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This month’s super installment sees us explore the topics of both bovine immunity – a topic so interesting that it has been picked up on by both of our Farm Editors – and mud fever in horses.
Cows with high levels of disease resistance soon available to farmers
Emma Plowright (Farm News Editor)
The company Semex have recently announced that sires that have been proven to have high levels of immunity will soon be available for farmers to purchase. When these animals are bred, there is a 25% chance that the trait will be passed on to the offspring.
Research suggests that cows with a high immune response are ‘two to four’ times less likely to contract diseases such as mastitis, metritis, ketosis, retained placenta and Johne’s disease than those with a low immune response.
According to Semex, this “marks a significant breakthrough in improving disease resistance in cattle which will reduce the use of remedial medication”. Trials have shown that the use of these sires can significantly reduce disease levels in a herd. Not only will less need to be spent on drugs and medical attention, there will also be fewer losses due to lack of productivity. It is estimated that the resulting reduction in disease could be worth around ‘£50 per cow’
The testing for high immune response involves blood samples, skin thickness tests and immune system stimulating tests similar to vaccinations. The process takes around two weeks and it is only necessary to carry out the test once during a sire’s lifetime.
This test will be exclusive to Semex for the next ten years.
A new trait in cows: high immunity
It is a known fact that one of the many problems dairy farmers face is that of diseases such as mastitis and ketosis. Semex, a company that deals with cattle genetics, has recently made public that the new trait, ‘Immunity+’ will be available soon for customers to use when breeding their cattle.
This comes after researchers at the University of Guelph in Canada were able to measure the immune response of a cow and thereby label a cow as ‘high immune response’ or ‘low immune response’. They did this by taking blood samples and doing skin thickness tests, and measuring the antibody and cell-mediated response by stimulating the immune system in a similar way to how a vaccine works. Those with a high immune response, ‘HIR’, are thought to have ‘a more balanced immune response capable of defending the cow against a more diverse range of pathogens’. Currently, it is thought that around 10% of bulls have genes that are classed as HIR.
The application of this experiment has proved to be very useful when selectively breeding cattle for desired characteristics. The researchers estimate that cows with HIR are 2-4 times less likely to contract a disease than those with LIR. They also discovered that this trait for high immunity has a large chance of being passed on – 25% – considerably larger than the percentage for other traits, such as calving ease, which stands at 6-7%.
So what is the benefit for the farmer? Well, bulls with the trait are shown to have higher levels of response to several diseases, including mastitis, metritis, ketosis, retained placenta and Johne’s disease. If this trait were passed on to offspring, then this would save the farmer money as it reduces the need for medical intervention. Managing director of Semex, Gordon Miller also states that the savings might be worth £50 per cow. From a welfare point of view, less disease will increase animal wellbeing, which will increase milk quality and quantity.
What’s more, on a grand scale, it would certainly be more beneficial for us to work with cows that have higher immunity, with antibiotic resistance becoming an ever growing problem, this may be an excellent, non-invasive help to the issue. It also avoids controversies surrounding genetically modified animals, as farmers would purely be choosing to breed from a cow with more desirable characteristics. Clearly, there is not a 100% chance of the trait being passed on, but this new characteristic may certainly be a step towards a future that sees healthier dairy herds across the county.
‘Genetic and epigenetic regulation of the bovine immune system: practical implications of the high immune response technology’ (BA Mallard et al)
It’s that time of year again; horse owners all over the country are pulling out their wellies and braving the ankle high mud that borders most horses fields in winter. Unfortunately with mud comes mud fever or pastern dermatitis; a range of skin reactions triggered by cold wet weather that causes scabs to appear typically around the heel area. In severe cases the skin can split open leaving deep cracks where bacteria thrive causing painful legs and lameness.
As in a lot of human bacterial diseases, antimicrobial resistance due to overuse has become a real issue when prescribing treatment for mud fever. A study from the University of Liverpool found that 80% of vets used antimicrobials such as trimethoprim-sulphonamide to treat infected limbs. These are the most popular treatment to use as they are easy to administer and inexpensive, however due to increasing resistance this is sometimes not an effective treatment. Therefore good management is recommended to keep the condition at bay.
Firstly horse owners suspecting mud fever should consult their vet to obtain an accurate diagnosis as the symptoms may be confused with the more serious infection leukoctoclastic vasculitis which is unaffected by antibiotics. Once diagnosed the horse should be kept on clean bedding and turned out in a well-drained field or manege. The infected area should be clipped and cleaned regularly with an antiseptic wash. If the horses’ legs are wet, dry them thoroughly to prevent the skin remaining water logged.
Horse and Hound magazine – 20 December 2012, pages 14-15, Waging war on Mud fever
Figure 1 – horse and hound, chronic pastern dermatitis, May 2010, http://www.horseandhound.co.uk/forums/showthread.php?t=400764