BY ALEX ASHWOOD
A practical problem for any stud breeder irrespective of breed is to deal with inherited faults in cattle. A further challenge is to correct suspected inherited faults which only become evident due to a combination of factors. Defects of structure and function although not common are a concern to most stud breeders. Spasmodic flexion of one or both hind limbs is termed “stringhalt”. The flexion may be only slightly noticeable or so exaggerated that the mobility of the animal is severely impaired. The tendon of the lateral digital extensor causes interference in the movement of the patella. Initially all that maybe noticed is stiffness of the hind limbs which then leads to a jerky action in one or both limbs and eventually dragging and locking of the hind limbs. Whilst spontaneous recovery does occur, frequently there are intermittent incidences of the disorder. Dorsal luxation of the patella (stringhalt) is the most frequent form of patella luxation. Sporadic occurrences are seen in dairy cattle and it is reported to be quite common with draft bullocks in India.
Stringhalt appears to be an inherited – environmental defect with an extremely variable “expressivity” (ie. strength of phenotypic manifestation). The predisposing causes of “stringhalt” are not known precisely. Suggested causes include inherited factors, physical strain causing ligament damage, low levels of nutrition and production stress and/or a combination of these factors. Obviously any functional defect has economic implications and an increase in the frequency of the disorder can have a major impact on the financial returns and the operation of the stud. Unfortunately, due to the nature of the stringhalt, attempts to eradicate the defect through rigorous testing of the defective gene and/or simulating environmental and other predisposing conditions appear to be out of the question at this point of time.
