Results from the three-year trial investigating production responses and the cost-benefit of using long-acting anthelmintics and capsules in ewes around lambing warns farmers that the practice is neither predictable, consistent nor necessarily profitable, trial manager Chris Garland of Baker & Associates said.
Six treatments were trialled on 4100 ewes in 14 trials on eight commercial farms over two seasons. A further year was funded to analyse the data, designed with an overview from AgResearch’s Chris Miller and parasitologist Dave Leathwick.
The results have ramifications for farmers poised to apply CRCs to pregnant ewes at scanning time over the next few months. The study found 47% of the anthelmintic treatments resulted in a net financial loss and also that factors other than anthelmintics have a much greater influence over production outcomes – for example, lamb survival or the existence of trace element deficiencies.
There was no correlation between ewe body condition score (BCS) and the production responses from any of the anthelmintics. That is, heavy-conditioned ewes responded the same as light-conditioned ewes.
This is not to say that a production response that lifted an under-conditioned ewe (BCS 3) won’t yield an economic response. But the trial suggested that low-conditioned ewes will respond to anthelmintic treatment no more readily than well-conditioned ewes.
Given the documented risk of accelerating drench resistance through the use of slow-release capsules and long-acting treatments, Garland said farmers should regard these highly variable and unconvincing results as a warning to be circumspect about the use of these treatments.
He said the overall message at this stage was that sheep farmers should focus on feeding pregnant ewes well, particularly in their third trimester (between scanning and lambing) because ewes with a BCS pre-lambing of 3 or better will be far more resilient to intestinal worm challenge, short-term underfeeding and many other challenges over lactation.
“We have still got a lot to learn about how some farms appear to achieve either a lower parasite challenge in their ewe flocks, or manage their flocks in such a way that those sheep are able to exhibit greater resilience in the face of a parasite challenge over the spring.
“We have not been able to correlate management factors such as feed cover and pasture management directly with treatment responses but we have some valuable leads for further trial work,” Garland said.
- The three-year anthelmintic trial programme was funded by the Sustainable Farming Fund, host farmers, Beef + Lamb New Zealand, Agmardt, East Coast Farmers Council, Baker & Associates, Keinzley AgVet, Farmlands, Ravensdown, LandCorp and Mount Linton Station.
