The Horse

APR 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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18 April 2019 The Horse | Of course, the trick is to diagnose and supplement before that 24-hour window closes, our sources say. If 24 hours have passed, plasma is your only choice. From Birth to Four Months: The Environment Once you've navigated the risky first 24 hours with successful passive transfer, there's not much more you can do. Just let nature take its course, our sources say. By nature, we mean letting the foal get exposed to endemic environmental microorganisms. "You can't have a sterile environment for your foal," Wagner says. "Not only is it more or less impossible in a barn, but it's also not really good for your foal's health. For example, foals need environmental microorganisms to estab- lish their normal gut flora. This, however, does not mean that their environment should be 'messy.' Normal cleaning, good general horse care, and sufficient nutri- ents and a balanced diet are required to keep mare and foal healthy." Be reasonable, Wagner says. Let the foal live a normal life, with access to clean—but not bleach-washed—barns and pastures. Wash your hands before handling your newborn to get rid of any pathogens picked up from whatever you were just doing. But don't scrub yourself obsessively and certainly not between each time you touch the foal during a single visit. The presence of pathogens helps the young immune system develop, says Horohov, by stimulating it. "Initially, these responses are somewhat immature, but over time they become as efficient as those of adult horses," he says. Keeping this in mind, foal managers should make efforts to avoid subjecting their charges to disease outbreaks, he adds. "Knowing that the immune system of the foal is not as mature as an adult also means minimizing the exposure of the foal to infectious diseases," he says. The best thing a breeder can do to ensure good immunity for a foal is to provide foal and dam with a low-stress environment. "Keep herds stable with the same horses in a group, and give them plenty of turnout time within an estab- lished hierarchy," Wagner says. "Make sure they have plenty of hay or grass and good shelter. This welfare-friendly management keeps stress levels low, contributing to good immune system development." Four to Six Months: First Vaccines Continue with the same young foal management techniques after 4 months of age, say our sources. However, by this time, the foal's own immune system is starting to take over, and the effects of passive immunity are disappearing. That makes it time for the foal's first vaccinations, which should occur any- where from 4 to 6 months of age, depend- ing on his immune history. "Vaccination of the foal should begin once the mare's passive antibodies have declined, as these may interfere with the response to the vaccine," says Horohov. "In most cases, this means waiting until the foal is 6 months of age. However, depending upon the mare's vaccination history and the success of passive transfer, this schedule may need to be adjusted." Breeders should work directly with their veterinarians to establish a custom vaccine protocol for their foals, he adds. Four to six months is also about the age that foals should begin their first deworming program, Horohov says. "Recommendations regarding the use of anthelmintics are based on both the ex- posure risk of the foal and the life history of the parasite (e.g. ascarids)," he says. "Immunity to parasites develops slowly and is typically incomplete, so foals are highly susceptible and require monitoring (with fecal egg counts) and treatment—as do older horses." Diseases of Concern: Rhodococcus equi and Clostridium difficile While antibodies usually attack pathogens as they approach cells, some pathogens get inside the cells before the immune system can attack. This requires the body to provide cellular immunity, as opposed to humoral immunity involv- ing antibodies. But cellular immunity is something horses must develop as they age; it can't come from passive transfer. Rhodococcus equi is one such patho- gen. While adult horses' immune systems can destroy R. equi easily and without showing signs of infection, the bacterium can ravage breeding farms, bringing 1- to 6-month-old foals down with severe The Best Defense You can run an IgG test to evaluate a foal's passive transfer status and whether he need supplemen- tal colostrum. AMY K. DRAGOO Foals usually con- sume mares' feces dur- ing the first weeks of life, colonizing the gas- trointestinal tract with good bacteria. Breeders shouldn't prevent foals from practicing this routine." DR. ANGELIKA SCHOSTER

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