Employing a season-long worm and fly control strategy may not only provide protection, but also result in less labour and reduced animal stress.
British Dairying reports.
Gut and lung worms can hamper productivity on dairy farms, affecting youngstock weight gain, carcass quality and milk production. The annual cost of worms through lost production and treatment has been estimated at £149m for the UK dairy industry. Fly worry can also be costly, with growth rate losses in youngstock of up to 0.3kg/day and milk losses of up to 0.5 litres/day.
Andrew Venables at Hills Green Farm, near Macclesfield, Cheshire, follows a season-long worm and fly control strategy, helping him avoid the stress of repeated handling of first and second grazing season heifers.
“We had a lot of ups and downs with the previous worm control.”
He runs 240 Holstein Friesians with 190 followers and operates a split block-calving pattern, with cows calving from January until March and again from July until October. To simplify calf management, replacement heifer calves are born in the autumn block, with the spring calvers served to beef.
Cows typically graze for seven to eight months of the year, but heifers can be outside from April until January in a good year. Lungworm and roundworms have previously been a challenge due to the extended grazing season, and sometimes treatments were administered too late, impacting growth rates, age at first calving and future milk production.
After weaning, calves are initially moved to a youngstock unit a few miles from the home farm, where they graze land, but are without handling facilities.
Youngstock graze away from the home farm, with no handling facilities
Avoiding stress
“Previously, when we used drenches and pour-ons, we would have to treat every three to four weeks,” recalls Andrew. “To avoid stress from gathering and handling, youngstock are now injected with a long-acting wormer around turnout.”
Calves need to develop immunity to gut and lung worms over one to two grazing seasons to minimise losses from infection. Starting the first grazing period in good health is key to allowing protective immunity to develop effectively at grass. Cydectin 10% LA Solution is a single-shot injection containing moxidectin, used to treat and control gastrointestinal roundworms and lungworms in cattle. It allows animals to develop a natural immune reaction when exposed to larvae, as larvae pass through the gut wall before being killed by the
wormer, initiating immunity.
“We have used the injection in our heifers, and it has been very successful,” says Andrew.
Monitoring and testing
“It’s simple to administer, and I know the calves are covered for a few months rather than having to treat them every few weeks during the summer. Faecal egg counts are also taken to monitor roundworm levels and future field burdens. Although faecal sample testing is less useful to confirm lungworm in acute disease, it is still important to know it is present on the farm,” he adds.
“Since using the injection, we have had more consistent growth rates during the grazing season, whereas we had a lot of ups and downs with the previous worm control. The youngstock have been ready to serve earlier, reaching our target of 350kg liveweight easily by 15 months. Having a robust, joined-up approach to parasites, supported by our vet, is aiding youngstock performance and ensures they are on track to
calve at the 24-month target.”
However, during the grazing season, flies can pose another issue and can cause major economic losses through reduced feed intake and disease transmission. Conditions like pink eye and summer mastitis can potentially spread among animals, having serious consequences for health, welfare and future productivity of dairy heifers. “Historically, we always had one or two cases of pink eye, mastitis and blind quarters each year due to flies. We used Flectron ear tags in a block of first season grazing heifers and second grazing season bulling heifers for the first time during 2025,” says Andrew.
“Tag retention was excellent, so once they were in, they were in.”
“We noticed very little fly activity and fly-related behaviour in the two groups that were tagged throughout the season. There were a lot more flies in the other batches of cattle, as there may have some delays with our spot-on treatment because of other activities on the farm. There were no cases of pink eye or summer mastitis in those tagged and no blind quarters in heifers after calving, which was an excellent season outcome,” he says.
“One tag per heifer, set early, carried us right through to the end of the grazing season, and tag retention was excellent, so once they were in, they were in. While the cost of the tags may be similar to multiple spot-on treatments throughout the grazing season, we saved on handling and animal stress of mid-season interventions. This was a good option for our heifers, which grazed away from home, especially when
gathering and handling is difficult.”