The Condition

A major cause of lameness in poultry is wet litter, which results in foot lesions and erosion of the foot pad. The high fat content of partially digested faeces is particularly erosive. Poor housing environments (for example, with high humidity and poor ventilation coupled with insufficient bedding) are contributory factors. Wet litter around water troughs poses a risk.

Long-standing erosions and other skin damage, such as cuts and abrasions, can predispose birds to a deeper infection of the footpad, frequently referred to as bumble foot. Bumble foot is most often associated with staphylococcus infection. This can result in a large ball-like foot abscess.

When infection occurs, synovial membranes in the joints and tendons of the hock and feet become thickened and oedema is seen. Inflammation occurs and a fluid may be produced around the joints and tendon sheaths. Wounds heal on the outside to leave a hard core of pus in the inside. If the condition becomes chronic, fibrous tissue can form around the foot.

Gunnarson et al (1997) showed an incidence of bumble foot of more than 5% at 35 weeks in some flocks reared in aviary systems. Breed differences in incidence have been noted in caged systems (Tauson and Abrahamsson, 1994, Abrahamsson and Tauson, 1995). A Swedish study has shown that white hybrid birds were more likely to get bumble foot (Gunnarson et al, 1997).

Infection in poultry by the bacterium Staphylococcus aureus can also cause swollen hock joints resulting in lameness. This condition is normally associated with young broiler birds and usually occurs between 8 and 16 weeks.