You most certainly do not need to be a novice, to be confused on the subject of Equine nutrition. There are no longer discussions about whether Vitamins & Minerals are needed for horses, but rather in what amounts they are needed.
All horses have some level of need for each and every vitamin as well as most minerals; it is the exact amount that remains a mystery. Much research has been done in ascertaining the minimum amounts required to prevent deficiencies, whilst very little research on what maximum amounts is required. The ranges for optimum health and performance are luckily large enough to allow for substantial supplementation.
By feeding a formulated grain concentrate, does unfortunately not guarantee your horse is receiving all the required vitamins & minerals in the ‘fully allowed’ amounts, as firstly; feed manufactures are regulated by the department of agriculture, to contain only the minimum amounts of some vitamins and minerals. Secondly; even if the feed did contain the maximum levels allowed, their formula might well be formulated for an intake of 6kg per horse per day, whilst you only feed that particular horse 4kg per day, hence a shortfall of vitamins & minerals.
Pasture kept horses are in all probability also vitamin & mineral deficient, as firstly; due to soil and water deteriation, most hays will be nutrient lacking. Secondly; few hays if any contain all the required vitamins & minerals, for example most hays are calcium rich but contain relatively little Phosphorus. It is imperative that both these minerals are consumed in equal amounts (together) for the growth and maintenance of strong bones and muscles.
To ensure your horse’s optimum health and vitality, a feeding regime of fair concentrates, with a good amount of grass and a complete vitamin & mineral supplement becomes fundamental.
Fortunately most vitamins & minerals have very high toxicity thresholds, so balanced supplementation is a relatively safe practice, without ill effects.
“Large amounts of vitamins & minerals cannot improve a horses performance, but less than optimal amounts will certainly limit their performance, at best”
The above information is compiled from extracts taken from papers presented and accepted by the Council of Nutrient Requirements of Horses – Washington, USA.