Feet – DNA testing for susceptibility to foot diseases – foot structure
Sound feet have always been considered vital at Kikitangeo. In the period prior to 1960, foot problems were treated via trimming, treating foot rot and scald and regularly putting the whole flock through a footbath. The conventional thinking at that time was that foot problems were caused by diseases and therefore treatment was the only solution. However, at this time, we found that some strains of sheep (by different sires) were more susceptible than others. With this realisation, the policy of treating foot problems was abandoned, and it was decided to adopt a strict programme of selecting sires with the best shaped feet that were free of foot diseases. At the same time, ewes were not treated and if they did not ‘self cure’ from footrot and scald, they were culled. Within a decade, a major time consuming problem became a non issue. Occasionally, an outbreak of footrot or scald will occur, and in most cases they will self cure via the immune system.
In a DNA test was developed by Dr Jon Hickford and his team at Lincoln to measure the degree of resistance-susceptibility to foot diseases. This test gives a 1-1 for the most resistance, with a 5-5 being the most susceptible. These double figures come, one from the sire and the other from the dam, but scientists are unsure which is which. An average score would be 3-3. When this test became available, we sent blood samples from all our ram lambs to have them assessed. It is understood that the laboratory staff at Lincoln were in disbelief, as about half the lambs had a score of 1-1. Dr Hickford enquired as to how this excellent result was achieved, especially as we had not been involved in the years of research to establish this DNA test. Dr Hickford was told that it was ‘the result of 50 years of selecting the best and culling the worst’.
What was of particular interest was that one sire, KIKI 765-98, had 22 sons out of a total of 25 with foot scores of 1-1. This is the same sire that was so dominant for worm resistance. This was mentioned to Dr Hickford as there could be a possible link between worm and foot disease resistance. However, this situation could have been purely coincidental. To his credit, Dr Hickford researched the subject and found that there was indeed a link between these two traits. His finding was that sheep most susceptible to foot disease – those with scores of 4’s and 5’s were more susceptible to worms. This finding was no surprise to us at Kikitangeo, as both these problems are controlled by the immune systems. Dr Hickford is now saying that animals that are resistant to worms could well be resistant to other disease and parasite problems.
The structure of the foot and how it makes contact with the ground is as important as the DNA test. Ideally, the foot colour should be slate grey rather than jet black. The darker the foot the harder it becomes. Jet black feet are very hard and can be prone to cracking. White feet are much softer and are generally considered less desirable. However, we have found that such light coloured feet have no real problem with foot diseases. Hoof growth should be minimal and surplus hoof should break away. Excessive hoof growth – often called ‘snow shoes’ – is a strongly inherited trait and sheep with this fault must be culled. Hoof shape should be roughly oval with straight sides. The bonding between the ‘sole’ of the hoof should be well bonded with the ‘upper’ hoof. All these attributes have been selected for at Kikitangeo and this selection practice should be ongoing. All rams offered for sale have their feet carefully assessed and given a grading.