Laura Green from the University of Warwick provided some interesting perspectives from her research into footrot in sheep and the best mechanisms of effectively controlling the condition in real economic conditions. Overall her results show that intervention at the individual level with antibiotics is the best system from both an economic and welfare consideration in terms of reduced incidence, improved recovery and health. A brief summary of the results presented by Laura is given below.
Laura described a number of studies carried out at the University of Warwick funded by Defra to look at control of footrot in UK sheep farms. One study to look at the effect of isolation treatment on incidence found that individual treatment reduced overall incidence from 6-8% to 1-2% and also showed that recovery time was faster in treated sheep. In a further study it was shown that trimming actually impeded recovery, with antibiotics showing the best control of footrot. The study also looked at foot conformation and showed that sheep with poor conformation were more prone to lameness. It could therefore be that foot trimming is preventing feet returning to good conformation which would explain the correlation seen between the number of foot trimmings and incidence of footrot.
The study compared two control systems; intervention versus control sheep, and showed that although more treatments were required in the intervention group (at a total cost of £135) there was an overall benefit of £600 due to fewer days lame, fewer barren ewes and fewer dead lambs, showing an economic as well as welfare benefit to this system. The study demonstrated that lameness can be controlled to less than 2% lame but that more is needed to be done in terms of ensuring that best practice control methods are well implemented. Work is currently underway, funded by Defra, to look into what is required to implement a good intervention strategy and involves clinical psychologists. One suggestion is that it is not always easy to understand where money is made and lost in a sheep farm so elucidating this information could assist farmers to make the best decisions from both an economic and welfare perspective.
Lameness is a nearly ubiquitous problem with around 97% of farms affected with on average 10% of sheep lame. 90% of lameness is caused by footrot, a condition which develops following damage to the foot which leads to interdigital dermitis before forming footrot. It is driven by bacterial infection (Dichelobacter nodosus) in the epidermis. It seems that the bacteria cause disease by dose rather than simple presence on the foot. Footrot has two components; an acute phase which is related to inflammation, and a chronic process which is related to tissue damage and poor conformation. A second bacterium has been implicated in footrot - F.necrophorum but it is thought this comes in once footrot has been caused by Dichelobacter nodosus and increases persistence of the condition.