21 Aug 2018
Test before autumn worm control
Recent polls highlight knowledge gaps around worm monitoring strategies which threaten the sustainable use of anthelmintics.
Grazing cattle, particularly first or second grazing season youngstock, are likely to be at risk from worms on pasture in mid to late summer.
This is in part driven by the usual ‘mid-summer rise’ in pasture contamination, which may have been exacerbated by the climatic conditions this season.
A dry start to the year suppressed early parasite infectivity on pasture, but recent warm wet weather has provided ideal conditions for worms to infect grazing animals.
Boehringer Ingelheim’s technical manager Sioned Timothy is advising cattle producers to monitor signs of a worm burden in grazing animals through summer and into autumn.
She says: “With parasite infectivity on pastures likely to rise in the latter part of summer, we suggest producers assess the potential worm burden in cattle to allow appropriate treatment decisions to be made to control them at housing.
“It is important to make treatment decisions which protect livestock productivity and also safeguard the long-term effectiveness of anthelmintics.”
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“It is disappointing to see the message around responsible and sustainable use of anthelmintics is still not getting through."
Sioned Timothy
Knowledge gap
“Understanding key factors which can influence the risk of infection during the grazing season is an important part of effective monitoring.
“With this in mind, we recently conducted a number of polls through Farmers Guardian’s Facebook, Twitter and Instagram channels to determine awareness of some of these risk factors.
“The results have shown a concerning number of respondents are unaware of the approaches they could be taking to monitor and reduce parasite burdens in grazing cattle.” When asked whether it was true or false that reducing stocking density reduces parasite risk, most respondents to the poll chose the incorrect answer.
Only 104 out of 229 (45 per cent) replied correctly ‘true’.
When it came to understanding anthelmintic resistance, poll respondents were also lacking in knowledge.
Questions around best practice for resistance management, such as leaving some cattle unwormed and not adopting a ‘dose and move’ strategy, were asked twice each in different ways to test understanding.
In all cases most respondents selected the incorrect answer.
Sioned says: “It is disappointing to see the message around responsible and sustainable use of anthelmintics is still not getting through.
“For several years we have been advising cattle producers to adopt a more targeted approach to worm control, using various assessment techniques, and to avoid blanket-treating the herd.
“We have also been strongly advocating against using ‘dose and move’ strategies which are highly selective for resistant worms.
“The lessons of the sheep industry have not been learned by cattle producers yet, but anthelmintic resistance is a real threat.
“If we don’t implement some simple safeguards now, we could jeopardise the effectiveness of parasite control in the long-term.”
Identify the threat
Cattle are often infected by several parasite species at the same time.
So understanding which species you have on-farm and their lifecycle will help identify the right testing and monitoring strategies and the most appropriate treatment.
The most common worms affecting grazing cattle are the gutworm species Ostertagia ostertagi and Cooperia oncophora and the lungworm Dictyocaulus viviparus.
A parasite control strategy should also take the threat posed by liver fluke (Fasciola hepatica) into account.
Without investigation and some diagnostic tests, it is not possible to tell which species are infecting the herd.
Grazing cattle can be assessed for worm burdens in a number of ways.
A simple method of identifying a potential gutworm burden is to weigh growing animals and benchmark them against target daily liveweight gain.
Ideally, animals should be weighed throughout the season, but an autumn stock check before housing is also a good time.
Calves and youngstock in their first and second grazing season which are receiving sufficient nutrition, but are not meeting growth targets, are likely to be facing a high gutworm challenge.
Selectively treating individual animals which are behind target removes the worm burden and its negative effect on production, while avoiding the high selection pressure for anthelmintic resistance associated with whole group treatments.
This strategy can also potentially reduce treatment costs.
TREATMENT TIPS
- Once individual animals and groups of cattle have been identified as requiring anthelmintic treatment, it is important to select the most appropriate product
- Choose a product which targets the parasites/ stages being treated. Combination products containing a wormer and flukicide may be the most appropriate option at housing if treating gutworms and liver fluke, and can save time and additional handling Correct administration is also important.
- Weigh cattle before treatment and select the correct dose rate by individual animal weight, according to label recommendations Use an appropriate applicator and calibrate it before use. Do not forget to keep accurate records of dates, dosage and product, and observe milk and meat withdrawal times
Reducing selection
If weighing is not possible, another approach to reducing selection for resistance when treating animals at grass for gutworm is to leave 10-20 per cent of the best performing individuals in the group untreated.
Faecal egg counts (FECs), widely used in the sheep sector as a decision-making tool, are a less reliable measure of worm burden in cattle because they develop immunity to gutworm.
However, sampling of first season grazing cattle six to eight weeks after turnout can give an indication of the pasture challenge the group has faced and help inform treatment decisions later in the grazing season.
FECs should also be performed to check treatment effectiveness on a regular basis.
Treatments targeting gutworms may also help to control lungworm, however it is important to stay vigilant for the early signs of lungworm in cattle of all ages throughout the grazing season.
These include coughing at rest and when moving, less time spent grazing, milk drop and weight loss.
It is important to ask your vet for advice as soon as possible after observing possible symptoms, as lungworm needs to be treated quickly.
In adult dairy cattle, bulk milk samples can be tested for the presence of antibodies to certain parasites including Ostertagia ostertagi and Fasciola hepatica.
These give an indication of the level of exposure to those parasite the milking herd has faced.
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