by Dr. Justin High, DVM
One of the hallmarks of a true show horse is to have a slick, shiny hair coat in the middle of winter. Everyone knows how much work it takes to keep a horse slick and fit in the summer, much less in cold weather, so if you can do that, you can pretty much do anything.
Getting this accomplished at home is one thing, where you can control all the variables, but being able to maintain that look on the road under conditions that are much less predictable or controllable can prove to be a challenge.
Most horseman know what to do when it comes to fitting horses, but knowing why can go a long way to explain the frustration that comes when your methods stop working. Having a good understanding of how a horse’s brain controls this process, and the ways it can be manipulated, will keep your horses looking great all year long.
Circadian rhythms (CR) are based in brain physiology and are very specific regulatory systems that provide a continuous, internal time-keeping mechanism that is able to react and adjust as needed to changing environmental conditions. Our ability to manipulate circadian rhythms is the basis for success or failure when managing hair coats in horses.
Many years ago, research proved that exposure to certain amounts of light for specific periods of time was effective in manipulating circadian rhythms to induce mares to cycle early or to prevent winter hair growth. Depending on whose research you read, it is basically a 100-watt incandescent bulb 10 feet above the floor in a 10-by-10-foot stall that is required to produce a response. This influence spread over 16 hours of the day with eight hours of darkness is what we all go by, but research shows it does not completely control the process.
For example, in seasonal breeders like horses, 14.5 hours of daylight is thought to be stimulatory – but think of it this way. Mares in Florida start cycling about the same time of year that mares in Wisconsin do. In southern latitudes, like Florida, the longest day of the year has about 14 hours of daylight, where the longest day of the year in Wisconsin is about 15.4 hours.
So, photic period is not the single regulatory factor. But the rate of change in daylight length is much faster in the higher latitudes of the North, but it does not produce a faster response than the shorter daylight hours of the South. All this being said, research has yet to prove what controls the signal completely. That is why some folks will light only in the evening or do pulse lighting at night in an effort to manipulate the clock genes identified that do control the response.
As complex as this issue presents itself, there are just a few common reasons for failure. Fundamentally, any change from your normal program at home that is effective is the root cause of a breakdown. At shows, having lights not consistent with the requirements mentioned above is the most common reason. The height at which the lights are placed and the relative intensity are rarely adequate for this process to be maintained, not to mention the fact that show barn lighting often stays on 24 hours a day.
Circadian rhythms are based on a full eight hours of darkness as much as they are on 16 hours of light. Barn ventilation and changes in temperature can affect horses, but knowing the best blanket weight and horse preference are easy fixes. Exposure to changes in your lighting period, regardless of weather over a weekend show will not typically cause a problem, but those conditions extended beyond five to seven days will predictably begin a new hair growth cycle that no amount of blanketing or lighting can stop.
By far, most lapses in hair coat length are results of altered CRs, but a few disease processes can produce similar setbacks. The top culprits in dull, long hair coats are gastric ulcers and equine protozoal myelitis (EPM). Some odd mineral deficiencies, particularly copper (Cu), can produce poor hair quality. Internal parasitism can be a cause, but there are fatter, slick show horses with high worm loads than there are ones with bad hair strictly from parasites.
Fortunately, complex problems can have simple solutions. Go to all possible lengths to maintain your scheduled program when away from home longer than a few days. Easy fix – use 100-watt clip-on lights with a $15 receptacle timer that plugs into a wall outlet. You can instantly correct the time/intensity of show lights and continue your lighting program away from home. Some horses may need to stand tied so as not to be allowed to put their nose down in a corner away from the light.
Another simple fix is not to over blanket your horse. Horses have an enormous reserve capacity to spare heat, and adding heavy blankets will never overcome bad lighting. Using coolers after working horses and allowing them to fully “cool out” before bathing is another smart but often overlooked idea.
No discussion of a horse’s hair coat is complete without mentioning diet. Calorie-dense feeds high in Omega 3 and Omega 6 fatty acids are crucial to conditioned success. Control all the aspects you can and then allow your veterinarian to stay ahead of potential problems like gastric ulcers and EPM that can be unavoidable.
The bottom line is, different people have different programs that can all be successful in fitting show horses. Be willing to change that program based on the individual horse and what works best for each one. If, however, you have one hair up on you, it will take six weeks to correct it with lights, diet and lots of brushing. There are some “quick fixes” like CaCo Copper IV and even arsenic treatments, but nothing is better or safer than lights, and plenty of elbow grease.
Dr. Justin High, D.V.M., is a veterinarian and partner in Reata Equine Hospital in Weatherford, Texas.