I was told to feed a specific mineral supplement when my horse started eating gravel. It contains over 70 different minerals, and one form contains humus, while the other does not. Would you recommend the free-feed granular form with humate
or the powder without humus’ Is there something else you prefer’
Horse Journal Response
Horses are designed to get their minerals from plants, not dirt. The fact that a product contains 70 different minerals is not necessarily a plus. There’s a good chance many of them are not useful to the horse or are potentially toxic.
The term humate is used loosely, sometimes synonymous with peat or humus, sometimes in reference to a byproduct of coal mining. It’s pretty much an intermediate between shale, decaying plant, animal or fecal material and their end product, which is coal. If you have a compost pile in your yard, you have humic acid.
Humate and the humic and fulvic acids are most widely promoted as a growth enhancer for plants. However, a study done by the USDA and published in Crop Science found no benefit. Other studies have found increased uptake of toxic minerals with humate treatment.
We found only three actual studies that involved feeding humate to an animal. Two showed toxicity, a third showed enhanced absorption of iron in baby pigs. Without having properly performed studies in horses, we really can’t say if this type of supplement will have good, bad or no effects but without a full-mineral analysis and safety studies, we’d pass.
My 26-year-old Arab gelding has had moonblindness for about seven years, and it is progressing to the point that I can’t deworm him without pre-medicating or he has painful flare-ups, one which caused him to colic for the first time in 12 years. He is having episodes more frequently now, without triggers. I’ve read vitamins may help. He’s on a number of Horse-Journal recommended supplements, such as spirulina and flax. Maybe it’s not the kind of condition you can do field trials on easily because the flare-ups are not predictable, but any suggestions would be helpful.
Horse Journal Response
If the flare-ups are after deworming with ivermectin or moxidectin, Onchocerca could be the cause of the ERU, or at least one factor. The adult parasite ”hides” deep in connective tissue like the nuchal ligament of the neck. It releases immature larvae (microfilaria) into the blood stream. From there, they can involve the eye. Those two dewormers kill the larvae, causing an inflammatory reaction, but cannot kill the adult parasite. The microfilaria start reappearing in two months according to one study.
A 1987 study in Trop Med Parasitol examined 292 horses between the ages of 15 and 20, from across the United States, and found that 52.4% had microfilaria in their skin, and 18% had them in their eyes.
The reaction to microfilaria dying typically lasts about seven days. Ivermectin does not kill the adults (which can live for 10+ years inside the horse), but it does suppress their microfilaria production for about two months. It’s a good idea to pretreat a horse with a history like this, but definitely not a good idea to avoid deworming for fear of a flare-up. A better strategy would be to deworm at intervals no longer than seven to eight weeks, to make sure the production of microfilaria stays suppressed.
Onchocerca in other species has a bacteria associated with it called Wolbachia. These bacteria influence microfilaria production somehow and killing them with antibiotics stops the parasite from producing the larvae, and the adults die within 18 months. Doxycycline is a particularly good choice for this since it can be given orally long term with low GI risk, and is also active against Leptospira, another organism commonly associated with ERU. One equine study failed to find these bacteria in the equine strain of Onchocerca, but this has not been confirmed by additional studies. Doxycycline is also anti-inflammatory and anti-autoimmune. It’s an option you might want to discuss with your vet if your horse continues to have flares with no obvious trigger.
If you’re looking for an alternative to drug anti-inflammatory treatments, we know of several moonblindness horses that have done well on Uckele’s Devil’s Claw Plus (www.uckele.com, 800-248-0330), which contains Devil’s Claw, Boswellia, grapeseed extract and vitamins B5 and C. Always clear treatments and supplements with your vet.
Looking For E-Se-C
Upon your recommendation a few years ago, I started using Equine Gold’s E-SE-Plus supplement for my Saddlebred gelding, and it has worked great. The results encouraged another boarder to put their horse on it with the same great results. We were ordering a large size and split the costs. Recently, I’ve found it’s no longer available. Do you have another product to recommend’
Horse Journal Response
Select The Best (www.selectthebest.com, 800-648-0950) has a supplement they call Breeders Pack, which contains 745 IU vitamin E, 597 mg C and 1.2 mg selenium per ounce plus some beta-carotene. You would need 2 oz./day of that. You might want to consider moving to a broader-based multi-ingredient supplement like Gateway’s Su-Per Antioxidant with 5000 IU of E, 3000 mg of C and 2 mg of selenium per 2 oz. serving (www. buygpdirect.com, 888-472-2825).