Enzootic Abortion remains the major cause of pregnancy loss in sheep. It has been shown that abortion rates due to the Chlamydophila infection will be between five and twenty five percent. Further losses can be expected from the lambs that survive as the infection will cause damage to the placenta they will not be as well developed as they should be and they are susceptible to other diseases that they have little chance of resisting. Since 1993 there has been a vaccine against enzootic abortion and around five million ewes have been successfully vaccinated against the infection. There has been some publicity in the farming press that this vaccine has now been found to be the cause of abortion in some samples examined by the Moredum Institute in Scotland this winter.

Both Enzovac and CVAC Chlamydia are live vaccines based on the Chlamydia abortus 1B strain of the virus. This does not occur in the sheep flocks but is similar to the strain that is the cause of the infection and stimulates ewes to react against the wild strain. With the advances in identifying DNA it is now possible to identify the exact strain of virus from abortion samples. It was found that five out of thirty five samples contained the vaccine strain of the infection and it has been speculated that the vaccine may have caused the ewes to abort. Schering Plough and CEVA the manufactures concerned are carrying out further investigations. They point out that the published abortion rate in vaccinated flocks is less than two per cent.

It has long been known that ewes that have been exposed to the infection at lambing time will abort their next pregnancy whether they are vaccinated or not and it is the second year of use that you will see the true benefit of the injections. Also it has not been determined if all of the affected ewes were inoculated at least four weeks before the rams were used as recommended. It might be that the wild pathogenic strain and the 1B strain from the vaccine are in some way getting involved together so that the vaccine strain appeared in the samples from the aborted ewes.

These are interesting results and clearly more research will be carried out over the summer now that new tests are available to determine exactly what is happening here. In the mean time it would be better to continue using the enzootic abortion vaccines. They may not be perfect but you need to think of their long term benefit as after only one injection will give protection against the infection for up to four years. We need to look at the abortion rates over this four year period and not just one single year. I will let you know if I learn anything further from these studies.

Intervet have now announced that they are having problems with the production of both of their sheep abortion vaccines this year. Enzovac will not be available until the middle of August and they will not be able to supply Toxovac at all. Intervet are the only company that manufacture a toxoplasmosis vaccine for sheep. It is disappointing that they have not been able to find a reliable way to manufacture it.

It is often thought that permanent pastures with an abundance of spring flowers must be better for live stock than only rye grass and that cows would avoid eating plants that could harm them. This is not the case. Yesterday I saw a cow that is having a severe reaction to sunlight and is in the process of shedding 90% of her skin. Some plants, St John’s Wort is the worst one, can trigger a reaction in a cow’s liver that leaves any unpigmented white areas of the skin sensitive to sun light. This can happen to such a degree that all of the white areas of the skin are rejected. This is what is happening to my patient. It is unfortunate that she is a dairy heifer that is mainly white and that we had a sudden hot spell last week. Once the process in initiated nothing can be done to stop the skin loss. Keeping affected animals inside is essential to stop the new skin from being rejected as well. Eventually new hair will grow and the heifer will be able to graze once more. Photo sensitisation is a strange condition as not all of the animals that eat the plants that cause it are affected. It seems to be a combination of damage to the liver and exposure to sun light.

As far as I know horses do not become sensitive to sunlight because of a reaction to something that they have eaten. Many horses are affected by eating ragwort each year and it is a continuing cause of concern. All parts of the ragwort plant are poisonous, leaf, stem, flower and pollen. It is particularly toxic if it has been cut and incorporated into hay or silage. The plant contains a toxin which will react with the liver to cause inappetance, disorientation and sometimes loss of vision. If a horse has had prolonged access to ragwort it may not survive.

There does seem to be more ragwort about each year. It is important to remove ragwort before it has a chance to flower as each plant can produce as many as 150,000 seeds. In theory the plant should be controlled by the Weeds Act of 1959 but somehow that doesn’t seem to be enforced. Owners of organic farms often seem to ignore the problem completely and little effort is made to control the plant.

Ragwort will struggle to get established in fields where there is an abundance of grass and sheep help to control it as they will eat the growing plants, with few apparent ill effects. When fields are overgrazed by horses the plants can get established in the bare soil and readily spread.

If you spray or cut ragwort it should be removed from fields as it continues to be toxic even when it has wilted and it is better to burn the stems to dispose of them safely.

At last there is a glimmer of hope that DEFRA in England might get around to make a proper effort to control Bovine Tuberculosis.

Jim Paice the minister of agriculture and foods has stated that ‘It is clear to me, and it always has been, that every country in the world that has got on top of TB has done so only after it has addressed the issue of its wildlife. It is not a single solution. What we said clearly in our manifesto is that it is part of a comprehensive package of measures to address TB. We clearly cannot go on as we are. We are getting nowhere, spending large sums of money and we have got to attack it from all sides’

This will be a welcome change of direction. The wheels of DEFRA turn only slowly. Hopefully now we will see a change of policy on badger control so that we can reduce the relentless loss of cattle to this disease.