So, what does a person look for specifically?
Let's start with vitamins. Water-soluble vitamins to be specific. Water-soluble vitamins are, as a rule, the safest vitamins to supplement because the body simply uses what it needs and sheds the rest. Water-soluble vitamins are the B-complex vitamins and Vitamin C.
When fed as a complex, the B-vitamins generally include;
Thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folic acid (B9), and cobalamin (B12).
Most of your probiotics these days contain the B-vitamin complex.The B-vitamins are manufactured in the horse's hind-gut (cecum and large intestine). As a rule, a healthy horse doesn't really need to have the B-vitamins supplemented, but during times of stress, tummy upset, diarrhea it doesn't hurt to provide some extra support. Hard working horses and horses that get little to no green grass can also be benefited by the addition of the B-complex vitamins.
Many of the B-vitamins are also available individually and used to treat specific issues/problems.
*Red lettering has links attached.
Biotin is the most often individually supplemented B-vitamin and is primarily noted for improving hoof quality. The recommended daily allowance of Biotin is 20mg. Most of the hoof-builder products on the market provide anywhere from 28mg to 50mg. Proving if nothing else, that Biotin is pretty safe to be fed in large amounts. Biotin is most often coupled with an amino acid called methionine and more recently lysine and zinc. Key Players In Hoof Growth. The actual minimum/maximum feeding level of methionine is unknown so when trying to compare products, the methionine level is likely to be highly variable. A horse only requires 175-250mg/d of Zinc (although some reports say up to 400mg/d) and 30-35mg/d of Lysine (another amino acid).
It should be noted that methionine needs B6 to function in the system. There is little evidence that B6 is individually deficient. Deficiency's in B6 is most often related to an overall B-vitamin deficiency which often shows up in horses whose hind-gut health is compromised, they are particularly hard-working or they get little or no green grass. Which of course, leads us right back to probiotics, which often include a B-vitamin complex to help get the hind-gut functioning properly again. Science is proving that poor quality hoof walls and/or laminitic problems are a direct result of what his happening in the hind-gut, which is often a high sugar/starch problem which induces intestinal inflammation and reduces the manufacture and/or absorption of the B-vitamins overall.
There is also evidence that pairing Biotin with Chromium can help stabilize IR/IR-sensitive horses. The reason being is that Biotin plays an important role in carbohydrate metabolism and stimulates liver glucoknase activity, increases insulin production and enhances glucose uptake in muscle cells. Chromium aids in insulin sensitivity. Not sensitivity in a bad way...In a good way. IR horse's bodies have have begun to 'ignore' glucose uptake/metabolism into the cells and chromium reawakens their ability to use and disperse excess glucose. Chromium is actually a mineral, so I will discuss it more in depth in the mineral portion...You guessed it...There is far too much information for one post, so I'm breaking things down.
Chromium Supplementation On Thoroughbreds In Training
If you get nothing else out of the above reference, take this piece of information...EXERCISE is the key to chromium utilization...and is often the key to 'fixing' IR horses. The effects of regular exercise is often downplayed in the 'how to fix' an IR horse. It's mentioned...but the virtues of regular, regulated exercise is often mentioned almost as an afterthought...After prescribed dietary changes and the addition of supplements of course. Regular, forced exercise is to hard to sell to most people. 'But poor Pooky is out of shape and lame, I don't want to force him to exercise'. Tough nuggies...Pooky is 300lbs overweight and he NEEDS regular, forced exercise!!! A supplement isn't going to 'fix' his problem without a little sweat equity.
Thiamine(B1) is another supplement that is often sold individually, or most often seen added to 'calming' supplements. I'll simply post this link, because it has simple straight-forward information...Thiamine, A Contradiction.
B12 (cobalamin) is most often seen in blood builder products and is most often coupled with Iron. There is disparity over how well supplemented B12 is actually absorbed. It's a large-molecule vitamin and it's absorption can be disrupted by other nutrients (potassium, folic acid and Vitamin C). B12 rarely needs to be specifically supplemented on the average horse. Most often it is used on race horses/speed event horses and especially hard-working horses. B12 is often seen in 'natural' pain relievers as well. I can't find anything more than a tidbit here and there about 'why'...B12 is NOT a natural anti-inflammatory. I'm going to go out on a limb here and 'guess' that the reason is for it's blood-building ability and as such it probably helps increase circulation, which in turns helps to break up inflammation. Good sources of B12, without having to specially supplement it, can be found in Brewer's Yeast and Soybean meal.
Folic Acid (B9), while in excess, can inhibit B12 absorption, is still necessary because it does work closely with B12 to promote healthy blood. It is almost never necessary to supplement it though because it is both manufactured in the hind-gut and is found in abundance in green grass. Pregnant mares need more of it, but basically a gestating mare needs more of almost everything and not just more of any one particular nutrient.
B2 (riboflavin), B5 (pantothenic acid) and B6 (pyridoxine) fall pretty much into the same category as folic acid. A horse's body manufactures them and/or obtains them from high fiber diets. Supplementing them specifically is not necessary.
Niacin (B3) -Is also seldom seen as an individual supplement, but is often present in higher levels in immune builder supplements and because of it's stability is often added to fortified feeds. There should be no reason a normal, healthy horse would need to be niacin supplemented, but the use of it in immune builders is common because niacin in higher doses does provide vasodilation...and that can also cause a niacin 'flush,' an uncomfortable tingly, burning sensation on the skin and that may lead to a horse looking/acting more 'energized' until the flush fades. Niacin can promote a feeling of 'well-being'. Since a horse's body can manufacture niacin on demand (out of tryptophan), it doesn't particularly store this vitamin and therefore will quickly shed any excess from the system. This makes over-supplementation unlikely.
One of the most common 'calming' agents on the market today is Tryptophan. Some people say it works great, some say not so much. The thing is, tryptophan is turned to niacin in the horse's body, but that transition also requires the input of thiamine, riboflavin and Vitamin B-6. If the horse is deficient in any (or all) of these vitamins, the conversion does not take place and that sense of 'well-being' that an increased level of niacin can provide does not happen. That is probably the key to why is sometimes doesn't work and it would be my guess the horse is (overly or unnaturally) excitable because it is lacking in B-vitamins overall and would probably benefit from the addition of a B-vitamin complex to help balance metabolism and glucose levels.
It is suffice to say that, the majority of horses, especially those on a quality high-fiber diet (hay and/or grass) usually does not need to have the B-vitamins supplemented, but there is sufficient evidence that the addition of them is not harmful to horses and in cases of a compromised or hard working horse, it can be very beneficial. I have never supplemented a specific B-vitamin personally, so I cannot attest to how beneficial that would be, although there are plenty of people who swear by Biotin, B1 and B12.
Vitamin C is the other water-soluble vitamin. As a rule a horse will manufacture and store all the Vitamin C it needs in it's liver. That may not always be the case in a hard-working or older horse. Vitamin C manufacture slows down as a horse gets older and a hard-working horse may not be able to produce enough Vitamin C to keep up with it's needs.
Vitamin C (Ascorbic Acid) has long been touted (in humans and horses) as an exceptional immune booster and free-radical scavenger. So it is often seen in immune boosters and is particularly useful to use around times of stress. It helps prevent cellular damage and is particularly useful for the treatment of respiratory ailments like asthma (heaves) and COPD. That is not the extent of Vitamin C's capacity though, it also supports the synthesis of collagen, which helps support tendon, ligament and joint health, which is why you will often see it included in joint health products these days. Lower doses of pure Vitamin C are rarely troublesome for horses, however higher doses may irritate the hind-gut (It is an acid and can change the pH in the hind-gut), however Ester-C is a buffered, pH-neutral form of Vitamin C that should not cause this problem. There is no specific dietary minimum/maximum for Vitamin C. A supplement product may have a few hundred mg or 1,000mg or more.
I am able to kill 2 birds with one stone in this case, with Moon. Vitamin C helps his breathing tremendously and the joint supplement that works for him contains 1,000mg of it. It was an unintentional discovery, but a good one.
Okay...That's it for the water soluble vitamins. I'm including this article, written by a real veterinarian for those of you who prefer more academic literature.
Vitamin Requirements In Horses
I'm not exactly sure when the above reference was published, although one of the references is from 2000, so it may be as recent as the last decade.