Page 26 - Canada Spring 2019

Carolyn Hammer, Director of the Equine Science Program at North Dakota State University, suggests vaccinating foals ahead of weaning stress, which can lower immunity, so they have a chance to start building their immune system before they are weaned. For recently purchased foals, vaccinate as soon
as possible to ensure protection.
To build immunity, the body must be able to recognize the anti- gen as a foreign invader and create antibodies against it. If the foal already has antibodies (obtained from colostrum), the body will recognize the antigen from the vaccine and eliminate it and won’t mount enough immune response to create more antibodies. The foal won’t build his own protection. “This is called maternal antibody interference,” she says.
“Most foals, if they received enough colostrum from a vacci- nated mare, generally don’t need to be vaccinated until they are 4 to 6 months of age. The actual age you start vaccinating a foal will depend on the vaccine, the
foal’s circumstances, and risk of exposure to that disease—and perhaps when (or if) the mare was vaccinated,” she says.
There is no exact ideal time, but it’s important to avoid vaccinat- ing during a time of stress, such as right at weaning, or when being castrated. A stressed animal is less able to mount a good immune response to the vaccination. “If you are going to castrate a young colt, it’s wise to start him on his tetanus vaccinations beforehand, for instance. Yet often people want to vaccinate, castrate and wean at the same time. It’s better to not do that,” says Wilson.
“It’s ideal to vaccinate before weaning to start the immune process ahead of that stressful time. Most vaccines require one or two boosters after the initial
vaccination,” she says. The rec- ommended schedule for boosters (how far apart they should be) will be on the vaccine label and is also listed on the AAEP website under vaccine guidelines and the chart for foals.
“Recommendations for influ- enza are a little bit different than for the other vaccines in that the maternal antibodies for that viral pathogen interfere a little bit longer than with other diseases. For the inf luenza vaccination,
we really prefer to not vaccinate foals ahead of 6 months of age (preferably 7 to 8 months of age for their first dose) if the dam was vaccinated. Recommendations for foal vaccinations do keep chang- ing, as we learn more about their immune systems and responses to vaccine,” she explains.
26 SPEEDHORSE CANADA, Spring 2019
Before castration, start the colt on tetanus vaccinations. Most people want to vaccinate, castrate and wean at the same time. It’s better to vaccinate ahead of that stressful time, however, as a stressed animal is less able to mount a good immune response to the vaccination.
EQUINE HEALTH