There’s no question that B vitamins are essential for your horse. The question is how much of them to feed. Solid guidelines for when they may need to be supplemented, or in what amount, aren’t available.
Most equine supplements contain B vitamins, but usually in amounts that range from extremely high to just enough to be able to include them on a label. Also, while it’s true that excess B vitamins are rapidly eliminated in the urine, it’s not necessarily true that “can’t hurt, might help” applies. The Bs are definitely a problem.
Fortunately, a full-blown deficiency state of B vitamins will produce dramatic consequences that would be difficult to miss. The horse would exhibit severe anemia, neurological symptoms, serious skin disorders and metabolic derangements, even death.
Naturally occurring thiamine (vitamin B1) deficiencies this extreme simply don’t occur. However, because thiamine is essential for the normal aerobic metabolism of carbohydrates, fats and proteins, there’s a lot of room for less drastic effects. Thiamine supplementation is commonly used for calming anxious, jumpy horses. Sometimes it works, sometimes not — in all likelihood being beneficial only in horses that had suboptimal intakes in the first place.
Biotin is about the only good example available showing the difference between levels adequate to prevent full blown deficiencies versus optimal intakes. Several studies have found improved hoof quality with supplementation at 20 mg/day, which is at least 10 times the estimated minimum requirement. Biotin, as well as the other B vitamins, is also essential for healthy skin and hair growth, and the normal turnover of protein and biotin is important for normal insulin sensitivity in other species.
The first step for determining whether a horse needs any vitamin is to know the requirements. The National Research Council recommendations for horses aren’t much help here because there’s so little solid data available. We’ve charted the NRC estimated requirements, and what requirements might be for exercising horses extrapolating from human athletic requirements, as well as good natural sources.
Horses obtain their B vitamins from diet, from absorption of B vitamins produced by the micro-organisms in their intestinal tract, and in the case of niacin can also synthesize their own in the body tissues from the amino acid tryptophan. Healthy horses at pasture are unlikely to need any B vitamin supplementation, even when pregnant, nursing, or growing. An exception to this may be older horses, since the absorptive efficiency of their gut, and the variety of micro-organisms they have, may not be as good as a younger horse.
Horses that are off feed, or with gut upset of any type, or poor appetite and weight gain from parasitism or any other reason, are also candidates for B supplementation. Beyond that, the group most likely to benefit from Bs are performance horses and horses under stress in general (illness, trauma, travel, etc.). Not only do requirements for optimal intake likely go up, the combination of dietary sources and Bs from micro-organisms may not be able to keep up with the demand.
The NRC recognizes a dietary requirement only for thiamine and riboflavin. Since performance horses aren’t likely to be getting generous amounts of the natural food sources of these vitamins, supplementation to at least half of the estimated performance horse needs may be wise. Since niacin is in abundant supply in a variety of common feed ingredients, and can also be manufactured from tryptophan and absorbed from the gut, it’s unlikely to ever be needed.
Same for B12, except possibly in older horses. Pantothenic acid is also in abundant supply in many common feed ingredients. That leaves biotin, folic acid and pyridoxine, which could be suboptimal for the high-requirement groups.
Some commercial grains have B vitamins added. However, this isn’t a reliable source, because many Bs are vulnerable to heating, interaction with other ingredients, or breakdown by organisms naturally present in the environment. Bs are also commonly added to a variety of supplements, including equine vitamin/mineral multis, but this isn’t an ideal situation either for the same reasons as mentioned in grains, and because the shelf life of the vitamins is much shorter than for minerals.
Finding a supplement that contains only B vitamins isn’t easy. It’s even harder to find one that optimize the levels of all Bs. We searched for products that concentrated on B vitamins, with low-to-no other ingredients that could shorten the shelf life and as little iron as we could find. Folic acid and pyridoxine also often came up short in the products we looked at. In addition, all of the products we found were actually weak on biotin.
Horse Tech’s B-Plex was the best biotin at 4 mg/serving, about double the estimated maintenance requirements but well below the therapeutic dose for feet. Biotin is a pricey ingredient, though. If your horse has a problem that might be biotin-responsive, you may want to simply add it separately. That said, except for the biotin, Horse Tech’s B-Plex came the closest to levels we’d like to see for Bs across the board. At $1.18/day (2 lb. container, 2 oz. serving), it’s a little pricey for its potency, but you do get good maintenance biotin levels and the benefits of flaxseed.
For maximum potency, we’d go with either Uckele’s B Complex 3500 (59??/day), Ultra Fire (47??/day) or Su-Per X-Cell (best price at 28??/day). We’d add enough folic acid from a human supplement (available as 1 mg pills, inexpensive) to bring intake up to at least 5 mg/day.