Parasite Control in Dairy Beef Calves

By Nollaig O'Dowd

Flying trade for weanlings along the mart ringside has made it difficult for some farmers to secure stock. Many have turned to purchasing the somewhat less expensive dairy-bred stock rather than the continental-bred suckler weanlings they would ordinarily have purchased.

Parasite management of these dairy-bred calves is slightly different compared to suckler weanlings due to the high proportion of grass in their diet from a young age, making them more susceptible to parasite burdens.

Parasites have a significant impact on animal performance, particularly stomach and lung worm during the first grazing season. Older animals are less susceptible as they develop immunity over time.

Stomach Worm

Dairy/dairy beef calves are exposed to stomach or gut worms as soon as they are turned out to grass. Diarrhoea, poor appetite, weight loss or ill thrift are often indications of a stomach worm burden. It is important to treat promptly to reduce the amount of damage done to the animal’s stomach and small intestine, as this may have lifelong effects on animal performance.

Faecal egg counts (dung sampling) can confirm or rule out suspected cases of stomach worm infestation, and this is a service offered by most veterinary practices nowadays. Getting dung sampled prior to treatment is important as it will confirm if treatment is required and ensure you are targeting the correct parasite. It plays a major role in preventing anthelmintic resistance – an issue that many farmers are experiencing. All in all, it saves time, money and has a positive impact on animal performance. Contact your vet to arrange a faecal egg count test.

Lung Worm

Coughing or difficulty breathing are often the first indicators that there may be a lungworm burden. The highest number of cases is often seen in late summer or early autumn following high levels of rainfall. Animals affected by lungworm, otherwise known as ‘hoose’, are often more susceptible to both viral and bacterial pneumonia. Dung samples are not ideal for detecting a lungworm burden, especially at the early stages, as only adult lungworm will shed larvae – therefore, close monitoring of livestock’s breathing and coughing is important. Calves should be treated at the first signs of coughing.

There is no proven resistance of lungworm to anthelmintics, so it is an ideal opportunity to alternate between the drug classes: white, clear and yellow. Benzimidazoles (white) and levamisole (yellow) should kill the ‘hoose’ present on the day of administration but have no persistent activity, meaning they will not kill lungworm picked up after dosing. Macrocyclic lactones (clear) have 4–17 days’ persistency. Consult your vet with regard to treatment and control of lungworm.

Summer Scour Syndrome

Summer scour syndrome is a condition which can easily be mistaken for parasite infections such as coccidiosis, mineral toxicity, acidosis or BVD. Symptoms of summer scour include scour, rapid weight loss, lethargy, weakness and death. Some calves also develop oral and oesophageal ulcers. An exact cause has not yet been identified, but it is thought that the calf’s rumen development plays a part. The condition is often seen in calves grazing lush pastures with high protein and low fibre content. With calves also being selective grazers, they tend to consume the top of the grass plant, which has a high nitrate content – leading to excessive ammonia in the rumen.

A few measures can be put in place to help rumen development and minimise the risk of the condition. Calves should be introduced to meal from one week old to help with rumen development, and should not be weaned off milk until they are consuming at least 1 kg of concentrates per day. Turn out calves to stemmy or older pasture rather than lush swards. Add an extra source of fibre such as hay or straw if required. Avoid reseeds or pasture that has received high levels of slurry or nitrogen for the first two months post-turnout. If you have suspected cases of summer scour syndrome, remove calves from the pasture immediately, house them, and discuss treatment with your vet.

Parasite Control Plan

To conclude, having an animal parasite control plan, regular faecal egg sampling, and close monitoring of livestock will ensure optimal animal performance.