In this second article from NRM and McMillan nutritionist Luisa Wood, we take a look at key nutrients that influence the performance horse. The minerals and key vitamins required all play important roles in cardiovascular function, muscle health, flexibility, increased energy storage and utilisation, bone strength and recovery. Therefore, providing correct levels in the diet is essential and often simple dietary changes to meet these requirements can make a significant difference to performance.


Providing the correct level and ratio of amino acids is highly important for muscle development and condition. A performance horse receiving a diet deficient in protein or from poor quality sources will over time begin to show signs of muscle wastage and lack of top line. The most important essential amino acids to provide are lysine, threonine and methionine. Well-formulated feeds will contain protein sources that provide the correct ratio of these daily.

Macro Minerals

Macro minerals are required by the horse in large amounts and will likely be listed on feed bags in grams. 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. The ideal ratio of Ca to P is 2:1. High quality commercial feeds will be balanced for calcium and phosphorous, therefore removing any guesswork required by the owner to ensure the correct ratio is being provided.

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, 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 it plays an important role in neurological functioning and certainly a deficiency can result in an increase of anxious or nervous behaviour, there is very little research linking it to improved behaviour if requirements are met daily, such as through the use of a nutritionally balanced feed.  

Various macro minerals are lost through sweat and supplementing with sodium and chloride through salt, as well as additional potassium through a balanced electrolyte is highly recommended, especially during intense work on warm days. 

Micro Minerals

While micro minerals are required in much smaller amounts such as parts per million, meeting requirements is essential in 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 pastures here that can be 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.


Vitamin E is another strong antioxidant which works closely with selenium. The two nutrients are known to compensate for each other when one is provided in low levels. Vitamins such as vitamin E and the B group vitamins, are found in higher levels in 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. While B vitamins are produced in large quantities during fermentation in the hindgut, 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. 

NRM and McMillan equine feeds have all been formulated to provide the correct amount of all essential nutrients for any performance horse in a balanced way when fed at the correct levels and combined with New Zealand forages. 

For more information or questions on your own horses’ dietary needs, get in touch with your local NRM and McMillan Equine representative.

Article supplied by Luisa Wood, 

Equine Nutritionist