Learn about how different farm systems and policies set up different levels of risk – both for worm challenge, and for drench resistance. We also highlight some management ideas and risk mitigations.
Good nutrition is #1
No matter what systems are in place on a farm, very good nutrition greatly reduces the risk of worms to stock. Conversely, farms where underfeeding is a feature, frequently have issues with worms.
- Watch this video on risky systems.
- Listen to this DairyNZ podcast: better worm management for healthy heifers.
Cattle system or policy
The tables below show you the risks, along with suggested mitigations, for worm challenge, and drench resistance in different farm systems.
Beef breeding with most calves sold at weaning
The risk of calves creating high cattle worm challenge is low. Calves are typically only a small percentage of the stock on the farm and don’t usually get wormy while on their mums.
Risk would increase if a 100kg dairy beef enterprise was grazing the same area.
Share grazing areas with other stock classes. Keep weaners on high residuals. Winter crop can be useful low parasite challenge feed.
Risk is low in systems with good feeding and low drench use. Risk could be higher with a big component of purchased 100kg dairy beef with poor management and high drench use.
Because worm challenge is low there should be no need to treat calves while on mum.
Individual cows in low body condition or under stress may sometimes require treatment but this should not be an annual feature. Unlikely to worsen drench resistance.
Beef breeding with 1Y cattle finishing on same feed platform
Weaned calves are the source of pasture contamination to the following years’ calves. This is exacerbated if 100kg dairy beef are part of the R1 stock mix. If finishing cattle are bought-in at an older age, the risk drops.
Look for ways to use adult cattle as ‘vacuum cleaners’. Keep weaners on high residuals. Winter crop can be useful low parasite challenge feed. If dairy beef calves are part of the mix, avoid having them in the same area all the time. Especially in the early months.
Risk could be higher if cows and calves shared grazing area with100kg dairy beef with poor management and high drench use.
Good nutrition to grow R1s fast and minimise parasite uptake. Avoid over-drenching. Use of TST and extending drench intervals when safe can aid this.
Finishing system purchasing cow-reared weaners
If these weaners are well fed and share grazing areas with sheep and older cattle classes, the risk is low. It may be increased if they are always run on the same area of permanent pasture and nutrition is poor.
Share grazing areas with other stock classes. Keep weaners on high residuals. Winter crop can be useful low parasite challenge feed.
Generally these calves arrive on-farm in autumn and receive a small number of drench treatments - there is little selection pressure for resistant parasites to develop.'
Good nutrition to grow R1’s fast and minimise parasite uptake. Avoid over-drenching. Consider using TST and extending drench intervals.
Finishing system purchasing 1Y+ animals
Generally low though worms could still impact production if nutrition is poor.
Use appropriate quarantine treatment protocol and feed animals well.
Animals over a year of age are not big contributors to pasture contamination. Worms that survive treatments in these animals don’t produce a lot of viable eggs.
Don’t under-dose, choose oral or injectable formulations.
Finishing system purchasing 100kg dairy beef weaners
Where these cattle are the main stock class, worm challenge can be very high. Where they share their grazing areas with other stock, or are on crop, it can be lower.
Calves will perform much better where they are offered low worm challenge feed: pasture grazed by sheep or adult cattle for several months, new grass, crop, hay/silage aftermath. Feeding calves a high ME supplement also helps them grow fast and resist the effects of worms.
Risk is high when calves are grazing permanent pasture only and drench is the only worm management tool. Risk also increases if calves are drenched and shifted onto low worm challenge areas such as new grass paddocks.
Avoid over-drenching. Consider using TST and extending drench intervals once calves are big enough to cope with these strategies. Change system if it’s all calves on permanent pasture all of the time.