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Consider targeted parasite control in dairy cattle throughout grazing season

Merial-Sanofi_Logo_rgbKeeping on top of parasite control in cattle and sheep through the year is vital to prevent losses in production and serious clinical disease, warns Merial Animal Health, in a Season Ahead video for the mid-late grazing period. Watch the video:

"There are a number of parasites that will affect livestock in mid to late summer and into autumn," says Merial's veterinary advisor, Sioned Timothy, host of the video. "It's important to be aware of the risks at individual farm level and take into account the weather, previous animal health treatments and the results of any diagnostic tests."

She continues: "Every farm is different so it's important that each has its own parasite management programme that can identify parasite diseases and then treat any outbreak appropriately. Failure to do this can result in significant production losses which can hit livestock businesses hard."

Most farms will have put in place a parasite management plan before the summer grazing period, to limit the impact of parasites, but farmers are still urged to be vigilant for any signs of parasitic disease.

Dairy - Gutworm

In dairy herds, the most damaging gastro-intestinal parasite is gutworm (Ostertagia ostertagi) which can cause production losses throughout the life of cattle, both in terms of milk yield and fertility parameters1. First season grazing heifers are most at risk of gutworm but second season grazing heifers are also prone to clinical disease.

Annwen Richards, veterinary surgeon at Tysul Vet Group in Carmarthenshire, Wales, explains that there are different approaches to managing parasites in adult dairy cows.

She says, "Blanket treatment of the dairy herd once or twice during the grazing period depending on the level of the gutworm challenge is an option. However, this approach should ideally take account of the farm and herd history, parasite management practices, grazing patterns and the results of diagnostic tests.

"Treating adult dairy cows around the time of calving is another approach. Removing gutworm at this time has been shown to improve dry matter intake, milk yield and fertility2."

Young calves in the first grazing season are most naïve to gutworms, so Annwen advises that they may need treatment following turnout, depending on the status of the pasture.

She explains: "For calves on safe pasture it's important to monitor growth rates and body weight, and use Faecal Egg Counts (FECs) to assess the gutworm challenge. Unfortunately, most farms have little safe pasture available. Therefore when calves are being turned out to dirty pasture, it's important to treat gutworm three weeks post turn-out followed by further treatment later in the grazing season depending on the level of gutworm challenge."

Llion Davies from Glaspant Farm in Ceredigion, Wales, has a herd of 180 dairy cows on a year-round calving system. They also breed their own replacements.

A recent high-positive MOO Test result (bulk milk test for Ostertagia ostertagi antibody) revealed a high gutworm challenge, which has led to a change in management of gutworm within the herd.

Llion says: "To counteract the high-gutworm challenge that showed up in the MOO test we intend on worming the cows as they calve, especially those which are dry and have been out at pasture for a couple of months. We'll worm them a week or so after they calve-down, in small batches, which will hopefully resolve the problem.

"We run quite a strict worming programme for our youngstock. We intend to calve as close as possible to 24 months so they're wormed as they're turned out, at mid-season, and then again at housing."

Dairy - Lungworm

Lungworm poses a risk to cattle from mid-summer onwards and can lead to considerable losses, including impaired milk production, fertility issues and the additional costs of treatment and potential replacements3. A lungworm infection can cause long-term production losses in the herd, especially if youngstock are affected. Lung damage can leave animals susceptible to secondary infections and affect long term productivity.

In recent years, there have been more cases of lungworm reported in adult dairy cows, rather than the youngstock traditionally thought to be most affected. Dairy farmers are advised to be vigilant for any signs of animals coughing at grass, and request a diagnosis from their vet as soon as possible to prevent herd-wide outbreaks.

Annwen says: "The use of long-acting wormers in youngstock means that adult cows may fail to develop sufficient immunity to the disease. This is why it's so important to achieve a balance of exposure to lungworm larvae and effective treatment to allow immunity to develop without causing clinical disease and production losses. Strategic dosing for gutworm in a cow's first grazing season will often treat lungworm.

Annwen continues: "It's important to assess the risk of brought-in replacements as those animals with an unknown history and with potentially no immunity or an existing lungworm infection may contribute to the level of infection on the pasture.

"Farmers must also remain alert to the risk of lungworm later in the season as cases in the autumn are still possible."

Lungworm can be difficult to diagnose at an early stage and may not be spotted until a full-blown outbreak occurs. A veterinary diagnosis should always be sought before treating for lungworm.

If lungworm disease is diagnosed then the whole herd will require treatment. One treatment with EPRINEX® will clear larval and adult stages of lungworm and prevent reinfection for up to 28 days, with zero milk withhold. The weatherproof formulation means animals do not have to be kept in should bad weather occur around the time of treatment.

In severe cases, farmers are advised to consult their vet as supportive treatment may be required to relieve pain, manage inflammation and treat any secondary infections.

The Season Ahead video, by Merial Animal Health is available to view online:


1. Charlier et al (2009) Gastrointestinal nematode infections in adult dairy cattle: Impact on production, diagnosis and control, Vet Parasitol 164: 70-79

2. McPherson  et al. Proceedings of the American Association of Veterinary Parasitologists. 44th Annual Meeting, New Orleans, Louisiana, USA, 1999 Abstr. 28

3. Holzhauer et al. Lungworm outbreaks in adult dairy cows: estimating economic losses and lessons to be learned. Veterinary Record. 2011 169:494.

4. Johnson EG, Agri-practice, 1991

Eprinex formula for success

Merial-Sanofi_Logo_rgb EPRINEX® 0.5% w/v Pour-On for Beef and Dairy Cattle contains eprinomectin. EPRINEX® and the steerhead® logo is a registered trademarks of Merial Ltd. ©Merial Ltd 2016. All rights reserved. Legal category: POM-VPS (UK), LM (Ireland). Advice on the use of these or alternative medicines must be sought from the medicine prescriber. For further information refer to the datasheet, contact Merial Animal Health Ltd CM19 5TG, or call the Merial Customer Support Centre on 0800 592699 (UK), 1850 783 783 (Ireland).

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