Introducing a New Horse to the Herd

With a new partnership to form, getting a new horse can be exciting and rewarding. But how will your new horse’s herd mates take to him?

In a perfect world, every new horse would arrive with a complete medical history, be appropriately dewormed, up to date on all necessary vaccines, and declared healthy by a veterinarian. However, in reality, we know this doesn’t happen. Sometimes we simply don’t know much about a horse’s medical history or background, so applying a strict quarantine procedure is necessary when introducing a new horse to the herd.

There are many different ways to implement quarantine in a barn, and how you do it most often depends on the design of the premises. Some larger barns, particularly busy boarding and show stables, may even have a specific stall or paddock used only for quarantine. Here are some guidelines for preparing for your new horse.

1. Location
While in quarantine, the new arrival should not be in direct physical contact with the other horses. A stall at the end of the barn is suitable, ideally with an empty stall between another horse. Likewise, a small paddock separate from the main pasture that doesn’t share any fence lines is adequate as well. If your barn is lacking space, you can create a temporary holding pen by using a simple round pen if you have one, or even use the riding ring for a short duration.

2. Time
The length of the quarantine period is based loosely on general incubation times for diseases. Since incubation times vary depending on the infective agent, you can only get a rough estimate based on either the horse’s known history or what you might expect his unknown history to be, and if he seems to be healthy.

All new horses, even ones with complete medical histories and up-to-date vaccines need to be in quarantine for some length of time. Keep in mind that for a healthy horse, quarantine is used basically as a holding pen, where you are isolating the horse while you wait to see if he is going to become sick. For a horse that is up to date on vaccines and has received a clean bill of health from a vet, the quarantine can be short—roughly one week. If the horse is not up to date on vaccines and/or came from a questionable, stressful environment, a quarantine period of at least 14 days should be implemented. Some farms, like large breeding farms with young stock, may implement longer quarantines.

3. Rules of Engagement
Even the most well-designed quarantine facility is only as good as the people who operate it. The new horse should be the last one to be fed, groomed and ridden, and to have his stall cleaned. This is to prevent transmission of disease via fomites (any inanimate object capable of carrying infectious organisms, such as tack, brushes and buckets). The new horse should not share tack, grooming supplies or buckets with other horses during the quarantine period. If people must interact with the new arrival before attending to another horse, they should wash their hands and make sure their boots are relatively clean.

4. Vaccinations and Deworming
A handful of the most common infectious agents cause the most problems. Internal parasites; common viruses such as rhinopneumonitis (equine herpes virus 4), influenza, and rotavirus; bacteria that cause strangles (Streptococcus equi), potential diarrhea (Salmonella spp.), and pneumonia (Rhodococcus equi) are the most common infectious agents spread by newcomers.

If you are unsure about the vaccination history of your new horse, the time to vaccinate is during at the start of his quarantine period. Talk to your veterinarian about what vaccines are appropriate for the horse’s age, risk status and geographic location. This is also the best time to deworm the horse. Ideally, your vet should perform a fecal egg count from a sample of the horse’s manure to see what specific worms he has and pick the most appropriate dewormer to use.

5. Meeting the Herdmates
Once your new horse has passed his quarantine period, it’s time for him to get acquainted with his new herdmates. This can be a stressful adjustment as the herd’s social ladder is re-organized. Whether this goes smoothly or roughly is primarily determined by the personalities of the horses involved. However, there are some things you can do to help make the process go as easily as possible.

First, volunteer one of your most easygoing horses to be the newbie’s wingman. Introduce these two horses in a pasture of their own and let them figure out who is alpha in the relationship. Leave these two horses together for a few days so some basis of familiarity can be established. Then, add another pasturemate to the mix and proceed as before. Depending on how big the herd is, this group of three can then be returned to the full herd. If things are still a little shaky, sometimes adding a fourth horse to this small group before releasing them back into the herd can help.

When it comes time for the new horse to make his grand entrance to the herd, be prepared for some vocalizations and displays of aggression. This is normal herd behavior and is necessary for the redesign of the social ladder. It is often scary to watch horses threaten each other in the field, but most of time it’s all for show and rarely do physical blows occur. If this does happen, do not enter the field to break them up. Wait until the incident is over and re-assess. Has dominance been established or does it appear that things are still unsettled? If the latter is true, this may be an indication that the new horse should return to his initial smaller group for a while longer.

There is the possibility of the new horse incurring some superficial cuts and scrapes for the first few weeks. Keeping some antiseptic wound cleaner on hand is a good idea, as is giving your horse a thorough groom every day when he comes in from the field to catch minor wounds before they become infected.

You can also introduce your new horse to his stablemates by taking him out on group rides, either on the trails or in the ring. Putting him in a stall or paddock closer to the others after quarantine will also help with herd integration.

Introducing a new horse to your barn is an exciting time. With some basic knowledge of equine disease and behavior, you can help make introductions go as smoothly as possible.

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