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Consider targeted parasite control in beef and sheep throughout grazing season


Keeping 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.


Weaned beef cattle in their first full grazing season may be at high risk of parasitic gastroenteritis (PGE) and resulting production losses depending on previous parasite management.  Animals that received strategic worming treatments earlier in the season will have minimal worm burdens and be at less risk of parasitic disease as pasture contamination will be low. Those that have not received any worm treatments post-turnout may be carrying significant worm burdens by mid to late summer which may reduce growth rates and can result in costly outbreaks of PGE.

Suckled calves will be eating more grass by late-summer and autumn and with this comes an increased risk of PGE, particularly if dams have been shedding eggs onto the pasture since turnout. Calves should be monitored and a worm treatment at grass considered, especially if growth rates are poor or scouring is observed.

Sioned Timothy says: "Bought-in store cattle with an unknown treatment history could be carrying significant worm and fluke burdens. Ideally, these animals should be quarantined and treated before joining the herd, to prevent an increase in pasture larvae levels and costly outbreaks of PGE."

Cattle which have been exposed to the infective stage of fluke on pasture since turnout may now be carrying chronic infections of late-immature and mature flukes. Fluke infections in growing cattle can have a significant impact on production, through reduced weight gain and longer finishing times4.

Sioned says: "Where fluke is a known problem on farm, a treatment during the grazing season may be appropriate to reduce the impact on production. There are a range of active ingredients available that only target late-immature and mature flukes, such as nitroxynil (Trodax®). One of these should be chosen ahead of triclabendazole, at this time of year."


From mid-summer onwards there is an increased risk of PGE in lambs which can have a major impact on growth rates. A high gutworm challenge also impacts lamb performance which increases finishing times and the cost of production.

Sioned explains: "Parasite control measures taken earlier in the year, such as worming ewes around lambing, should have reduced the risk of PGE and lessened the impact of pasture larvae challenge on lambs. Pasture management techniques including the use of silage aftermath or other safe grazing measures can further help reduce the challenge to weaned lambs."

However, where safe grazing is not available, lambs may have picked up significant worm burdens since turnout. This may now be at production-limiting levels and these animals will be at high risk of PGE.

A targeted approach to treating lambs is advised. This should take into account early season control measures and treatments and an assessment of the risk in individual groups of lambs. Using live weight gains, pooled faecal egg counts (FECs) and post-drench checks can be useful and allow farmers to take an informed approach to treatments.

Rams should not be forgotten in the flock health plan. Keeping breeding animals in good condition before tupping is important, and they can be at particular risk of PGE. Consider the risk that worms pose and treat accordingly.

"The resistance to sheep wormers is increasing," warns Sioned. "It's therefore really important to understand the different properties of the wormer groups and choose the correct treatment to achieve the best control.

"A Group 3 drench such as Oramec®, which contains ivermectin, can be used to control and treat a wide range of clinically important gut worms of sheep. It has a six day meat withhold period and can be used in both lambs and adult sheep. Farmers should speak to their vet or animal health advisor to get advice on choosing the most appropriate treatment.

As with beef and dairy herds, bought-in sheep can pose a risk to the flock, as they could be carrying heavy worm burdens and resistant worms. Sheep farmers are advised to work with their vet or animal health advisor to develop an effective quarantine programme.

As the year progresses, sheep of all ages are at risk from liver fluke infection. The scale of the risk will depend on the climate, such as rainfall and temperature, and the individual farm and flock history.

Sheep are prone to suffering from acute fluke disease during the autumn, when they have picked up large numbers of the infective stage of the parasite from the pasture. The immature fluke migrate through the liver, causing damage and anaemia. Acute fluke causes the most serious disease in sheep leading to significant production losses and even death in some cases.

Treatments that target the immature stages of fluke should be considered if there is a risk of acute fluke in the flock.

Sioned says: "Treating for fluke should also be considered as part of any quarantine strategy for bought-in animals, particularly as the incidence of triclabendazole-resistant fluke is increasing. The choice of treatment for quarantined animals should be discussed with your vet and animal health advisor."

Farm case study - Sheep and beef

Sarah Hull and Cennydd Eynon from Blaendyffryn Farm in Ceredigion, Wales, have 180 head of cattle (store cattle, a small herd of pedigree Simmentals and a small number of commercial Belgian Blue cross suckler cows) and a flock of 160 ewes and lambs. The couple has recently had to change the farm's parasite management programme, mainly due to an increase in sheep numbers.

She explains: "Traditionally the farm had low numbers of sheep and lots of clean grazing, but due to an increase in the flock size we now have to graze contaminated pastures. This has led to us taking a more 'hands-on' approach to our worming and treating where we previously wouldn't have had to."

The ewes in Sarah's flock are given a long-acting wormer to see them through the rise in worm numbers on pasture post-turnout. Meanwhile the lambs are treated with a white drench at approximately four months old. Lambs which remain on the farm are followed-up with a clear or yellow drench later in the grazing season.

A pre-tupping dose for fluke is given to all ewes and rams. Sarah avoids giving fluke doses during the grazing season as there isn't a significant fluke problem on the farm.

Throughout the year the farm will purchase a number of store cattle, which Sarah describes as the biggest risk to parasite infection on the farm.

Sarah says: "We treat each animal upon arrival and then isolate them for 48 hours before they are turned out to grass. They receive a broad spectrum product that covers them for gutworm, fluke and any external parasites."

The store cattle are treated for gutworm at turnout and again eight weeks later, and treated for fluke at housing. Depending on the season, they will either use a flukicide that targets late-immature and adult flukes at housing, and repeat the dose seven weeks later, or they will wait three weeks after housing and use a product that treats all stages of fluke.

The suckler cows receive a fluke treatment at housing, and Sarah hopes that they have built up enough immunity over the year to not require a treatment for gutworm. Their calves receive a pour-on ivermectin solution at housing, unless it's been a particularly wet summer with variable temperatures, in which case they might bring it forward a little.

Sarah believes that their current worming strategy is working effectively but is always mindful of the risk of parasitic disease. She says: "We hope that the strategy we are currently using means that we have as healthy and productive animals as possible, but it's always important to reassess any worming strategy with the aim of improving it in the future.

"Next year we hope to start FECs and faecal egg reduction counting to assess for resistance, and in the longer-term future we hope to be able to base our worming strategies on liveweight gain."

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

Oramec 386 x 81 Trodax

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