Why are Balanced Equine mineral mixes NOT the ‘everything but the kitchen sink’ type?

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 in Further Reading below.

Chromium

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.”

Vitamins

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 main exception is vitamin E, especially for horses that are fed significant quantities of processed feed/hay or are on a workload. See below about vitamin E.

Vitamin A
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 B7
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.

Balanced Equine sells Biotin on it’s own or another option, the HoofXtra mix contains biotin.

Vitamin D
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
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.