What is Vitamin E and When Does a Horse Need It?
Normally horses will provide themselves with all the vitamins they need if they have a good basic diet (even if its pasture only) and access to daylight etc and they can create vitamins within themselves and also store vitamins. However, Vitamin E (alpha tocopherol) is an essential vitamin – meaning that the horse has to ingest it daily and its source is green feed – i.e. good quality pasture. Therefore it is possible that levels can become low at times and so unlike other vitamins, at these times horses will need supplementation of this vitamin. The need to supplement Vitamin E will occur firstly when the green feed intake is reduced – typically when on winter pasture, or wet trampled pastures, or drought conditions. Also a need to supplement applies when horses may be deliberately restricted from pasture in the spring in order to keep the hype of spring grass affecting the behaviour. A shortfall can also occur when a horse is a poor or restless grazer, and particularly when a horses is stabled and is not being given fresh green fodder such as fresh lucerne chaff (which is a good source of this vitamin). It is important to note that storage of green fodder will also reduce the availability of Vitamin E.
Why Does a Horse Need Vitamin E?
Vitamin E is needed for the correct functioning of the nervous system so low levels of Vitamin E in the diet can result in horses being nervy. It also can affect muscular efficiency and performance and has been attributed to creating susceptibility to tye up syndrome. It is often recommended in conjunction with selenium for horses prone to tying up. The other very specific need is for breeding stock – both mares in foal and lactating, weanlings and stallions. The demand for Vitamin E is higher in breeding stock, necessary for proper function of the reproductive systems, and therefore these animals should always be provided with daily Vitamin E.
The greater the performance demands on a horse – the greater the need for vitamin E. This is because of its contribution as an efficient anti-oxidant and therefore supplementation is appropriate to offset the development of free radicals (the result of cellular energy transfer) which is of course increased in horses working harder. It is vital to offset these, as they can cause oxidative stress and hence damage to cells and cell membranes, by providing a good anti-oxidant supplement. This will maintain the integrity of the muscle structure, and prevent muscle damage.
So as well as being necessary for the proper function of the reproductive, muscular, nervous, circulatory and immune systems, it’s most important function is as an antioxidant protecting damage to the cells which can result in permanent tissue, muscle damage and vulnerability to disease and reproductive problems.
Which Vitamin E
Two types of vitamin E are available – synthetic and natural. The horse sources natural Vitamin E from pasture and green feed. The supplemented Vitamin E has two sources, one is a natural tocepherol and the other a synthetic one.
It has been shown that a natural Vitamin E supplement is better as it has a higher biological activity and acts more quickly. The negative though, is the very high cost. In animals other than horses the size of the dose can be substantially reduced with natural Vitamin E therefore offsetting the cost, however, in horses this does not apply and the slight dose reduction still leaves the cost very high. It is more economic to give a higher synthetic Vitamin E dose. Synthetic Vitamin E will still provide the daily requirement and optimum levels in the plasma achieved at a lower overall cost.
At the end of the day synthetic Vitamin E has been scientifically shown to lift the levels in the physiology of the horse to prevent the effects of low consumption from green feed, high work demand and breeding levels.
The Special Need for Vitamin E in Breeding Horses
With regard to breeding animals, scientific study (Hoffman et Al 1999) showed that Vitamin E is easily transferable and mares that were supplemented with Vitamin E showed increased passive transfer of antibodies to foals, which greatly enhances the immune system. It also showed an advantage of feeding Vitamin E during late gestation and early lactation; and that serum and colostrum IgG levels were greater in mares supplemented with Vitamin E. The foals from all mares had similar levels of IgG, IgA, and IgM at birth prior to nursing. After nursing, foals from mares fed the high level of Vitamin E were found to have higher serum levels of IgG and IgA, which were reflected in the dam’s colostrum. It has also been suggested (Harper, 2002) that mares known to have poor-quality colostrum, or that had foals with failure of passive immunity transfer in previous years, should be supplemented with twice the Vitamin E normally fed for at least a month before and after foaling. It was also recommended that pregnant mares fed lower quality hay should be given Vitamin E supplementation a month before and after foaling.
Vitamin E has been linked with increased libido and semen quality in stallions. In addition to these characteristics, one of the most important functions of Vitamin E in stallions is cell membrane protection. The lipids in cell membranes are vulnerable to attack from harmful compounds known as free radicals or reactive oxygen species (ROS) that are produced in the mitochondria of cells. The body’s defence mechanisms against free radicals and ROS are enzymes and nutrients referred to as antioxidants. Vitamin E, a natural antioxidant, reacts with free radicals and ROS to protect cell membranes. Research has suggested that fatty acids in sperm cell membranes are crucial to fertilizing capacity, so the nutrients that protect the fatty acids are just as important. Sperm motility is commonly used as an indicator of oxidative stress. Practices such as chilling, freezing, and shipping semen increase oxidative stress.
How Much Vitamin E is Needed by a Horse
A 500kg horse on pasture and resting needs 375 iu per day, a lactating mare or a working horse needs 1200 iu daily. However when green feed is rest