Tying Up

Feeding Horses and Ponies prone to Tying up

Horse canteringTying up, azoturia, Monday morning disease, set fast, or the more scientific name equine rhabdomyolysis syndrome (ERS) are all terms used to describe, typically exercise-associated, muscle damage in horses that has a variety of causes. The clinical signs include muscular pain and cramping usually during or after exercise, or a history of poor performance which also can be a main presenting sign. Although exertion is not always involved, most episodes are triggered by exercise and therefore this condition is often termed equine exertional rhabdomyolysis.

Despite the fact that there is no single change or set of changes that can guarantee you will prevent further episodes, appropriate management of horses prone to the condition, including close attention to nutrition, may help reduce the likelihood, severity or frequency of future episodes.

There have been some major advances recently in our understanding of the condition and a few specific causative genetic defects have been identified. It has been suggested that there are two main sub-categories of ERS and episodes may occur intermittently or recurrently in either group.

  • Those horses with a primary underlying susceptibility that is intrinsic to the muscle which currently can be further sub-divided into:
  • A disorder in muscle contractility or excitation-contraction coupling which is often referred to as recurrent ER (RER: Mickelson and Valberg 2015)
  • A defect in carbohydrate storage and/or utilisation referred to as Polysaccharide Storage Myopathy (PSSM: Valberg et al; 1992; Valentine et al. 2001)
  • Those horses that don’t have an intrinsic muscle defect (or in some cases the specific intrinsic defect has not yet been identified). This group includes those animals that develop this condition due to overexertion and possibly dietary mismanagement.


  • How diet may increase the risk of tying up (in particular the non-intrinsic type)

    Diet and dietary management are amongst the factors that can increase the risk of an episode;

      • Exercising after a period of overfeeding and under-exercising such as after a weekend off.
      • The overfeeding of non-structural carbohydrate (NSC i.e starch and water soluble carbohydrates[WSC]) especially when coupled with a lack of fibre/forage
      • Electrolyte imbalances either down to the diet or an animal’s individual metabolism
  • How you can help (excluding PSSM – for specific PSSM advice call the WINERGY Equilibrium Careline)

    The trigger factors may be different in each horse and therefore an individual’s tolerance of certain dietary factors may be different. However, as diet is one aspect of your horse’s management that you can influence it is advisable to follow the tips below;

    General Management advice

      • Provide as much turnout as possible but manage access to grazing in a similar way as you would for a laminitic in order to avoid a large intake of WSC (simple sugars plus fructan).
      • Maintain a regular exercise programme, avoiding prolonged periods of box rest wherever possible.
      • Take care to warm up and cool down properly before and after exercise.
      • Aim to reduce stress wherever possible including during exercise, turnout and transport.
      • Do not feed in anticipation of an increase in workload – wait until additional energy is needed before increasing intake.

    Dietary advice

      • Maximise forage intake feeding a minimum of 15g per kilogram bodyweight (dry matter) bodyweight per day
      • Soaking hay to reduce WSC may be helpful (Longland et al 2014). Alternatively consider having your forage analysed.
      • Provide a balanced supply of vitamins, minerals and quality protein by feeding the recommended ration of an appropriate compound feed or balancer.
      • Additional vitamin E and selenium may help to support muscle health and reduce the risk of tying up. Daily intakes of 1500-2500 iu of vitamin E and 1.5-3mg of selenium for a 500kg horse in work have been suggested (Saastamoinen and Harris 2008).
      • Vegetable oil can be added at up to 1ml per 1kg of bodyweight per day to provide additional energy (calories) if needed.
      • Add any additional oil gradually (ie increase by approximately 100mls over each week as required) and ensure the diet provides an additional 100-150iu of vitamin E for every 100mls of oil added (Stratton-Phelps et al 2003).
      • The amount of starch that can be tolerated varies between individuals, but start by choosing a feed containing less than 15% starch.
      • On rest days reduce feed intake by half from the evening before to the evening after.
      • Maintain electrolyte balance
  • References
      • Mickelson, J.R. and Valberg, S.J. (2015) The genetics of skeletal muscle disorders in horses. Annu. Rev. Anim. Biosci. 3, 197-217
      • Valberg, S.J., Cardinet, G.H. III, Carlson, G.P. and DiMauro. S (1992) Polysaccharide storage myopathy associated with recurrent exertional rhabomyolysis in horse. Neuromuscul. Disord. 2, 351-359
      • Valentine, B.A., Van Saun, R.J. and Thompson, H.F. (2001) Role of dietary carbohydrate and fat in horses with equine polysaccharide storage myopathy. J Am. Vet. Med. Assoc. 219 1537-1544.
      • Longland, A., Barfoot, C. and Harris, P. (2014) Effect of water temperature and agitation on loss of water-soluble carbohydrates and protein from grass hay: implications for equine feeding management. Vet. Rec. 174, 68.
      • Saatamoinen, M.T. and Harris, P.A. (2008) Vitamin requirements and supplementation in exercising horses. In: Nutrition of the Exercising Horse, Eds: M.T. Saastamoinen and W. Martin-Rosset, EAAP Publication No. 125, Wageningen Academic Publishers, Wageningen. pp 233-255
      • Stratton-Phelps M., Fascetti, A.J. and Geor, R.J. (2003) Nutritional support in selected metabolic, hepatic, urinary and musculoskeletal conditions. In: Current Therapy in Equine Medicine, 5th edn., Ed: N.E. Robinson, W.B. Saunders, Philadelphia. pp715-722.