Growing a Solution

“You cannot drench your way out of the worm challenge problem or drench resistance.

“The sheep and cattle industries are facing a growing drench resistance issue. Our commonly used drench families are becoming less and less effective at killing the common gut worms in younger animals and, in severe cases, adult animals,” says Jason Leslie, PGG Wrightson Technical Expert for Animal Production.

New Zealand’s temperate climate means pasture, such as grass and clover mixes, is a very favourable environment for infective larvae. Because most farms utilise pasture, New Zealand has a high larval challenge during significant periods of the year. Most (50 to 75 percent) of these worms live in the first two centimetres of the pasture sward and top centimetre of the soil. “We have high stocking rates on our sheep and cattle farms. They are grazing in that danger zone all the time, because that is where the best quality feed is. Unfortunately, it is also where most worms are.

Young animals, those in their first 12-months, suffer the most. Their immune systems are too immature to tolerate these worms in high numbers, but older animals can be affected as well,” explains Jason.

Controlling worms does not come down to a single action, but rather a multi-action approach: disrupt the life cycle, reduce the number of worms on the farm, and prevent reinfection. Drenching is just one action point, but one that comes with the risk of resistance.

“We asked ourselves, in the face of drench resistance and high worm challenge, how do you create a sustainable worm management programme? What are the various tools in the toolbox, of which an effective drench remains just one of the tools. Another tool, we believed, could be summer forage crops. We wanted data to back this theory up," explains Jason.

The way grass and clover sward grows creates a moisture-rich environment for worms to thrive. Summer forage crops grow taller and more upright and open than pasture. This allows additional sunlight to reach the crops during the establishment phase, and creates a less hospitable environment for parasites. Until now, the concept of using summer forage crops was more theoretical.

“We had limited supporting data for the modern forage options,” explains Jason.

However, a multi-year trial, conducted in collaboration between PGG Wrightson and PGG Wrightson Seeds shows replacing pasture with summer forage crops is a proven mode of action in the fight against worm challenge. 

“Your brassicas, lucerne, chicory, plantains have a better ability to grow through late summer and into early autumn to provide a high protein, high energy, highly nutritious feed compared to brown dry pasture. It is also a less favourable environment for infective larvae which can delay the need for drenches. We now have the data to prove it,” Jason says.

PGG Wrightson Seeds’ facility in Lincoln, Kimihia Research Centre, was a vital testing ground for the trial.

“Kimihia has the resources allowing us to manage the lambs and forage crops under reasonably tightly controlled conditions,” says Charlotte Westwood, PGG Wrightson Seeds Veterinary Nutritionist.

In addition to Kimihia, the trial ran on commercial farms in ‘real conditions’ around the country across different plots of crops. 

“We extended the trial, in slightly less rigorous conditions at some of PGG Wrightson Seed’s satellite sites, and Jason ran testing on several mobs on commercial farms throughout New Zealand,” she says.

“We were really pleased to see the benefits of forage crops for worm management showing up on commercial farms, beyond the more tightly controlled conditions at Kimihia.”

At each testing site, the timing of faecal egg tests were essential to mapping worm burden. 

“The key timing is 28-days because it is when most farmers are considering another drench. We wanted to see if they had a measurable worm burden requiring another drench. We tagged a group of animals in each mob, 10 of which we checked their faecal samples on a weekly basis out to 70-days. The stock on pasture
reached 500 eggs per gram between 28 and 35 days. The mobs on summer forage crops had extended intervals, with some not breaking through the 500 eggs per gram zone by 70-days,” Jason explains.

Regular faecal egg monitoring after 28-days of grazing forages is crucial to determine the need for further drenching. For Charlotte, this big take away is ensuring your crop-fed lambs do not gain access to pasture.

“The great thing about Kimihia is the ability to deny lambs access to anything other than forage crop. We had lots of spare fencing reels to ensure the crop-fed lambs never got so much as a mouthful of pasture in the whole 70-day trial.”

Cleaning out your paddock, before planting your summer forage crops, is imperative.

“The trick is to achieve an effective spray out of your existing pasture before direct drilling, or best-case scenario, cultivating your paddock so it disrupts the larvae’s environment. Then you need to allow the forage crops to grow, with no stock entering the paddock, to prevent the introduction of new larvae. This takes
somewhere between six weeks to three months, depending on the type of forage crop,” says Jason.

Charlotte agrees, “Any blade of grass will give worms a hiding place. You must have top shelf agronomic planning and monitoring to keep unwanted weeds and grasses out of the base of the forage crop. This is where working with your PGG Wrightson Technical Field Representative can really help.”

For Jason, giving farmers valuable solutions is important.

“When we talk about drench resistance, it is often very doom and gloom. But this is proof we can do something positive to reduce the worm challenge, improve our farm systems, and not contribute to growing resistance.”

Learn more about how you can use summer forage crops to reduce worm burden by contacting your local PGG Wrightson Technical Field Representative.