This year’s wet weather has thrown worm control plans into confusion, making monitoring stock even more crucial. We spoke to a vet to find out why and what producers should do.
TEXT REBECCA DAWSON
Delayed turnout and the wet spring and early summer may have changed expected patterns of worm infection this season. According to Boehringer Ingelheim Animal Health’s Sioned Timothy this could make traditional, timed and blanket-treatment approaches to worm control less effective. “Monitoring cattle for worm infection and signs of disease, and adopting a targeted approach, is a much more effective way to manage parasites, particularly this year,” she says.
“Delayed turnout may have reduced some worm infection by allowing overwintered worm larvae to die off, but the disruption caused by cattle being on different pastures to those planned, has caused problems in other areas.”
Where sheep co-graze pastures, they may have eaten grass ear-marked for cattle early in the spring. This may have changed the paddocks available to youngstock and necessitate use of grazing that would otherwise have been left for a longer period before use.
Increased risk
“With most worm larvae found in the bottom of the sward, grazing shorter grass poses an increased risk of worm infection,” adds Ms Timothy. “So cattle should be moved on before paddocks are eaten down to an extreme.” Where fields are rotationally grazed, some paddocks are coming back into the rotation later than planned, which can slow down the ability to move cattle. First-cut-silage delays have also had a knock-on effect in terms of when aftermath is available for grazing.
“Aftermath is an important source of clean grazing, suitable to move youngstock onto later in the summer. Delays of a couple of weeks or so will mean that animals most at-risk of parasitic disease may have to stay on increasingly infected pastures for longer. “This will likely have an impact on how worms are managed later in the season,” explains Ms Timothy.
Gutworm infection on pasture usually peaks around mid-summer, but late turnout means this could be different this year. The wet spring has also provided ideal conditions for larvae survival, so where youngstock were turned out onto contaminated pasture, infection rates could have increased rapidly.
“The problem is that it’s all quite unknown and will vary from farm to farm, depending on individual circumstances,” says Ms Timothy.
The only way to really understand how the worm dynamics are changing on individual farms is to monitor it. Faecal egg count (FEC) tests are a useful tool to monitor the level of worm egg output in the first half of the season.
Close monitoring: check grazing heifers' growth rates and watch for signs of coughing
Gutworm burden
“From turnout, performing pooled FEC tests on a group of between 10 and 12 animals from each youngstock group, every four weeks, can help producers to understand how quickly worm infections are increasing, and allow them to judge when to move cattle to cleaner grazing, and/or use a wormer treatment to reduce the infection.”
She urges producers to ask their vet, or local farm store SQP, about adding FEC monitoring to herd health plans. Vet practices are increasingly offering FEC testing as part of their services, with some having their own in-house labs to analyse the tests. Others will provide the test kit for producers to send away to a lab, and the herd vet can then talk through the results when they come back.
Ms Timothy also suggests growth rate monitoring as another option to manage gutworm burdens and identify whether individual animals need treating.
“Weighing youngstock regularly throughout the season can help identify any individuals that are not making their average daily-liveweight-gain targets.
“If targets are being missed, but there has been access to adequate nutrition and no other health issues, then it’s most likely that a gutworm burden is the cause of slow growth. In these circumstances, it’s prudent to treat just those poorly performing individuals, and leave a proportion of well-performing ones untreated. “Not only is this approach more cost-effective, without reducing overall herd performance, it’s also more sustainable,” says Ms Timothy.
“By leaving some animals untreated producers leave some gutworms ‘in refugia’, meaning they are not exposed to the wormer. Well-performing animals can carry a small burden of worms without it impacting their performance, which in turn ensures some worm eggs are passed out onto the pasture.
“This targeted approach results in a more diverse pool of worm genetics in the environment compared to a blanket-treatment approach, and reduces the risk of wormer resistance developing,” explains Ms Timothy. Taking a targeted approach to wormer treatment decisions, either with weight-tracking or FEC monitoring, means the use of long-acting wormers from turnout may not be the best approach.
A shorter-acting but effective wormer treatment, such as IVOMEC Classic or EPRINEX Pour-On, allows for light re-infection of gutworm species 21 or 28 days later (respectively), which reduces the risk of resistance, while still protecting productivity.
Lungworm requires a different approach to gutworm. Keeping a close watch for signs of coughing remains the most effective way to identify infection in cattle, and catching it early is key. Most lungworm infections start with a small number of infected animals. It can take time for all the herd to be coughing, at which point it’s an extremely serious infection.
“Youngstock have traditionally been the most at-risk group for lungworm but, increasingly, adult cows are being infected too, so it pays to remain vigilant,” warns Ms Timothy.
Regular monitoring
“Where youngstock are grazed away from the main holding, they need regular monitoring. A harsh cough, at rest or when walking, is an indicator that something isn’t right. Lungworm can be challenging because it’s highly affected by the weather,” adds Ms Timothy.
“It thrives in warm, wet conditions, but periods of hot and dry weather mean larvae get locked-up in dung pats. This can then result in a mass eruption of larvae during heavy rainstorms, making pastures highly infective.”
Lungworm vaccines given before turnout are a good option for farms with a known lungworm problem, but under high worm challenge this immunity can be overcome. Any animals that have not built sufficient immunity to lungworm in their early years, and consistently received limited exposure year on year, are also at risk when faced with a high lungworm challenge.
“Where treatment is required, the whole group must be wormed because even though symptoms may develop over time, all animals in the group are likely to be infected,” explains Ms Timothy. “Early treatment will support better outcomes, which is why vigilance is important.”
A zero-milk withhold wormer, such as EPRINEX Pour-On (eprinomectin), is suitable for use in both youngstock and adult cows, and prevents re-infection from lungworm for up to 28 days. “Depending on the severity and progression of disease symptoms, supportive treatments to manage pain and secondary infections may also be prescribed by the herd vet,” she adds.
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