Horses have evolved over millions of years as grazers, with specialized digestive tracts adapted to digest and utilize diets containing high levels of plant fibre. They are capable of processing large quantities of forage to meet their nutrient demands. The small stomach is designed for frequent meals and the large sacculated hindgut comprising the caecum and colon contains billions of protozoa dedicated to fibre digestion. Taken together, this means that a constant intake of forage is essential for maintaining the equine digestive tract and the horse’s overall health.
Inadequate forage intake can increase the risk of various digestive conditions such as gastric ulcers and hindgut acidosis, and it is recommended that each horse consumes at least 1.5% of their body weight in forage every day. Forage through pasture, hay, chaff and fibre products provides a digestible source of energy and varying levels of protein and nutrients. Nutrient levels can vary greatly according to the type of forage, maturity of the plant and where it is grown. For good doers and horses at maintenance, 1.5% of their body weight in forage daily is often adequate for meeting energy requirements and maintaining conditions however due to increased energy requirements, working and breeding horses will require larger amounts and can consume up to 5% of their body weight in forage daily.

Through domestication and limiting grazing areas, the variety of plant species the horse has access to has vastly decreased. Limited grazing combined with the increase in energy and nutrient requirements that comes with work or breeding, has meant that the ability for forage alone to meet energy and nutrient requirements is challenging and unable to be achieved in many cases. This means that once forage requirements are met, often other ingredients are required in the diet to make up for the shortfalls in energy and nutrients, and meet requirements for working and breeding horses. Commercial feeds are ideal in these situations as they are formulated by qualified nutritionists to meet all requirements for various types of horses if a suitable feed is selected and fed at the correct levels.

Feeding the Maintenance Horse

An adult horse that does little or no work and is neither gaining nor losing weight is said to be at maintenance. A maintenance horse has very few physical demands placed on it and therefore has very basic nutrient needs. Most horses at maintenance will require a basic diet of adequate pasture and hay if required, and a low intake balancer pellet formulated to be low in calories but make up for the shortfalls of nutrients in the forage. NRM Equine Balancer is an ideal option here.

If the horse requires more calories to maintain its condition, especially over winter, a high-calorie forage such as Lucerne can be included, as well as a higher intake feed that supplies more calories. Low starch feeds that contain fibre sources such as beet pulp and soy hulls, and high-quality fat sources are ideal for horses at maintenance, as they supply slow-release energy. NRM Low GI Sport or McMillan Grain-Free are great examples of these types of feeds.

Feeding the Working Horse

To achieve optimal performance in any equine sport, meeting the increased nutritional requirements of the equine athlete is vital. While energy is arguably the most important dietary factor and often the first to consider, the various minerals and key vitamins required in higher levels all play important roles in cardiovascular function, muscle health, flexibility, bone strength, increased energy storage and utilisation, and recovery. Therefore providing the correct levels of these in the diet is essential and often simple dietary changes to meet these requirements can make significant differences to overall, health, breeding and performance.

Each mineral and vitamin plays a different role in the horse’s body and contributes to overall health and performance in various ways. Macro minerals such as calcium (Ca) and phosphorus (P) are critical for the constant bone-remodelling process in performance horses, and the amounts and the ratio of Ca:P are both important, with the ideal ratio of Ca to P being 2:1.

Magnesium is another important macro mineral for working horses and has a multitude of roles in the equine body including being one of the major minerals of bone, and working in conjunction with calcium in nerve transmission and muscle contraction. Magnesium is one of the most popular supplemented nutrients in New Zealand mainly for behavioural management.

While magnesium plays an important role in neurological functioning and certainly a deficiency can result in an increase in anxious or nervous behaviour, there are few studies linking it to improving behaviour if requirements are met daily.

Salt and additional electrolytes are one of the most important supplements to provide performance horses as daily sweating will deplete reserves of sodium, chloride and potassium.

Replenishment is essential for maintaining optimum fluid balance in the horse and assisting with rehydration as well as muscle health. While trace minerals are required in much smaller amounts, meeting requirements is essential for the working horse. Studies have shown an increase in the requirement for zinc in exercised horses, and because copper, zinc, and manganese compete for absorption, all three minerals should be increased in feeds for exercising horses.

Selenium is also a popular supplemented nutrient in NZ mainly due to the pastures here that are generally deficient in this important antioxidant. Selenium helps to protect muscles from damaging free radicals and provides immune support. While a deficiency can cause health problems and muscle stiffness and even wastage in working horses, selenium can be toxic at high levels and care should be taken to avoid multiple selenium supplements which could cause over-fortification. Most commercial feeds designed in New Zealand are formulated to meet selenium requirements despite the low levels in NZ pastures.

Vitamin E is another strong antioxidant that works closely with selenium and the two nutrients are known to compensate for each other when one is provided at low levels. Vitamins such as vitamin E and the B group vitamins are found in higher levels in the fresh pasture. Therefore when horses do not have access to pasture and must rely on alternative forage sources such as hay and baleage, a decline in some vitamins in the tissues and blood could result. B vitamins are produced in large quantities during fermentation in the hindgut. However, they are not efficiently absorbed from that section of the digestive tract, particularly when high-grain diets are fed and horses are under the stresses of training and competing.

Examples of high-quality performance feeds in the NRM and McMillan ranges include NRM Ultimate Sport or Sweet Feed, and McMillan Protein Plus, Premium Plus or Muscle Relieve.

Feeding the Broodmare

Nutritional requirements of broodmares change throughout the stages of reproduction, and it is important to adopt a flexible feeding programme to ensure nutrient requirements are being met at each phase. Reproduction can be separated into early pregnancy, which is the first and second trimester or 0 to 7 months gestation, late pregnancy, which is the third trimester or 7 months gestation through to foaling, and lactation which generally lasts for 5 to 6 months post foaling.
In early pregnancy, the mare’s energy and nutritional requirements are similar to maintenance. While it is tempting for owners to increase feed when they discover the mare is pregnant, the ‘eating for two’ rule does not apply unless the mare has a foal at foot and is lactating as well. Increasing feed at this time can often lead to weight gain and associated problems, especially if the mare is generally a ‘good doer’. At this stage of pregnancy, 1.5% body weight in forage and a balancer pellet such as the new NRM Progress is normally sufficient.

Energy requirements in the third trimester are about 15% greater than in early pregnancy, and protein, amino acid and mineral requirements also increase significantly. Foetal nutrient requirements exceed mare’s maintenance requirements at this time and the mare’s diet must be adjusted accordingly. The most important nutrients for the third trimester are the trace minerals zinc, manganese, iron, selenium and copper as these are found at low levels in the mare’s milk. Therefore the foal needs to store these in the liver in the last three months of pregnancy to compensate for the low levels they will be receiving once they are born. Regarding diet, 1.5% body weight in forage and a balancer pellet such as NRM Progress, or a well-fortified feed such as NRM Evolve or McMillan Broodmare is ideal. Additional energy can be supplied in the form of grain or the high fat stabilised rice bran KER Equi-Jewel if needed for weight maintenance.

When the foal is born, the demands of lactation lead to large increases in requirements for energy, protein, calcium and phosphorous. Mares produce milk at a rate of 3% of their body weight daily and weight loss will occur if energy needs are not met. It is important not to underfeed in lactation and always provide adequate calories to prevent weight loss. As well as increasing energy sources in the form of concentrates, lucerne hay provides additional energy than grass hay types as well as a source of protein and calcium. NRM Evolve or McMillans Broodmare are ideal for lactating mares, and additional grain or Equi-Jewel can also be included in the diet to increase calories if required.

Feeding the Growing Horse

Feeding the young growing horse is a balancing act and managing growth to produce a sound athlete while preventing developmental problems, such as skeletal disease is a vital goal in horse production. Energy consumption and the availability of adequate nutrients can influence the growth rates of foals, and meeting nutrient requirements while maintaining optimum body condition throughout the different stages of development is important to optimizing growth. The required nutrients change as the animal grows and the growth rate changes. The transition from foal to weanling can cause problems and some foals may experience a ‘check’ at weaning and maintain or even decrease in weight at this time. The key to minimizing the variability in the animals is to provide an optimal quantity of nutrients for each phase of the growth cycle. This requires that each animal be individually fed a concentrate balanced to be fed with the selected forage.

NRM and McMillan have a range of high-quality breeding feed designed to meet requirements at each stage of growth, including breeding concentrate NRM Progress, which also contains an ingredient called buffered mineral complex (BMC) that has been shown to improve bone density in young horses. NRM Evolve is a complete breeding feed also ideal for providing optimum nutrition for growth and McMillan Rapid Gain is a highly palatable textured feed that is ideal for growing horses requiring additional protein.

High-quality commercial feeds will be balanced for trace minerals and vitamins, therefore removing any guesswork required by the owner to ensure the correct ratio is being provided. NRM and McMillan equine feeds have all been formulated by Kentucky Equine Research to provide the correct amount of all essential nutrients for any type of horse in a balanced way when fed at the correct levels and combined with New Zealand forages.

For assistance with feeding plans to provide a balanced diet that meets all nutrient requirements, consult with an experienced equine nutritionist.