Heavy Horse Health Problems
- Mar 1, 2004
Draft horses are enjoying a comeback. Not since the days when they were required to move the nation have the "gentle giants" been so sought after as riding and driving competitors. Draft crosses are found worldwide, competing at many levels and just providing locomotion to those who want a horse with a calmer disposition and greater weight-carrying ability.
When it comes to certain veterinary conditions in horses, size matters. Those gentle giants are predisposed to specific problems (although fortunately, not many). They also require adjusted dosage amounts for certain types of drugs and have somewhat heightened nutritional concerns.
From the Get-Go
The most dramatic differences in veterinary care between draft and light horses concern reproduction. Twinning is very common, and there are multiple challenges in getting draft mares pregnant. Draft stallions tend to have fertility problems, even though their total sperm numbers can be close to those of the light horse stallion, says Scott A. Nebergall, DVM, of The Arthur Veterinary Clinic in Arthur, Ill., a Belgian and Clydesdale breeder and a member of Clydesdale Breeders of the USA and the Belgian Draft Horse Corporation of America.
"The majority of draft stallions produce a large volume of gel in the ejaculate and a larger volume of ejaculate in general," Nebergall explains. "A light horse stallion may have a concentration of 150-400 million sperm cells per milliliter; a draft stallion may produce 70-85 million sperm cells per milliliter. It's like pouring a cup of sugar in a half gallon of water or pouring a cup of sugar into two gallons of water--the concentration is that much more dilute. So, getting an ideal breeding dose can be very difficult."
Draft mares also have their own difficulties. Says Nebergall, "Draft mares can be more complicated to get in foal because of the sheer size of the uterus, retaining fluids, or having larger incidence of endometritis, probably due to previous foaling. They may have had a difficult foaling and passing the afterbirth, and thus a good chance of a bacterial infection in the uterus, leading to problems in conception in rebreeding the mare that year."
Dystocias are a considerably bigger problem, states Nebergall. "The foal is bigger, so delivery is a bit more complicated and labor-intensive for the mare. Because draft foals can be considerably larger, physically correcting a dystocia can be extremely difficult and sometimes impossible. Just because the foals are larger does not necessarily mean the birth canal will be proportionally large enough to correct a malpresentation. We try to be present for as many foalings as possible to help assist the mare and detect any complications early. Extremely complicated dystocias can be avoided if experienced personnel are present when the mare begins to foal."
Michael R. Stone, DVM, is a clinician at Oak Harbor Veterinary Hospital in Oak Harbor, Ohio, and Westview Veterinary Hospital in Fremont, Ohio, as well as a breeder/exhibitor of Belgians for Oak Haven Belgians, national director for the Belgian Draft Horse Corporation, and American Embryo Transfer Society member. He says, "Draft mares are very sensitive to toxemia and high temperatures; a lot of that is due to that really large uterus. After birthing, if you don't get all that blood and placenta out of there, those mares will spike a temp. If you have a draft with a temperature of 103ºF, you definitely don't want to go to bed that night: Someone needs to assist her or she's going to be in trouble. We religiously take temperatures every 12 hours for a good four days after foaling. They can spike a temp, get laminitis, and fall out of their feet. They are very sensitive!"
Because labor can be more intensive, it's fairly common for newborns to be very slow to rise and nurse. "The most common cause of neonatal death is probably starvation," Stone states. "People see the foal with its head up underneath the mare, but he's searching, not necessarily sucking. Once you get them up, foals need a lot of assistance in pointing them in the right direction. That first day, you may be assisting that foal every couple of hours in helping him get up and nurse."
"The reason for the slow start in draft foals is probably due to their size at birth and just fighting gravity. The delivery is probably no more troublesome than light horses, just coordination, strength, and agility in refining their motor skills to nursing and getting around. This does not always happen, but is fairly common," Stone continued.
He tubes the majority of foals at birth to make sure they get adequate amounts of colostrum; Nebergall often recommends manual nursing on a bottle within the first hour of birth.
"Obviously, nursing provides the foal with energy, and the earlier the foal nurses, I feel the quicker the foal gains strength and the ability to get up, stand, and nurse unassisted," Nebergall says. "If the foal appears to have an abnormal suck reflex (a complication called "dummy foal" that occurs due to oxygen deprivation during the foaling process, leading to brain swelling and neurological motor deficits), we immediately treat the foal with intravenous medications to help reduce the swelling within the brain and restore normal motor skills."
A devastating neonatal disease unique to Belgians is an inherited skin disorder known as junctional epidermolysis bullosa (JEB). "JEB causes birth of foals with skin that begins to peel off either before or just after birth, and which can also cause loss of hooves," says Beth A. Valentine, DVM, PhD, associate professor at Oregon State University. "There is no treatment for JEB, and affected foals are soon humanely euthanized."
According to Stone, about 20% of Belgians are carriers. Fortunately, the defective gene has been identified, so selective breeding should be able to eliminate affected offspring. There is a test that is currently run through the Belgian Draft Horse Corporation and then forwarded to the UC-Davis Genetics Laboratory. Hair is submitted, along with the horse's registration papers. Identity is verified and then the status of the carrier or non-carrier is detected, and then the registration papers are marked accordingly. (For more information, see "JEB in Belgian Draft Horses" on page 28.
Big Bones/Heavy Muscles
"Draft youngsters are definitely prone to developmental orthopedic disorders such as OCD (osteochondritis dissecans)," states Valentine, who owns draft crosses and who has worked with draft horses and their owners while researching muscle disease. "Some of this may be due to genetics and some may be the effect of the rapid growth of draft youngsters."
In treating OCD, Nebergall recommends surgical removal of the bone cysts as early as possible to achieve the greatest chance for complete recovery. He says that a fair percentage of young draft horses experience epiphysitis--inflammation of the epiphyseal (growth) plate--again related to fast growth or pushing too hard nutritionally.
"We suggest reducing the conditioning and letting them grow more naturally instead of pushing the growth," Nebergall says.
A problem with adult drafts can be with arthritis (degenerative joint disease, or DJD). "Years of carrying their weight and concussion from working on hard surfaces can lead to a higher incidence of degenerative joint disease, such as high and low ringbone," Valentine states.
Heavily used plow horses, which are still used on Amish farms, can also experience earlier onset of DJD, says Nebergall. "Not utilizing them as frequently or as hard can reduce clinical signs, and NSAIDs (non-steroidal anti-inflammatory drugs) can definitely help relieve the majority of the discomfort of DJD," he says.
Valentine adds, "Good farrier care is also essential. It's not clear whether joint supplements are effective, but they don't hurt. When the horse is sore, pain medications such as Bute (phenylbutazone) can help a lot. Such medications should only be used following your veterinarian's advice, though."
Drafts are often "metabolically different" and thus prone to developing muscle problems, most notably equine polysaccharide storage myopathy (tying-up, or PSSM), Valentine says. "Feeding grain can exacerbate the problem."
Additionally, because a draft's heavy muscling gives him a lower skin to muscle area ratio in which to dissipate heat from working muscles, drafts are at higher risk for overheating. Many thermoregulation, muscular, and orthopedic problems can be addressed or avoided through a diet high in fiber and fat and low in starch and sugar, reports Valentine. "Fat supplementation can help decrease excess heat production during hot weather," she adds.
A neuromuscular disorder seen more frequently in draft horses than lighter breeds is stringhalt. This can present in horses as young as two years, Nebergall says. "In many cases, the horse can remain useful and comfortable despite the disease, although a show career can be halted and field horses may not work with as much efficiency," he explains.
Surgical removal of the lateral digital extensor tendon might provide improvement for some horses.
Not surprisingly, the draft's heavier body weight carried by the hooves and legs can cause increased risk of lameness problems--laminitis, low ringbone, arthritis, and canker.
"The width of the heel is important," says Stone. "You have a lot of weight up above a small surface area, so the bigger and broader we can get that foot, the less problems we have down the road. We do this by genetic selection and proper hoof care."
Most medications--including antibiotics, dewormers, and pain relievers--are given according to the horse's weight. So, while a draft horse would receive a higher dose, the per pound basis is the same. However, vaccines are not administered any differently for the draft horse.
Anesthesia is dosed by weight, but an anesthetized draft does require a little different handling. "Because we're dealing with a much larger animal, we'll use a padded stall and as much manpower as we can get in helping them to lie down," Stone says.
Additionally, Nebergall notes that there is an increased concern for recovery problems in drafts that are anesthetized for a long time. "Recovery is sometimes difficult," he says, "because they run into myositis (muscle inflammation), which is not always seen in the light horse. The problem in draft horses is due to the fact that unique to drafts is a storage disorder or myopathy (PSSM). The best way to avoid myositis is to be as efficient during a surgical procedure as possible and keep anesthetic time to a minimum. Most recommendations are to keep anesthetic time to under one hour, if at all possible."
However, draft horses typically require less sedative than lighter horses. "A lot of that is due to their cold blood and slow metabolism, but also their demeanor," Stone says. "Most drafts are much more docile than the light horse." Stone usually sedates at 50-75% of the recommended dose, letting the horse's nature help determine dosage amount.
A good, balanced diet is especially important for draft horse health.
"There's a lot of bone they're putting down," Stone points out. Draft horse feed proportions are the same as those of the light horse--about 2% of their body weight per day. However, because of the draft's predisposition to myopathies (muscle disorders) such as equine PSSM, Stone says it's important to feed draft horses diets high in fat and fiber and low in carbohydrates (i.e., reduced sugars and starches), with adequate amounts of balanced minerals.
Valentine cautions that when feeding a high-fat and -fiber diet to youngsters, it's important to ensure the horse is not getting so many daily calories that he gets fat or grows too fast.
"A young draft on this type of diet may need a daily supplement to ensure adequate vitamin and mineral intake, as the higher calories of fat will mean a lower volume of concentrated vitamin and mineral fortified feed will be fed," she says.
"Growing horses require more of many of the vitamins and minerals than do adult horses," she says. In general, she recommends feeding plenty of high-quality hay or pasture, a forage-based feed with added fat, and any necessary supplemental vitamins and minerals for draft horses of all ages.
"Vitamin E supplementation--at least 1 IU (International Unit) vitamin E per pound of horse--is also important for any horse not on high levels of alfalfa products or green grass pasture for much of the year," she states.
Like the giant breed dogs that age more quickly and have a shorter life span than their smaller canine cousins, draft breeds might also have a somewhat reduced lifespan. "Their longevity is not very good," Stone states. "For a draft to make it to age 20 is very, very significant. Their life expectancy is probably around 18, although I've seen 24-year-olds. Draft horses can start seeing 'senior' type problems beginning in their early teens, including a decrease in performance and other old age problems such as musculoskeletal disorders, abdominal crises, colic, and cardiac disease."
However, paying attention to a draft's sometimes unique needs and providing prompt veterinary attention can help the draft horse live his life in the biggest, fullest way possible.
VETERINARY INSTRUMENTS FOR BIGGER HORSES
Sometimes bigger horses require bigger veterinary instruments. "I like to use very large hoof testers when doing a lameness exam in order to get pressure on the foot," says Michael R. Stone, DVM, a clinician at Oak Harbor Veterinary Hospital in Oak Harbor, Ohio, and Westview Veterinary Hospital in Fremont, Ohio, as well as a breeder/exhibitor of Belgians for Oak Haven Belgians, national director for the Belgian Draft Horse Corporation, and American Embryo Transfer Society member.
He added that longer endoscopes are often necessary to examine the abdominal cavity. And, he said with a smile, the short veterinarian's best friend is a step stool or a bale of straw for standing on when palpating a draft mare.--Marcia King
About the Author
Marcia King is an award-winning freelance writer based in Ohio who specializes in equine, canine, and feline veterinary topics. She's schooled in hunt seat, dressage, and Western pleasure.
POLL: Radiographs for Hoof Care