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November 2024 Newsletter



Tying-up (Exertional Rhabdomyolysis (ER)

Hi All, 


The National Hunt season has properly kicked off now, as I write this have one eye on The Showcase Meeting at Cheltenham and the other writing this.


It's great to see plenty of clients knocking in winners and getting a good start to the new season. Today, I will hopefully give you an insight into a condition that some may be well acquainted with: Exertional Rhabdomyolysis (ER), better known as "tying-up" or “Monday morning syndrome.” I’m probably a bit late with this update as most horses are back in full training but we are still seeing plenty of it. 


What Is Exertional Rhabdomyolysis?

Exertional Rhabdomyolysis is a syndrome characterized by muscle stiffness, pain, and cramping, usually following exercise. It occurs when muscle cells break down, releasing enzymes and proteins such as myoglobin into the bloodstream. These can affect the kidneys and lead to potentially serious complications if not properly managed. ER can occur sporadically after intense exercise, or it may develop as a chronic issue in certain breeds or individuals. Most people will be familiar with the acute form of tying up but its chronic form can also go unnoticed.


Common Symptoms of ER:


  • Muscle Stiffness: Horses with ER often have hard, painful muscles over their hindquarters and back.

  • Sweating and Distress: Excessive sweating, anxiety, or reluctance to move are signs that something is wrong.

  • Muscle tremors and spasms: Horses muscles may visibly shake or twitch 

  • Lameness or Stiff Gait: Horses may have a stiff or uneven gait sometimes appearing lame on one or more legs. At times you may be suspicious of a broken pelvis when they have actually tied up.

  • Increased Heart Rate and or Respiratory Rate: Due to pain and exertion. Horses may appear distressed.

  • Reluctance to Move: Horses may refuse to walk and may stand with a stretched stance due to the pain associated.

  • Colic-like Symptoms: Some horses may show colic signs like pawing, restlessness and or rolling. 

  • Clinical signs of chronic tying up may be mild but are as simple as a lack of energy or a sour attitude towards exercise




What do you do if you think you have a horse tie up acutely? 


  • Ideally stop and take to its stable- allow to relax 

  • Rug up and keep warm in cold weather or hose and scrape off if hot

  • Ensure plenty access to water

  • If they appear very distressed, call the vet as they may need some pain relief, muscle relaxants (high dose Dantrium), fluids and even sedation in severe cases.

  • Box rest for 24 hours followed by low intensity walking exercise for the following 48 hours 

  • Paddock turnout or walking and trotting can keep the horses tipping over until bloodwork returns to normal



Bloods


Even though you can generally diagnose acute tying up episodes with the clinical signs it is always better to take a blood sample to assess the muscle enzymes. The degree of tying up will be determined by the increase in concentrations of the enzymes creatine kinase (CK) and aspartate transaminase (AST), among others. These enzymes are normally found in muscle cells, and are released when muscle cells become damaged during an episode of tying-up. As a result, abnormally high concentrations of CK, AST, and LDH will be measured in the blood. Bloods taken at the time of the episode will see an increased CK- peaks 4-6 hours post episode, followed by the spike in AST which spikes around 36-48 hours.


It takes time for bloods to return to normal and exercise should be kept light until bloods this time. It can take 2-4 weeks for the AST to return to normal. Increasing exercise intensity too quickly will result in worsening the muscle damage.



Management of horses susceptible to tying up:


 Diet :

  • Horses should be fed a diet higher in fats and eliminate as much sugar and starch from the diet as possibly. 

  • Hay is preferred over haylage and in the face of a tying up episode soaking hay with water helps reduce the sugar content 

  • Supplementing feed with oil (vegetable oils- corn oil/ soybean oil at 100ml/100kg) 


Daily Management :

  • Maintain daily routine with feed and exercise- Ideally no day off 

  • Paddock turnout daily 

  • Warm up and cool off on the walker for 30-60 minutes 

  • Avoid extended periods of box rest or inactivity  

  • Mares can be more prone to tying up when in season so take this into consideration when planning exercise intensity  



Supplementation/ Medication:


  • Dantrolene sodium- 1-4mg/kg given 1-2 hours before exercise (should not be given for  prolonged periods as it may result in muscle weakness and can affect liver function)

  • Sedation- Low dose of ACP 20 minutes before riding out can reduce excitation and anxiety

 

 

All the best,


Patrick


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