Stringhalt in horses is a condition characterised by excessive and prolonged flexion of one or both hindlimbs during forward or backwards movement (El-Hage et al, 2017). Horses grazing on pasture heavily infested with flatweed (H. Radicata) and/or relatively poor quality pastures, is usually associated with Stringhalt, however, it is still not completely known whether it is caused by a nutritional deficiency, plant toxicity or a combination of the two.
Stringhalt in horses is divided into two major categories: ‘Australian Stringhalt’ and ‘Classic Stringhalt’. Australian stringhalt is differentiated from classic stringhalt by the severity, occurrence of outbreaks, distinct seasonal pattern and the ability of affected horses to recover spontaneously. It was initially described in Australia and New Zealand but has also been reported in Europe, North and South America and Asia (El-Hage et al, 2017). Classic stringhalt does not typically occur in outbreaks and usually has no obvious cause.
Horses with stringhalt have characteristic, though very variable symptoms. After thorough research and literature, a grading system was developed.
Table 1: Grading of symptoms for stringhalt in horses (Huntington et al, 1989; Domange et al, 2010)
|Only noticeable when horse was backed, turned or stressed
|Slight limb jerkiness when horse moves off at a walk or trot
|Moderate hyperflexion noted when walking or trotting especially when initiating at stopping movement
|Severe hyperflexion with hindlimbs hitting abdomen when backing and turning. Horse is unable to trot
|Hindlimb held hyperflexed for prolonged periods when initiating movement which is characterised by plunging, leaping, hopping motion
|Prolonged recumbency following grade IV-V stringhalt gait
Stringhalt in horses affects the peripheral nervous system. The largest nerve fibres are the primary target for Australian Stringhalt and are found in the horse’s hind legs and the larynx. The hindlimbs show the most obvious clinical signs but some horses will also emit a hoarse roar when they whinny.
Horses with stringhalt symptoms should be removed from their pasture and evaluated by a veterinarian. Away from the toxins, the median recovery period for most horses is 6-18 months, however, mildly affected horses can recover more quickly. It should be noted, that in severe cases, recovery might take over 2 years to complete.
Thiamine (vitamin B1) is an essential cofactor in cell metabolism, production of neurotransmitters that carry messages from the brain along the nerves to the muscle and synthesis of myelin, the sheath that surrounds nerve cells. It has been successfully reported that supplementing vitamin B1 can assist in the treatment and recovery of stringhalt in horses (Huntington et al, 1989). Antioxidants tocopherol (vitamin E) and ascorbic acid (vitamin C) have also been administered to horses in order to reduce oxidative injury to nerve cells caused by the toxins ingested (El-Hage et al, 2017).
Ranvet’s Muscle E contains a blend of vitamin E, thiamine and Choline to ensure optimal muscle health and nutrition while exerting a powerful anti-oxidant effect, playing a role in immune, cardiovascular, circulatory and neuromuscular functions. Ranvet’s Settle’em, Aminovite Plus and Ration Balancer contain concentrated sources of thiamine and Vitamin E to help support healthy levels in your horse’s diet.
Written by Eliza Barton BAnVetBSc Hons
Source: Domange, C., Casteignau, A., Collingnon, G., Pumarola, M. and Prymenko, N. (2010) Longitudinal study Australian stringhalt cases in France. J. Anim. Physiol. AAnimal Nutr. 94, 712-720.
El-Hage, C.M., Huntington P.J., Mayhew, I. G., Slocombe R.F. and Tennet Brown B.S. (2017) Pasture-associated stringhalt: Contemporary appraisal of an enigmatic syndrome. Equine vet Educ.
Huntington, P.J., Jeffcott, L.B., Friend, S.C., Luff, A.R., Finkelstein, D.I. and Flynn, R.J. (1989) Australian stringhalt – epidemiological, clinical and neurological investigations. Equine Vet. J. 21, 266-273.