Antibiotics or antimicrobial drugs are effective medications for the treatment of bacterial infections in horses.

Common equine infections requiring antibiotics include infected skin wounds and abscesses, pneumonia, infectious diarrhea, cellulitis, peritonitis and more.

Many antibiotics have broad-spectrum action meaning they act against many different bacteria. Others more specifically target certain bacterial strains. Your veterinarian can determine which antibiotic is appropriate for your horse given their medical situation.

These drugs are not without risks, and they can have adverse effects on horse health when given without veterinary oversight.

Misuse and overuse of antimicrobials are common problems in the equine industry. This has contributed to growing antibiotic resistance whereby bacteria undergo changes that make them impervious to existing antibiotics.

As a horse owner, it is important to understand how antibiotics work, when they should be used and how to properly administer them to your horse.

This article will review antibiotic use in horses, types of equine antibiotics, and how to limit the associated risks for your horse.

Antibiotics for Horses

If you’re a long-time horse owner, chances are you have given your horse some form of equine antibiotic before. You may even have a leftover bottle of oral antibiotics in your feed room.

But reaching for antibiotics every time your horse scrapes his leg can have unintended consequences. These medications must be used carefully to maximize their benefits and minimize risks.

Antibiotic drugs treat bacterial infections in animals by killing bacteria or preventing them from multiplying so the horse’s immune response can beat the infection. [1][14]

Infections occur when harmful microorganisms invade and reproduce in your horse’s body. While beneficial probiotic bacteria help your horse stay healthy, exposure to pathogenic bacteria can lead to disease. [1]

Antibiotics combat pathogenic bacteria, but they can also disrupt the good microorganisms that are a part of the horse’s natural microbiome, potentially causing diarrhea or gut issues. This is one risk of antibiotic use in horses. [12]

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How Antibiotics Work in Horses

Your horse is exposed to a wide variety of microorganisms in its environment. Most environmental bacteria are harmless, but some are disease-causing pathogens. [13]

Your horse has several natural defenses against pathogenic bacteria, including the good bacteria that populate the gastrointestinal tract. Skin also acts as a structural defense and the immune system fights against bacteria that enter the body. [2]

While the immune system can neutralize many bacterial infections in a healthy horse, severe infections may require medical intervention with antibiotics. [14]

Mechanisms of Action

In general, antibiotics work by disrupting biological processes in bacteria to impair their ability to function and replicate.