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Blue-Green Algae for Horses

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While natural foods are typically best for humans and horses alike, not every naturally occurring substance is 100 percent safe. Blue-green algae, or BGA, for horses has proponents and detractors, which causes confusion. If your horse has a specific affliction, your veterinarian may advise BGA or he have another solution that’s safe, effective and free from controversy, so include him in this decision-making process.

Blue-Green Algae

If someone tells you that blue-green algae organisms, or cyanobacteria, are as old as the earth, believe him. But other than respecting its age, it’s tough to be a fan -- BGA is slimy, and it smells. BGA can live in saltwater and freshwater; some varieties grow under controlled conditions to eliminate contamination that occurs in the wild. Advocates of BGA for both horses and humans are typically referring to the Aphanizomenon flos-aquae variety, or AFA. This BGA is a freshwater algae that grows only in nature. Upper Klamath Lake in Oregon is the only location in the United States where it grows in large enough quantities for harvesting.

Purported Benefits for Horses

Proponents of BGA as a horse diet supplement cite numerous benefits, from dense vitamin and mineral content to detoxifying your horse’s system of harmful substances such as fertilizers and pesticides. Holistic equine veterinarian Madalyn Ward of Fischer, Texas, has long touted the advantages of BGA and considers it to be the ideal whole food supplement, particularly for horses that consume more hay than pasture grass, since hay loses much of its vitamin content over time. She and other advocates cite BGA’s positive effects on hooves, coats and immune systems. Some users claim to notice their horses have more positive and willing attitudes when in training, and appear to focus better.

Blue-Green Algae Concerns

As of 2013, no scientific research existed that proves BGA is beneficial to horses or that it is harmful. Your biggest concern should be the potential for toxicity; since not all BGA produces toxins, scientific testing is necessary to know which contain toxins and which don’t. Critics cite the presence of microcystins, very harmful bacteria that can cause serious health issues including liver damage and potentially death. Since AFA is the most common BGA and it grows only in the wild, there is no way to know if this and other toxins are present unless you are confident that the supplier or seller tests it. The U.S. Food and Drug Administration reports that most BGA tests positive for some toxins. In 2008, Professor Daniel Dietrich of the University of Konstanz in Germany reported similar results from his testing.

Deciding to Use BGA

You should feed BGA to your horse only if you are confident of the source and that it has been tested. Professor Dietrich noted that U.S. and Oregon health officials believe the average, healthy adult human can ingest 2 grams -- approximately 1 teaspoon -- of microcystins a day without ill effects. Dr. Ward recommends one-half to 1 teaspoon daily for your horse, so talk to your vet about whether he believes the additional weight of your horse mitigates potential negative effects. Also, since BGA is known to cause problems in pregnant or nursing women and exacerbate some pre-existing health conditions, you and your veterinarian should weigh whether these issues might apply to your horse. Dr. Ward suggests that you “listen” to your horse's actions: If he won’t eat it, don’t feed it to him.