Chris Gregory BVSc MRCVS
Winter housing offers the ideal break point in the fluke life cycle; a window of opportunity to clear infestations accumulated in the previous grazing season. The benefits of treatment mainly relate to the improved health of the liver with increased feed conversion, reduced days to finishing and the knock-on effect on other production outputs (e.g. fertility and animal health).
In a series of three articles we will address:
- How to assess the risk of fluke on your farm
- Treatment options/timing
- Follow up sampling/treatments and other key treatment scenarios
(1) How to assess the risk of fluke on your farm
Do I need to treat?
In order to prevent, it’s important to assess the risk of infestation.
- Identify high risk pastures – Fluke needs a mud snail intermediate host and pooled water; essentially any pasture that is prone to saturation, or even temporary pooled water e.g. poached ground.
- Abattoir feedback – Retrospective, but invaluable information. Condemned livers cost the UK industry £3.2 million in 2010.
- NADIS monthly parasite forecasts – Average rainfall and temperature by region of the UK. Trends show that classical fluke seasonality has become less predictable with the advent of a wetter warmer climate. Average rainfall and temperature can give a good approximation of mud snail habitat, generating a real-time, region specific, pasture risk.
- Vet investigations – mainly used as diagnostics for groups of animals. If deployed effectively the tests can be used to assess the timing of fluke exposure as well as just diagnosing animals affected. They also offer the best means of testing the success of treatment, especially if resistance is suspected.
- Faecal sampling (eggs/coproantigen) – Egg counts will only detect established adults, >14weeks into the cycle. Coproantigen will detect 2-3 weeks earlier. Both tests can produce false negative results if used in isolation.
- Blood antibodies – Use sentinel groups of naïve youngstock to monitor when exposure occurs. Antibodies will be seen within 2-4 weeks post exposure to fluke but give no information on level of burden.
Considerations on when to treat?
Apart from just choosing a product there are a whole host of considerations around where and when to treat at housing:
- Age of fluke at housing – Depending on the seasonality of fluke risk cattle entering housing could be carrying fluke at different stages of development; from early immature through to adults. This is the key point when considering the correct treatment. We will cover specific treatment choice in the next article but bear in mind different flukicides target different stages of fluke development. In order to maximise treatment efficacy, it is important to have a strategy.
- Number of handling events and impact of the cattle – Research has shown that excessive handling events have a negative impact on growth rates. In particular, the process of housing and weaning can result in dramatic growth checks. Electing to treat at housing rather than a few weeks later can thus have its advantages. We’ll discuss this further in the next article.
- Type of stock treated – Where rapidly growing cattle are concerned; the impact of repeated handling may be undesirable. However, in less intensively housed animals (e.g. suckler cows) it would be less of an issue.
- Other timed treatments – In many cases combined treatments will be desirable to reduce the number of handling events e.g. wormer. In this case it is important to choose the correct flukicide to complement the timing of the wormer
- Meat withdrawal – All treatments vary and may influence choice of product/timing.
In conclusion; assessing fluke risk and treatment timing around housing will be an ever-changing dynamic based on climate, pasture factors and housing routine. Taking in to account the points above, a well-informed strategy at this stage of the year could well save unnecessary treatment(s), or equally justify the most efficient choice and timing of treatment(s) in the coming months.