High levels of parasitic disease in young cattle and productivity losses in adult dairy cows are a serious risk during the coming grazing season as infective gutworm on the pasture pose an immediate challenge at turnout, warns Merial Animal Health’s veterinary advisor, Sioned Timothy.

The level of infective worm larvae that persists on pasture over the winter period, and the scale of the challenge cattle face at turnout may be greater following the relatively mild winter across much of the UK. These overwintered larvae can quickly infect cattle at turnout, and by mid-summer susceptible youngstock will have established significant infections and be shedding high numbers of eggs. This rapid increase in pasture contamination can cause heavy worm burdens in untreated animals, with resulting losses in productivity and performance, and the risk of outbreaks of disease.

Ms Timothy said; “Calves in their first grazing season are most at risk of disease, and heavy worm burdens will cause ill-thrift and potentially severe scouring. Not only that, we know that gutworm has a potential impact on future performance, particularly fertility. Sub-clinical growth checks mean heifers take longer to reach target weight for first service, and can take longer to get in calf, with multiple inseminations often required1.”

Youngstock in their second season at grass may also be at risk from disease, depending on the level of immunity they acquired in the previous season, and even immune adult cows should be considered in a farm’s parasite control plan

“Despite popular misconception, adult cows will become infected by gutworm,” says Ms Timothy, “Though they carry lower worm burdens, shed fewer eggs and don’t show outward signs of disease, the effect on productivity is well documented; milk production decreases by at least one litre per day in affected animals and the additional potential for reduced fertility with increased calving to conception ratios adds to the overall performance impact.”

The negative effects of gutworm can be avoided through a combination of pasture management and strategic or targeted worm treatments. Farmers should discuss the options with their vet or SQP (Suitably Qualified Person) at their animal health supplier to identify the best approach based on the farm’s individual requirements.

“Planning which approach to take ahead of turnout means that there is less to worry about once the grass starts growing,” said Ms Timothy.

In youngstock, a strategic worming plan, including timed treatments of a suitable wormer such as IVOMEC Classic® (ivermectin) at three, eight and 13 weeks after turnout can help to prevent parasitic disease. Taking this approach early in the grazing season will prevent the amplification of parasite populations in affected animals ensuring pasture contamination remains low throughout the season.

“This approach will only be fully successful if animals are set stocked or moved onto lower-risk pasture, such as silage aftermath, later in the season, and the risk should be reassessed if new cattle are introduced to the group,” stressed Ms Timothy.

Alternatively a targeted approach, where animals are treated following as assessment of the individual or group disease risk, could be adopted. Here, information such as the growth rates of cattle is monitored and used in conjunction with diagnostics, such as faecal egg counts, to determine whether wormer treatments are required.

The targeted approach has the potential advantages of reducing the risk of selecting for wormer resistance by only treating those animals that need dosing, and potentially reducing cost. But, it does require forward planning, attention to record keeping, and additional stock management time.

For dairy cows, the bulk milk Ostertagia ostertagi test (MOO test) is a useful diagnostic tool that assesses the level of gutworm antibody within a sample and provides an indication of the herd-level gutworm exposure (high, medium, low), and the likely impact of this challenge on the herd’s milk production. The results can provide a basis for adopting a more targeted approach to gutworm control in milking cows.

Using a zero-milk withhold eprinomectin wormer, such as Eprinex® , in lactating cattle provides effective gutworm control at any stage of production, without the loss of milk sales.

Using the correct equipment, properly calibrated, will ensure that dosing is accurate and effective. Cleaning and servicing existing applicators and dosing guns now, or purchasing replacements, will save time later in the season.

The new Breaze™ applicator from Merial is designed specifically for Eprinex® , and can dispense up to the full 80ml maximum dose for a 800kg cow in one go, without the need to refill the gun.