Mid-season worm pressures affect dairy herds

Managing mid-season worm pressures could have significant economic and performance benefits for dairy herds. This is the advice from the COWS industry steering group (Control of Worms Sustainably) this summer.

Anthelmintic resistance is a growing concern in the dairy industry. As the peak parasite season approaches, careful monitoring of dairy heifer condition is essential.

The financial benefits of replacement heifers calving down at 24 months is well-known. Dr Andy Forbes, COWS technical representative and Honorary Professor at the University of Glasgow’s School of Veterinary Medicine, explains that for each week the 24 month target is missed, the average cost to the business can be up to £1,171 per 100 head of cattle.

In order to achieve the 24 month target, replacement heifers need to be at 65% of their mature bodyweight by the time they’re 15 months old.

“Holstein and Friesian heifers should average a DLWG between 0.7 and 0.8kg per day. When this falls below the set target, or a loss of body condition associated with ill thrift is seen, this may indicate the need to implement worm control measures.

“Sub-clinical and clinical cases of worms are one of the most common reasons why replacement dairy heifers fall behind growth targets.”

Dr Forbes advises that a range of measures are taken to keep potential worm burdens in check. “Using faecal egg-counts is an effective way of monitoring pasture contamination, and it has been shown that sampling about eight weeks after turnout, in mid-season grazing, can help predict the risk of potential worm challenges later on.

“When the egg count is greater than 200, it’s likely that cattle are at risk of clinical disease and production losses.”

He adds, “It’s important that cattle receive the correct dose of cattle wormer. Both under-dosing and over-dosing can have significant implications. Over-dosing is costly, and avoidable; under-dosing can lead to poor efficacy and an increased risk of resistance.”

To ensure an accurate dose of anthelmintic is given, Dr Forbes recommends weighing each animal, or using a weigh band. “Judging cattle weights by eye can be very inaccurate and can lead to the adverse effects of under- or over-dosing cattle.” He also advises that dosing equipment is calibrated and regularly checked for accuracy.

“By following COWS best practice guidelines, and working with your vet or farm adviser to reduce the risk of worm burdens, the productivity of the herd can be maximised,” he says.

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