience and performance.

The goal of summer horse feeding should therefore not simply be to provide enough calories, but to create a diet that remains balanced in minerals, protein and essential nutrients throughout the grazing season.

Feeding minerals to horses to balance summer grazing

Whilst most horse owners know that major minerals in the correct ratios are very important to horses, they are less aware of the way that trace minerals contribute to the maintenance of the health and resilience of body systems.

The nutritionally important trace minerals include iron, iodine, copper, zinc, selenium, chromium and manganese. Full-blown, life-threatening deficiencies are rare, but inadequate levels of some of these minerals can produce a variety of symptoms that are very familiar to horse owners.

Two of the most common are poor hoof quality, including a predisposition to thrush, and “bleaching” of the coat. Many black horses will develop an orange tinge, bay horses will become dull and pale, and a rich conker-coloured chestnut may fade to a pastel washed-out shade of orange.

This bleaching of coat colour is due to poor copper reserves affecting the hair shaft and the protection created against UV light.

The resiliency of the immune system may be affected, too.  Common dysfunctions include allergies, exaggerated reactions to vaccines or insect bites, and exaggerated inflammatory reactions in general.  

When copper and zinc are imbalanced with iron and manganese, there can also be an inability to maintain robust tendons, ligaments and other connective tissues.

Zinc and copper deficiencies are extremely common. On the other hand, iron and manganese are rarely low and often very high. They worsen the problem with zinc and copper by competing with them for absorption.

Iodine is highly variable and usually low unless very close to the coast. Conversely, forages from alkaline soils usually have adequate selenium, while all others are borderline to deficient.

Selenium is an interesting mineral.  Supplementation should be done with care, as high levels of selenium are very toxic to horses. 

In years where summer has high temperatures and there is a drought, some forages can become high in selenium.  In general, there is usually an insufficiency of selenium in the majority of horse diets.

How Pasture Management Influences Horse Nutrition

Where horses are constantly grazing on very short pasture, and the soil becomes squashed and compacted by their weight, then horse owners often find it even more difficult to regulate horse weight and maintain hoof and skin health.

The reasons for this are fairly simple. This type of management of pasture leads to high levels of sugar being produced by the plant because it is sick and struggling to be healthy.

A track system or pasture area which never gets rest from horses creates problems, where the health of the soil affects the health of the grass, which affects the health of the horses grazing upon it.

Analysis of grass in these areas will usually reveal high levels of imbalances between both major and trace minerals. Where there is an imbalance in food, then an imbalance of the body is likely to follow.

A better system to reduce forage mineral imbalances is to mimic the migratory grazing which developed our grasslands in the first place, where animals move from one area once the length of the grass reaches around 2 inches onto another area which is around 6 to 8 inches long.  

Grazing in this way creates soil that is not compacted.  It creates grass with more leaf structure, more root structure and lower sugars.  It is also clean. Long grass is clean, short grass is not, and where the grass is dirty, iron levels in the horse’s diet are likely to be high, and this is not desirable.

However, even the best, most carefully managed pasture will still never be rich enough in diversity or large enough in geographical size to provide the diversity of plants to ensure mineral balance.

This means that some form of supplementation will always have to be fed to horses to balance for optimum mineral ratios, even in summer horse feeding. Optimum ratios will allow for optimum absorption and optimum health.

Horses evolved to roam, to select from a variety of plants over huge areas which did not get overgrazed.  The reality is that our domesticated horses are confined to small spaces and fed a relatively narrow diet, and this creates the need to balance to that very carefully, so that optimum health can be supported and maintained.

Managing Weight Gain On Summer Grazing

For many horses, particularly good doers and native breeds, summer grazing can provide far more calories than they actually require. Rapid weight gain during the spring and summer months is extremely common and can increase the risk of metabolic dysfunction, insulin dysregulation and laminitis if grazing is not carefully managed.

Restricting grazing, using track systems, grazing muzzles or feeding lower-calorie forage can all be useful tools for weight control. However, restriction still needs to be balanced carefully to ensure horses continue to receive enough fibre, protein and essential nutrients to support overall health.

At Forageplus, we regularly encounter horses on heavily restricted diets that continue to struggle with weight management despite consuming very little feed. In many cases, successful long-term weight control comes not from feeding less and less, but from creating a better-balanced diet that supports normal metabolic function while carefully controlling calorie intake.

If you would like to understand this topic in more detail, including how to calculate calorie intake from grass and forage, read our article: Horse Weight: 10 Steps To Maximise Control Now.

Do Horses Need Electrolytes In Summer?

Electrolyte supplementation is often heavily marketed during the summer months, but many horses do not necessarily require high-level electrolyte products simply because the weather becomes warmer.

Fresh grass and forage are naturally high in potassium and usually provide substantial calcium.

As a result, the electrolytes most commonly requiring replacement are sodium and chloride, particularly in horses sweating during hot weather, travelling or working harder.

For many horses, providing adequate daily salt alongside a well-balanced mineral intake is often sufficient to support normal hydration and electrolyte balance during the grazing season.

However, horses in harder work, endurance exercise, competition or prolonged sweating may benefit from additional electrolyte support depending on workload, temperature and sweat losses.

To understand this topic in more detail, including the difference between salt and electrolyte supplementation, read our article: Electrolytes For Horses Guide

The Importance Of Grass & Forage Analysis

Every grazing system is different. Soil type, fertiliser use, rainfall, grass species, pasture management and geographical location can all influence the nutritional profile of grass, hay and haylage.

While common patterns appear consistently across the more than 12,500 forage samples analysed by Forageplus, the only way to truly understand what your horse is consuming is through forage analysis.

Testing grass, hay or haylage allows mineral levels, protein content and overall nutritional balance to be assessed accurately. This makes it possible to identify deficiencies, excesses and mineral imbalances within the diet, helping to create a more targeted and appropriate feeding plan.

For many horses, particularly those with laminitis, metabolic issues, poor hoof quality, muscle problems, allergies or ongoing health concerns, forage analysis can provide valuable insight that may otherwise be missed when feeding blindly.

Even where full analysis is not carried out, feeding a well-formulated forage-focused balancer designed around the common deficiencies found in UK forage can still provide valuable nutritional support throughout the summer months.

To learn more about forage analysis and how it can help support your horse’s health, visit our forage analysis page.

Final Thoughts On Summer Horse Feeding

Fresh summer grazing can be an excellent source of calories, fibre, vitamin E and omega-3 fatty acids, particularly when horses have access to good-quality pasture during the main growing season. However, abundant grass does not automatically mean a horse’s diet is nutritionally balanced.

Analysis of more than 12,500 forage samples by Forageplus continues to show that key minerals such as copper, zinc, selenium and iodine frequently remain too low throughout the year, while protein levels are often lower than many horse owners expect.

In UK forage, iron and manganese are commonly excessive and can interfere with the absorption of other essential nutrients.

Successful summer horse feeding is therefore not simply about reducing bucket feed when the grass improves. It is about understanding what grazing genuinely provides, recognising the nutritional gaps that commonly remain, and balancing the diet appropriately to support long-term health.

Whether managing a good doer on restricted grazing, supporting an older horse struggling with topline, or feeding a performance horse through the competition season, the goal should always be the same: providing balanced nutrition that supports metabolic health, hoof quality, muscle function, skin resilience and overall wellbeing throughout the summer months.

Or you can read more of our articles on horse feeding in general.