Mid-Season parasite control

Enda Maloney, Teagasc Westport

An important factor to achieving the desired level of animal performance on calf-to-beef systems during the grazing season is ensuing they are free from parasites. Parasites can have a substantial impact on animal performance therefore it is imperative that stock are free from burdens to prevent any impact on thrive. After the dry spell of weather in June followed by a very wet July burdens have started to develop therefore it is important to monitor and treat these to prevent any reduction in performance.

Worms are a particular issue in dairy calf to beef systems due to the fact the majority of the animals on the farm have very little immunity to worms due to their age profile with stomach and lung worms been the main parasites

Calves are particularly vulnerable to infection from stomach worms and this can result in ill-thrift and reduced growth rate. The target average daily gain for a dairy calf to beef calf for its first season at grass is 0.8 kg/day. After their first grazing season cattle generally develop sufficient immunity to prevent clinical disease, however there has being numerous cases where older animals have had high levels of worm burden therefore regular monitoring is required in older groups to ensure no issue arises. Symptoms of stomach worms can include diarrhoea, decreased appetite and loss of weight. Stomach worms can cause severe damage to the stomach and small intestine which will cause parasitic gastroenteritis therefore monitoring is essential to prevent such issues from arising.

Regular dung sampling to assess faecal egg counts (FEC) is an excellent way of way of identifying a worm burden in a group. Where readings in excess 200epg are recorded treatment is advisable.

Control of stomach worms on dairy calf to beef farms is usually achieved by the administration of anthelmintic doses. There are currently three classes of anthelmintic licensed for the control of stomach worms in cattle benzimidazole (white) levamisole (yellow) and, macrocyclic lactone (Clear). These products have been highly effective in controlling stomach worm infection in cattle however in recent studies carried out by Teagasc showed resistance to all three classes of product.

When implementing a dosing strategy it is good practice to alternate between the different classes of drug to minimise the risk of a potential resistance build up on farm. Taking a dung sampling a few weeks after treatment is good practice to ensure the product used gave an effective treatment.

In the case of lung worm monitoring for clinical signs such as a husky cough or difficult breathing is the best way to identify if there is an issue. Heavy infestations can lead to respiratory disease therefore rapid treatment is advised. As regards treatment and control most available anthelminthic are effective against larval and adult lungworms. Levamisole and white drenches will take out what parasites are there on the day of treatment and but will have no residual affect as a result shorter treatment intervals will be required whereas macrocyclic Lactones such as Ivermectins will give longer protection.

Best practice when dosing

Farmers should dose based on the weight of the heaviest animal in the bunch and where a large degree of weight variation exists, splitting the group into a heavier and lighter group and then dosing based on the heaviest in each group is advisable. When choosing a product it is important to read the label and instructions carefully to ensure that you know exactly what the dose can and cannot treat. Post treatment it is best to dose and return to dirty pasture for a few a couple of days as this will help to reduce anthelmintic resistance.