Why are Balanced Equine mineral mixes NOT the ‘everything but the kitchen sink’ type?
Many companies put a broad range of minerals and vitamins in a product to appeal to those horse owners who are not aware that many of the minerals and vitamins either come from pasture or hay and other feeds (grass and hay can be a rich source) or that microbes in the gut manufacture many nutrients. Many nutrients call these products ‘kitchen sink’ type. Something has to be useful, the rest are generally excreted.
Following are *some* examples – this is not a complete list:
It is known that forage contributes on average, 10-50 ppm boron, depending on soil types and conditions (NRC 2007 Nutrient Requirements of Horses). The NRC states that “it is assumed that the natural background levels in forage are sufficient to meet the very small requirements for these trace elements in horses”. They further state that “the supplementation of these elements, including the rare earth elements, is not based on scientifically elaborated, valid data, and has the potential to be dangerous to horses.“
Recently, cobalt has been in the headlines as cobalt (cobalt chloride) is considered a banned performance-enhancing supplement in the racing industry. Dr Kellon VMD says “Grass (and hay) and other plants contain cobalt and is considered adequate for horses. Cobalt has no known function inside the horse except as a component of vitamin B12. B-12 is essential for fatty acid metabolism, DNA synthesis and the conversion of folic acid into an active form. Vitamin B-12 is not present in the equine diet, instead it is produced by intestinal microorganisms and absorption was studied in the 1970s. No vitamin B-12 deficiency has ever been documented and oral or injectable B-12 leads to only transient elevations in the blood levels followed by rapid excretion.”
The NRC Nutrient Requirements of Horses, page 88 says “Filmer (1993) reported that horses remained in good health while grazing pastures that were inadequate in cobalt for ruminants.” “Considering that the occurance of deficiency symptoms in cattle and sheep were observed at concentrations of less than 0.04 to 0.07 mg/kg dietary DM, and considering that horses are tolerant of lower concentrations than cattle, the recommended minimum amount has been set at 0.05 mg/kg dietary DM. This should be typically met through the consumption of normal feedstuffs.”
See links below for NRC book.
We do know that too much cobalt is toxic. There are a number of studies looking at this, symptoms have been found to range from colic like symptoms, excessive sweating, anxiety, trembling to collapse. Daniel Ross has an informative article on cobalt, see link at bottom of page.
Chromium has been found to be beneficial in rats and people by decreasing insulin levels and improving glucose disposal in type 2 diabetic and obese humans. There are studies that show chromium supplementation has been beneficial in healthy horses by enhancing glucose regulation. In insulin resistant horses, the results have been mixed. Some show some benefit but other studies have shown no effect on insulin regulation, most likely due to there being no chromium deficiency. The problem with supplementing chromium is that if there is no deficiency, more can lead to chromium toxicity. Chromium is taken up very easily by plants in neutral and acidic soils and is unlikely to be deficient unless the grass or hay is grown in alkaline soils. There are many studies on chromium toxicity in plants where it is considered an environmental pollutant and plant toxin. Any recommendation for chromium supplementation in horses should be considered carefully in the light of whether there is a deficiency to start with.
Dr Eleanor Kellon VMD advises “Chromium shows up in just about every commercial supplement for IR horses. It’s true that chromium is important for insulin signalling but unless your horse’s hay was grown on very alkaline soils there’s little, if any, chance that the diet is chromium deficient. Chromium is taken up very easily by plants in neutral and acidic soils. Soil levels are generous to begin with and magnified by the use of biosolids, manure or industrial by products such as fertilisers. In the US, soil levels of chromium in many areas are high enough to attract the attention of the Environmental Protection Agency. Chromium, like anything else, is toxic in excess.”
It’s interesting how feed/supplement companies have made horse owners think that they need to supplement vitamins. Research has shown that it’s unnecessary to supplement vitamins for horses on high forage diets. Of course, there may be exceptions but they are literally exceptions to the rule. Many of the vitamins are manufactured by the horse (via gut microbes) or are in the pasture and hay that horses eat. The only exception is vitamin E for horses that are fed significant quantities of processed feed/hay or are on a workload. See below about vitamin E.
Vitamin A (trans-retinol, present in the diet in the form of carotenoids) is an interesting inclusion in many vitamin and mineral products as supplementation is only required if the intake is based on bleached (not green) hay or hay that is more than 12 months old. Grass and green hays like lucerne and grains are rich sources of vitamin A. Carrots contain roughly 8500 IU vitamin A (as beta-carotene) in a 17.5 to 20cm carrot. Too much can be toxic. When toxic, vitamin A can cause bone fragility, developmental bone disease in young horses, abnormal bone deposits and sloughing of the skin.
Biotin, (a water soluble B vitamin) assists chemical reactions in the body including synthesis of protein for keratin formation. Biotin and the rest of the B vitamins are manufactured by gut microorganisms and can come from the diet in the form of fresh grass. There are a number of studies that show that biotin can improve hoof quality but other studies found no change at all with biotin supplementation. Biotin only helps if there is a deficiency to start with. For horses that are mainly on pasture, it’s less likely for a deficiency to exist and even more so if the horse is also fed biotin sources like grains, brans and seed meals. However if the diet contains a lot of grain, biotin is more likely to be deficient as high grain diets in cattle have been shown to increase the acidity in the rumen, decreasing the activity of bacteria that synthesise biotin. This may well occur in horses. Some examples of studies are at the bottom of the page.
Vitamin D is produced in the skin, no dietary intake is required if the horse has some exposure to the sun. Vitamin D is also abundant in hay, especially if less than 1 year old. Too much vitamin D can cause calcification of the aorta and other soft tissues, sometimes hypercalcemia and death. Upper safe limit of intake is 44 IU/kg of bodyweight. Dr Eleanor Kellon VMD NRCPlus
Vitamin “K is present in the diet in the form of phylloquinone (in plants) and is also synthesised by the bacteria colonising the gut in the form of menaquinone. K is needed for activation of blood proteins involved in clotting, bone metabolism (the hormone calcitonin and calcium binding to bone scaffolding) and may inhibit calcification of blood vessel walls. Critical functions to be sure but no diet related deficiency of vitamin K has ever been documented or suspected in horses. While the current NRC mentions the possibility that intestinal absorption of bacterial source menaquinone might not be adequate to meet needs, work in other species that they didn’t cite clearly shows large bowel absorption. Despite this, menadione (synthetic) is commonly added to feeds and supplements for high performance horses with lung bleeding (EIPH – exercise induced pulmonary haemorrhage). While relatively non-toxic, it’s also useless.” Dr Eleanor Kellon VMD NRCPlus
We need more research about the various forms of vitamin K.
What about Vitamin E?
Vitamin E is an important antioxidant, especially in the nervous and immune systems but it should NEVER be stored with other minerals as it is acts as a preservative. For this reason vitamin E is NOT in any of the mineral mixes. Vitamin E is abundant in grass so doesn’t need to be supplemented for horses in no work on high fresh forage intakes but many studies have shown horses benefit from vitamin E supplementation when on higher workloads.
Vitamin E added to feeds or multi ingredient supplements is oxidised very quickly so should be added separately.
The best value source is human liquid vitamin E capsules. Technically you could use either synthetic or natural as 400 natural IU should be equivalent to 400 synthetic IU, though there is some evidence that natural vitamin E could be twice as bioavailable as synthetic vitamin E. However, this may be due to the lack of fat mixed directly with the Vitamin E, rather than synthetic vs natural. IU = International units, the number of IU is a measure of potency.
Throw the capsules straight into a feed bucket, many horses happily eat the capsules but if a horse is a bit picky, the next best option is to soak the capsules in a little bit of tepid water to soften the capsules and then add to the feed or cut the capsules up first with scissors.
Vitamin E capsules can be purchased on Ebay or the many online pharmacy websites or pharmacies or supermarkets. Look for a brand of natural vitamin E capsules that has some oil mixed with the vitamin E rather than just glycerin/gelatin on their own. Can be any oil, safflower oil and soybean oil are commonly used. Vitamin E should be used up within six months or less. Moisture and air (oxygen) are damaging over time as potency decreases with oxidation. Keep out of direct sunlight, heat and keep the container tightly closed.
Note: If you decide to use a commercial horse vitamin E supplement be aware that vitamin E in the form of a powder or solid must be fed mixed with a little oil as one study showed that vitamin E without the oil is far less likely to pass through the intestinal wall and is excreted instead.
Unfortunately vitamin E degrades very easily and is heat sensitive so even if a commercial feed or supplement lists it as an ingredient it can’t be entirely counted. Vitamin E can react with inorganic minerals, especially iron. If there is any organic carrier in the mix, it will also act as a natural antioxidant as fats oxidise and/or bacterial or fungal growth occurs. Vitamin E should always be stored and added separately.
The best way to determine which minerals are deficient or in excess in a horse’s intake is to formulate a custom mineral mix based on the whole intake using a pasture test or hay test, and taking into account any other feeds. Without a pasture and/or hay nutrient test, whichever is the bulk of the diet, we won’t know which nutrients are in excess or deficient or whether mineral ratios are optimised or not to ensure absorption. Learn more about a feeding plan based on data for your horse or horses.
Links may change over time. If a link doesn’t work, search the title in your search engine.
Finno CJ and Valberg SJ (2012) A comparative review of Vitamin E and associated equine disorders
Geyer H, Schulze J. (1994) The long-term influence of biotin supplementation on hoof horn quality in horses
Josseck H, Zenker W, Geyer H (1995) Hoof horn abnormalities in Lipizzaner horses and the effect of dietary biotin on macroscopic aspects of hoof horn quality https://www.ncbi.nlm.nih.gov/pubmed/7556044
NRC Nutrient Requirements of Horses Search=”Cobalt”
Reilly JD, Cottrell DF, Martin RJ, Cuddeford DJ. (1998) Effect of supplementary dietary biotin on hoof growth and hoof growth rate in ponies: a controlled trial
Ross D. (2016) What We Know About Cobalt – And, Worryingly, What We Don’t. Thoroughbred Racing Commentary
Williams CA, Kronfeld DS, Hess TM, Saker KE, Waldron JN, Crandell KM, Hoffman RM and Harris PA. (2003) Antioxidant supplementation and subsequent oxidative stress of horses during an 80-km endurance race