Blue-Green Algae Supplementation for Horses

Supplements are not necessarily benign and can, in fact, prove fatal.

This is a stock photo of blue-green algae powder.

At the 2016 annual Association of Equine Practitioner’s meeting in Orlando, during the Kester News Hour, one of the papers discussed focused on blue-green algae, often referred to as pond scum. Manufacturers of this product harvest it during algal blooms to produce a popular supplement fed to horses.

The journal paper (Mittelman, NS et al, Presumptive Iatrogenic Microcystin-Associated Liver Failure and Encephalopathy in a Holsteiner Gelding, Journal of Veterinary Internal Medication, 2016; 30: 1747-1751) describes a case of an 8-year-old Holsteiner gelding that had received the powdered supplement for two months for “purported hoof health benefits.” Three days before the horse became ill, a new container was used. He was icteric, compulsively yawning, obtunded (dull mental state), and showed mild signs of colic. Serum levels of AST, bile acids and ammonia were elevated.

The University of Pennsylvania treated him for liver failure using lactulose, metronidazole, enrofloxacin and mannitol to decrease brain edema and high ammonia levels, along with intravenous fluids and dextrose. Despite treatment, the horse developed mania – involuntary biting and compulsive circling – and was euthanized two days after admittance. On necropsy, they found a small, flaccid (like a dishrag) liver, which on histology was consistent with microcystin toxicity that caused hepatic failure and hepatoencephalopathy. Five recent containers of the supplement were tested and three were found to contain microcystin, a component of blue-green algae.

The take-home message of this case study is that supplements are not necessarily benign and can, in fact, prove fatal. Horse owners will appreciate your advice about potential dangers of feeding specific supplements. It is always important to obtain a concise medication and dietary history on every patient.

In the pursuit of high-quality medical approaches to equine cases, it helps to look at evidence-based case studies and corroborate findings with laboratory information on blood testing. Prompt diagnoses can make the difference in outcome in many instances. Favorable outcomes are the objective of every practicing veterinarian, and they are instrumental in ensuring client satisfaction and loyalty.

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