Pain associated with locomotion will generally modify the gait of an animal. This may be restricted to one limb or may involve more than one limb. Lameness can be graded using various scoring systems e.g. Manson & Leaver, 1988 [9 point scale]; Wells et al 1993; Welsh et al 1993; Sprecher et al 1997 [5 point scale].
Non-painful causes of lameness should be ruled out and in companion animals this may be achieved by noting the effect of local, regional or systemic treatment with analgesic or anti-inflammatory drugs. This technique is rarely used in farmed livestock. most lameness is associated with infection (foot rot in sheep or foul of the foot in cattle) or trauma (sole ulcers in cattle).
Changes in gait characteristic for particular pains may be recognised in different species, these gaits may be described using particular terms e.g. careful, stilted, shuffling. Systematic description and analysis of such terms could make lameness assessment more repeatable between individual assessors. By adopting such gaits the animal may be attempting to minimise the pain and promote healing.
Many lame horses may be sound at the walk, only showing an abnormal gait when trotted or cantered. The presence of a rider on-board may also influence the gait of a horse. Many instances of lameness in horses are subtle and may only appear as a reduction in athletic performance. Both 5 and 10 point scales are used to assess lameness in horses. Video examples of lame horses (not lameness scored) can be found on a cd with a book by Ross & Dyson, (2003).
Although the majority of lameness in cattle, sheep and horses is due to problems in the foot (90% in cattle, 85% of which occur on the hind-feet) and injuries to the limbs, damage to other tissue may affect gait e.g. mastitis, large udders in cattle and damage to back tissue (particularly in horses) often presenting as an un-level gait.
Example of the five point scoring system used by Sprecher et al 1997 to assess lameness in cattle with additional information added from Manson & Leaver 1988 and O'Callaghan 2002, could also be used for sheep.
Lameness may affect the 'normal' behaviour pattern of individual animals e.g. more lying down, less eating (or grazing on knees), shorter standing bouts. However, changes in the 'normal' behaviour pattern of the animal may only be noticed after long periods of observation unless the carer is extremely familiar with the individual animal.
Score 1 (sound) The animal walks and stands with a level back and has a normal gait (tested here at the trot in horses) - the hind-feet in line with the corresponding fore-feet, no shortening of the stride or nodding of the head. There is minimal abduction / adduction. Weight is generally distributed evenly on all limbs when standing still.
Score 2 (mildly lame) The animal stands with a level back but may adopt an arched back while walking. The gait may show some abduction / adduction or other slight abnormalities, which may be exaggerated by manipulation of the limb.
Score 3 (moderately lame) The animal may adopt an arched back while standing or walking. Its gait is affected and is best described as short striding with at least one limb.
Score 4 (lame) As for score 3, plus the gait is more severely affected the animal deliberately taking one step at a time. Weight may be taken off one or more limbs/feet (favoured) when standing. The animal has more difficulty turning.
Score 5 (severely lame) The animal shows an inability or extreme reluctance to bear weight on one or more limbs and may be reluctant to rise (if lying) or move (if standing). The animal may stop frequently.
PREVENTION IS BETTER THAN CURE - good quality, clean, dry walking tracks and gateways, appropriate footbath use (copper sulphate, formalin or zinc sulphate), correct foot trimming and culling persistently lame individuals helps prevent many instances of lameness in farmed livestock.
When assessing welfare of a herd/flock the number of affected animals, severity of the lameness (pain), and their on-going treatment should be taken into account.
Further information on lameness of cattle can be found on a CD by R.D. Murray and Z. Woldehiwet (Liverpool University) titled "Lameness in Dairy Cattle associated with Fusobacterium necrophorum infection" produced by CLIVE.