Drench resistance: The next big issue?

Waikato sheep and beef farmer Matthew Scott believes drench resistance is the next big issue farmers will face.
Tuesday, 29 November 2016

Matthew and wife Hayley farm “Te Koraha”, a 2800ha family property south of Raglan. Alongside an Angus stud, the property runs 5000 Romney and Romdale ewes. 

Six years ago, the Scotts began buying rams from Northland-based ram breeder Gordon Levet, who’s been breeding towards internal parasite resistance for 30 years.

Matthew: “We had a real problem with barber’s pole (Haemonchus contortus) and had to drench the two tooths to get them up to weight for the ram. Since we started using Gordon’s rams, we haven’t had to drench the two tooths at all.”

Lambs now receive one drench at weaning, alongside a long-acting dip, then that’s it until February.

“It’s expensive to drench and, in the back of my mind, drench resistance is the next biggest problem farmers will face. If you’re in farming for the long term – which most of us are – we need to think about how we manage our stock.”

Matthew is also mindful of increasing fixed costs and unnecessary chemical use. 

Ram selection

He places a lot of emphasis on genetic information. “I buy rams with the best data behind them and pay an average of $1800 for a two-tooth ram, which I think is reasonably cheap for what I’m getting.

“They’re good rams. They’re not the biggest rams, but they’ve been raised in a harsh environment. 

“Sometimes, as farmers, we need to step back and think about the conditions rams have been raised in and how they’ve been treated.

“Gordon’s rams bolt away once they get here. They’re also adding ‘toughness’ to our flock – the ewes are a lot hardier. It wasn’t just Barber’s Pole we faced, we had liver fluke as well.”

What next? “We’ll keep moving down the genetics road. Genetics offers huge advantages and is easy to change. And you can have a new generation in your flock within a year.”

The breeder’s perspective

Gordon began breeding toward worm resistance in 1987 and today, 80% of his stud Romney rams are undrenched. He predicts it will take another four or five generations before he has a sheep that is totally bullet-proof against blood-sucking internal parasites. 

Gordon has observed the drench-based strategy to worm control over six decades and has two major concerns. “Even the most susceptible sheep will thrive with regular drenching – and many will be retained as replacements. This means the national flock is becoming increasingly more susceptible to worm challenges, over time.

“Secondly, thanks to drench, we have a breeding programme for encouraging ‘super worms’, because the 99% weakest worms are regularly eliminated.”

The ultimate outcome? “A dead-end road where we are breeding ever more worm-susceptible sheep, that are being subjected to ever more ‘super worms’.”

Gordon says the trend for farmers to look towards genetics to reduce the impact of facial eczema long term is heartening. “Should we now consider that there is a genetic solution to the worm problem also?”

Resources for farmers