Forage is the foundation of every horse's diet, and many UK horses, particularly good doers, receive little else. Grass, hay and haylage supply energy and fibre, but their vitamin and mineral content varies with soil, plant species, season and storage. This guide explains why a forage-based diet may need balancing, how feed balancers differ from vitamin and mineral supplements, which nutrients deserve attention and how to avoid feeding too much.
Why forage-based diets may need balancing
The MSD Veterinary Manual notes that the mineral content of forage depends on forage type, soil and growing conditions, and that the only way to know the mineral content of a forage is to have it tested by a forage-testing laboratory. Two hays that look identical can differ considerably. Vitamins add another layer of variation: vitamin E in particular is unstable and is lost quickly during the storage of hay, while fresh grass is a good source.
World Horse Welfare points out that overweight horses on forage-only diets can be undernourished in protein, vitamins and minerals, and advises feeding a balancer to correct this. The same applies to horses on restricted rations for weight management, horses on mainly stored forage through the winter and any horse fed hard feed at well below the manufacturer's recommended rate, which leaves the vitamin and mineral content of that feed short.
It is also worth keeping deficiency in perspective. The MSD manual observes that reports of uncomplicated nutrient deficiencies in horses are rare, while overconditioning from excess energy is common. The aim of balancing is to cover requirements sensibly, not to load the diet.
Feed balancers vs vitamin and mineral supplements
Both products supply vitamins and minerals, but they are designed differently. Our comparison of a feed balancer vs a vitamin and mineral supplement goes into more detail.
| Feed balancer | Vitamin and mineral supplement | |
|---|---|---|
| Typical form | Pellet fed as a small meal | Powder or small pellet top-dressed on feed |
| Protein | Usually contains quality protein | Usually negligible |
| Energy | Low at the recommended rate | Negligible |
| Feeding rate | Low, set by bodyweight | Very low, often measured in grams |
| Often suits | Good doers, horses on forage only, youngstock and older horses needing protein | Horses that need a carrier-free option or have a tight calorie budget |
Neither is automatically better. A balancer suits a horse that would benefit from extra protein as well as micronutrients. A supplement suits a horse that receives enough protein from forage and only needs the gaps filled. Both work only when fed at the full rate for the horse's bodyweight, a point BETA makes clearly in its guide to labels: feeding less than advised means the product will not be effective, while feeding too much may be wasteful and potentially harmful.
Key nutrients for UK horses
Copper and zinc
Copper and zinc are often discussed together because high intakes of one can interfere with the other. The MSD manual notes that zinc to copper ratios of 3:1 to 4:1 are typical in formulated diets, that excess copper can interfere with selenium and iron metabolism, and that high zinc can impair copper absorption. Forage analysis is the only way to know what your horse is starting from.
Selenium
Selenium has a narrow margin between enough and too much. Deficiency is linked to muscle problems, but the MSD manual notes that toxicity is more likely with oversupplementation, and that horses are more sensitive than cattle. It cites the US National Research Council's suggestion of about 1 mg a day for an average 500 kg horse in light exercise. Selenium in soil and forage varies by location, which is one reason forage analysis and professional advice are useful.
Vitamin E
Horses with good pasture rarely need extra vitamin E, but because it is lost from stored forage, horses living mainly on hay or haylage, or with little grazing in winter, may need a source. The MSD manual links deficiency to muscle disease, among other problems. Your vet can measure blood vitamin E if there is a concern. Seasonal feeding is also covered in our article on winter gut health.
Vitamin A
Vitamin A is rarely a concern for horses with regular grazing. The MSD manual notes that deficiency can develop after more than six months on dried, poor-quality roughage, while excess vitamin A is linked to bone problems and birth defects, so more is not better.
Calcium and phosphorus
The ratio matters as well as the amounts. The MSD manual explains that a calcium to phosphorus ratio below 1:1 can lead to nutritional secondary hyperparathyroidism, sometimes called big head disease. It gives cool-season grasses as typically near 2:1 and legumes such as alfalfa nearer 4:1, while some mature warm-season grasses can fall below 1:1. A forage analysis shows where your horse's diet sits.
Salt
Salt supplies sodium and chloride, and access to salt is a basic part of any ration. Horses that sweat heavily lose these minerals in quantity and may need more, as our guide to electrolytes explains.
Avoiding oversupplementation
Oversupplementation is a real risk, particularly when owners feed several products that each contain a little of everything. The MSD manual lists phosphorus, iron, copper, selenium and vitamin A among the nutrients most often given in excess, and notes that magnesium oversupplementation is more likely than deficiency.
- Add it up. For each product, multiply the additive content per kilogram by the amount fed each day, then total the figures across your balancer, hard feed and supplements.
- Check fortified feeds. Compound feeds fed at the full rate may already meet requirements, so a balancer on top may not be needed.
- Be cautious with selenium. Never add a selenium product without checking what the rest of the diet supplies.
- Do not stack similar products. Two general vitamin and mineral products rarely make sense together.
- Review regularly. Needs change with season, workload and age, so a ration that suited your horse last year may not suit it now.
Life stage matters as well. Growing horses and breeding stock have different requirements, covered in our section on foals and youngstock, while older horses may need help with condition as well as micronutrients.
Getting professional advice
A ration check by a qualified nutritionist is often the most cost-effective step you can take, particularly if you feed several products. World Horse Welfare suggests finding qualified equine nutritionists through feed companies, the Association for Nutrition register or the Equine Nutritionist and Feed Advisor register. Bring your forage analysis if you have one, the labels of everything you feed and an honest note of how much of each your horse receives. Our guide on how to choose a horse supplement explains how to read the additive section of a label.