Tying-up is a syndrome which has many potential causes. In recent years, some common beliefs about tying-up have been proven wrong by scientific research. It was once thought to be solely an issue of lactic acid build-up in the muscles, but we now know the syndrome is actually a lot more complex than once first thought.
Typical signs of tying-up include :
- Reluctance to move
- Rapid heart rate
Recent studies have indicated a common cause of tying-up in thoroughbreds is a genetic abnormality in the way calcium is regulated in skeletal muscle. Young, nervous, highly strung fillies are most commonly affected. Studies at the University of Minnesota have found that the disease may lie dormant until certain factors trigger the malfunction of calcium regulation. These triggers may include stress, excitement, lameness and high grain diets. Diagnosis of tying-up is based on the clinical signs and a blood sample to measure the levels of muscle proteins : creatine kinase (CK) and aspartate transaminase (AST). When muscle cells are damaged, they release these proteins into the bloodstream within hours and measuring their levels can determine how much muscle damage has occurred. Prevention of tying up in these horses includes :
- Minimizing stress
- Adhering to a daily exercise regime (turnout, lungeing, riding)
- Reducing grain in the diet and adding additional calories in the form of fat
- Some medications may also help.
- Avoid stabling horses on rest days. You should provide turnout where horses can move freely on days when they are not in training.
- Ensure you include a vitamin and mineral supplement (especially Vitamin E and Selenium) as well as electrolytes to your horse’s feed.
Another form of tying-up is known as polysaccharide storage myopathy (PSSM). Type 1 PSSM commonly occurs in Quarter Horses, Warmbloods and Draft horses. It is caused by a genetic mutation in the glycogen synthase gene. Horses with PSSM store abnormally high levels of glycogen in their muscles. Signs are typically associated with tying up and include muscle stiffness, reluctance to move, firm muscles over the hindquarters, sweating and increased CK in a blood profile. Signs of PSSM1 are usually seen when horses commence initial training or after a period of rest when they have been confined to a stall or small yard.
Treating PSSM involves eliminating grain from the diet and feeding fats such as rice brain or vegetable oil for energy. Horses with PSSM should be turned out as much as possible and long periods of stall confinement should be avoided. PSSM1 is an inherited condition. It is an autosomal dominant trait which means that only one parent needs to pass the genetic mutation to its offspring for signs of tying-up to occur. The presence of PSSM1 in Quarter Horses was shown to be highest in Halter bred horses with approximately 28% of these horses testing positive for the PSSM1 gene.
If your horse is showing signs of tying up, here are suggestions of what you should do :
- Stop exercising the horse and return it to its stall
- Do not force the horse to walk
- Call your veterinarian so that appropriate pain relief can be administered
- If the weather is cold, then place a rug over the horse
- If the horse is dehydrated due to excess sweating, provide small, frequent sips of water to the horse if its hot. Allow free access to water once it has cooled.
- Remove grain and hard feed and only provide hay until signs have subsided
- Once the horse is able to move freely, turn the horse out to small paddock.
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