We offer important pointers on how to take timely action to protect dairy cattle from parasites, and their associated health and production losses, this winter-housing period.
TEXT REBECCA DAWSON
Take steps to prioritise autumn parasite control in the cattle most likely to experience production loss during the winter. That’s the advice from Boehringer Ingelheim Animal Health’s Sioned Timothy, who says that calves and heifers are the most likely to be impacted by a worm infection during the housing period. Parasite control can play a key role in determining whether an animal will achieve its full potential. Untreated worm or liver fluke infections in calves and heifers will reduce feed intake and average daily liveweight gains, extend growth targets, delay puberty, increase production costs, and reduce lifetime production and profitability.
“It’s inevitable that young animals that were grazed this summer will have picked up some parasites from the pasture,” says Ms Timothy. “The gutworms Ostertagia ostertagi and Cooperia are the most common worm infections and both are endemic to UK farms. Depending on the farm’s history, the weather conditions during the summer, and whether any preventative vaccinations were used, cattle lungworm may also be a threat.
“Given time, and with careful management, cattle can develop immunity to gutworms and lungworm, and this can help prevent clinical disease. But liver fluke is different and cattle remain susceptible to the negative impacts of this parasite on their health and productivity throughout their lifetime,” explains Ms Timothy. Liver fluke isn’t present on all units, so it’s important to understand the history of the pasture grazed, determine whether quarantine procedures have been used in the past with new animals, and regularly review any abattoir reports or other diagnostic tests to determine if this parasite is present or infection levels are increasing. “Testing ahead of housing can determine the fluke status of your herd and whether treatment may be required,” she adds.
Calves and first- and second-season grazing youngstock are most at risk of a parasitic disease called Type 2 Ostertagiosis. This can develop when these animals acquire a high gutworm burden during the grazing season and fail to receive an effective worm treatment around housing time.
“In recent decades this disease has become rare because youngstock have typically been treated during the grazing season,” says Ms Timothy. “But, as we work to reduce our reliance on wormer treatments, there is a chance that animals will reach the housing period with heavier burdens of the dormant, encysted stage of gutworms. If animals are left untreated, mass emergence of these encysted worms from the stomach wall in late winter or early spring can cause severe scouring and potentially death,” she warns.
Targeted treatment: housed youngstock may be at risk from parasites picked up during grazing
“Even if not fatal, there will be a significant growth check and reduced production potential in that animal, as well as increased costs from responding to the disease outbreak,” she says.
Ms Timothy says the best defence against winter scours is to risk-assess the likely worm challenge that youngstock have faced at grass, and treat them using a quality wormer that’s effective against gutworms, including the encysted stages of Ostertagia ostertagi.
“The herd’s vet or local SQP is well-placed to help producers assess the likely threat, and by reviewing the parasite management methods used during the year, including grazing usage and rotation, in-season wormer treatments, and the age and likely immune-status of groups of animals, they can advise on the best treatment option for individual circumstances.”
The impact of parasites goes beyond winter scouring. In heifers, the post-calving energy gap, or negative energy balance, can be exacerbated by a parasite burden. Producers should be aware that a gutworm challenge at this critical time can lead to reduced milk production and impaired fertility, with increased calving-toconception times and an overall reduction in yield in a heifer’s most productive period. “Any heifers due to calve during the winter months should be prioritised for a worm treatment at housing,” says Ms Timothy.
“Not only will this remove the additional impact of a parasite burden on energy needs at calving, but also these animals will be able to make full use of winter rations, putting them in a better position at calving to maximise milk production in early lactation.
“If treatment needs to take place close to calving there are zero-milk-withhold wormers containing eprinomectin, such as EPRINEX Pour On, that eliminate lost milk sales from treated animals.
“Where milk withhold isn’t a concern – in younger cattle, bulls, or cattle reared for beef – products containing ivermectin, such as IVOMEC Classic Pour On, are also effective against the major cattle worm species, including the encysted stage of Ostertagia ostertagi, and external parasites.
“Choosing a liver-fluke treatment for dairy cattle at housing is complicated by long milk-withhold times in lactating dairy cows and heifers. Again, the herd vet or SQP can advise on the best treatment protocol for each situation,” she says.
“There are more flukicide options for calves and youngstock, and in situations where young animals need to be treated for both gastrointestinal worms and liver fluke, combination products such as IVOMEC Super, containing ivermectin and clorsulon, can offer a practical treatment choice where appropriate.”