Flies are notorious for causing a nuisance to cattle but are you aware they can be responsible for more serious issues, such as the transmission of disease between animals?
In the UK there are at least 20 species of fly which feed on cattle. Different species of flies feed on different secretions or tissues. Some pierce the skin and feed on blood; while others feed on secretions such as sweat, skin secretions, saliva, or tears. Some flies even feed on excretions such as urine or faeces.
There are two ways in which flies cause harm to cattle:
Summer mastitis occurs generally in non-lactating animals (cow and heifers) during the summer months. It is a bacterial disease caused by a number of bacteria acting synergistically. It is believed to be spread primarily by the fly Hydrotea irritans.
In cattle, large numbers of this fly cluster on the ventral abdomen and udder and the bacteria is mechanically transmitted from animal to animal.
The fly Hydrotea irritans lives in sheltered areas such as bushes/trees and only has the ability to fly in very calm, damp, humid conditions. As a result of this, the incidence of summer mastitis is highly variable and tends to be associated with ‘problem fields’ e.g. adjacent to woodland.
Disease may be present for up to a week before the animals appears systemically ill which is why it is important to check stock frequently during high risk periods. Be observant and look for swollen/enlarged teats - the consequences of summer mastitis are severe and animals may abort/die if untreated.
Infection Bovine Keratoconjunctivitis
This disease often goes by ‘New Forest Eye’ or ‘Pink eye’. It is a highly infectious disease caused by the bacteria Moraxella bovis. It can spread rapidly during the summer months and is more common in young stock. Head and nuisance flies act as mechanical vectors for the spread of this disease. The ocular lesions are very painful and disrupt grazing patterns resulting in poor performance and weight loss.
Blue Tongue and Schmallenberg in cattle
Both of these diseases have been shown to be transmitted by the Culicoides species of fly.
Bluetongue virus is generally not symptomatic in cattle. However, cattle act as reservoirs of infection which can be transmitted to sheep causing more severe disease.
Schmallenberg rarely shows clinical disease in adult animals and often the first suspicion of disease occurs when a deformed calf is born. Where it does affect adult cattle, it causes milk drop, fever and diarrhoea.
Your local vets and SQPs have a great deal of fly control knowledge so speak to them for advice and they can help you to design an appropriate strategy for your herd.
About the Author
Rachel Mallet is a Veterinary Surgeon, who now works as a Professional Services Vet providing technical support to vets, SQPs and farmers in the UK. Rachel is passionate about animal health and about promoting best practice and preventative medicine amongst farmers.
Use medicines responsibly. Noah.co.uk/responsible.
*Dectospot contains 10mg/ml deltamethrin and is a POM-VPS medicine.
The following active ingredients have indications for fly control in cattle: Deltamethrin, Alphacypermethrin, permethrin, cypermethrin cis 50: trans 50, moxidectin, doramectin, ivermectin.
Please consult your SQP or vet to determine which is the most appropriate for your herd and consult the SPC data sheets on the VMD website for further information on which species of fly are controlled and with which preparations.
There is a great deal of pressure when trying to finish lambs for sale and there are numerous factors which can result in delays. Trace element status of growing lambs is an aspect which should not be overlooked as deficiencies and toxicities will lead to reduced productivity.
Did you know that an adequate supply of cobalt is critical for lamb growth? After cobalt is consumed by the lamb, it reaches the rumen where bacteria utilise the cobalt to produce Vitamin B12. This Vitamin B12 is integral to glucose synthesis and thus impacts on how the lamb utilises its food (as such the food conversion ratio of that animal.)
Ruminants have no capacity to store cobalt and as a result lambs are very susceptible to Vitamin B12 deficiency. This is also known as “pine” and can result in poor growth rates. In order to tackle a cobalt deficiency a continuous supply of cobalt must be utilised (such as a bolus).
Selenium is required to produce proteins which are integral to the innate and adaptive immune system. Therefore Selenium plays an important role in disease defence. A relationship exists between selenium and iodine and so they must always be considered together when investigating suspected deficiencies.
Iodine is integral to the thyroid hormones T3 and T4. The thyroid hormones regulate the rate of metabolism and control the rate of absorption of carbohydrate from the gastrointestinal tract. This rate is important in achieving a good food conversion ratio. In lambs, for the inactive T4 to be converted into an active T3, an enzyme which contains selenium must be present.
Copper is a component of enzymes which are important for energy metabolism. It is very important to remember that copper can be toxic to sheep and so copper supplements should only be given if a deficiency has been diagnosed. Blue faced Leicester and Texel sheep are particularly susceptible to copper toxicity.
Forage is incredibly variable not only between fields on the same farm, but from year to year. You must also take into account any other supplementation given such as concentrates, lick buckets, drenches etc and you can begin to see that it’s impossible to take a ‘one shoe fits all’ approach between different management systems.
You should work with your vet to determine which, if any, trace element imbalances are present within your livestock. This is very important because there is no benefit to giving trace element supplementation if no deficiencies exist. Indeed, it may even harm the lambs as copper and selenium can be toxic if over supplied.
From a commercial aspect there are two main considerations which justify the importance of investigation:
Sheep, Blue faced Leicesters and Texels in particular, are susceptible to copper toxicity. Selenium may also be toxic if over supplied. Please consult a vet or nutritionist to establish the need prior to supplementation.