Summer dosing strategies for dairy beef animals
An important factor in achieving the desired levels of animal performance on calf-to-beef systems during the grazing season is ensuing they are free from parasites. Due to its grass-based nature, dairy beef animals are particularly exposed to outbreaks of stomach worms and lungworm.
Parasites can have a significant impact on animal performance. It is therefore imperative that burdens are monitored to prevent any reduction in performance.
Stomach worms
Calves are particularly vulnerable to infection from stomach worms and this can result in ill-thrift, with subclinical infection resulting in reduced growth rate. After their first grazing season, cattle generally develop sufficient immunity to prevent clinical disease. However, there have been numerous cases where older animals have had high levels of worm burden.
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. Cattle in Ireland are usually infected with a number of stomach worm species, the most common being Ostertagia ostertagi and Cooperia oncophora.
The level of worm burden in a herd can be ascertained by counting the number of worm eggs per gram (epg) of faeces (faecal egg count or FEC). Most veterinary practices offer a faecal testing service to help determine if dosing for worms is required. In order to avoid worm resistance building up on farms, farmers should take dung samples to see if a worm dose is warranted or not. Where readings in excess 200epg are recorded, treatment is advisable.
Control of stomach worms
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, 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 sample a few weeks after treatment is good practice to ensure the product used gave an effective treatment.
Lungworm
In the case of lungworm, 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 or pneumonia. As regards treatment and control, most available anthelmintics are effective against larval and adult lungworms.
Levamisole and white drenches will take out what parasites are there on the day of treatment, but will have no residual affect and as a result shorter treatment intervals will be required. Macrocyclic Lactones such as ivermectins, on the other hand, will give longer protection.
Best practice when dosing
When administering a drench to stock, particular attention needs to payed to dose-to-weight calculations, so animals receive a full dose. Farmers should dose based on the weight of the heaviest animal in the bunch. 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. It is best to dose and return to dirty pasture post treatment, as this will help to reduce anthelmintic resistance.
Peter Byrne’s parasite control plan
Peter Byrne is a participant in the Teagasc DairyBeef 500 Campaign. Traditionally, on the farm, calves would have been treated for worms with an ivermectin-based product three weeks after turnout and then every five weeks after this - whether they were showing signs of a worm burden or not.
However, since joining the Teagasc DairyBeef 500 Campaign, Peter has changed his dosing strategy. From the end of May, Peter starts taking regular faecal egg samples to check the levels of stomach worm burden in all groups of stock. The results of these tests will determine when a dose is administered.
“Last year, I didn’t dose the calves until the first week in June and the yearling cattle wouldn’t have received their first dose until July. Generally I won’t go in with a dose until the FEC goes above 200epg,” Peter explained.
Performance of the calves remained good last year, with average daily gain (ADG) for these animals through the summer being 0.8kg. With regards to lungworm, when the first signs of coughing start to appear, Peter would administer a treatment. When treating, tries to alternate between the different classes of drug used to try and prevent any resistance building up on the farm.
This article first appeared in the DairyBeef 500 booklet produced as part of a recent farm walk on Peter Byrne’s farm. More information on the DairyBeef 500 Campaign is available here.