Research has shown that horses on a hay-only diet may not digest some nutrients as effectively as those fed forage alongside a fortified feed making it all the more important to provide supplementation.



With winter just round the corner and grass growth stunted by the UK’s arid summer many horse owners are feeding hay or haylage earlier than usual. But simply feeding horses hay only may not be enough for optimum health, even if it meets their energy needs and satisfies their psychological need to chew.


A study published last year by WALTHAM®, who provides the science underpinning the SPILLERS brand, in collaboration with Michigan State University, discovered that feeding a hay-only diet resulted in reduced digestibility of many micro and macro minerals (such as calcium, magnesium, copper and zinc).


Hay for horses


The study involved a group of healthy adult horses and a group of healthy aged horses being randomly assigned on a rotational basis to one of three diets that supplied similar gross energy over a five week period: hay, hay plus a starch and a sugar rich fortified feed or hay plus an oil and fibre rich fortified feed. The micro and macro nutrient digestibility was determined for each diet.


An analysis of faecal and urine samples showed that the horse’s ability to digest key nutrients does not appear to decrease with age across any of the three diets fed. However, perhaps most importantly the digestibility of various macro and micro minerals (including key trace elements) was consistently lower when fed the hay diet compared with the other two diets.



This indicates that micro and macro minerals are less available to the horse when feeding a hay only diet than when the hay is fed together with a fortified feed. This strongly suggests that horses and ponies fed hay only diets may require additional supplementation such as a balancer to maintain good health and well-being.


Comparison of nutrient digestibility between three diets for aged and adult horses (2017) Sarah Elzinga, Brian D. Nielsen, Harold C. Schott, Julie Rapson, Cara I. Robison, Jill McCutcheon, Ray Geor and Patricia A. Harris. Journal of Equine Veterinary Science, vol 52 p89