Thursday, July 7, 2022

Smart drench behaviour

The national survey of the level of drench resistance on New Zealand sheep farms in 2005 served as a wake-up call for the industry.

The situation was much worse than expected. It was a case of as long as we did not look hard enough there was no problem – but when we did look hard, it caught us out.

The outcome was the development of the Wormwise brand, a flurry of scientific studies to prove theoretical solutions, and in general a change in farmer behaviour. Since that survey much more testing has been done, the results of which suggest that that survey underestimated the size of the problem. It is not hard to find a farm with resistance to two or more drench families and even the combinations of these.

What is comforting in the sheep industry is that we have scientifically-backed processes that we can put in place on sheep farms that will effectively delay or slow the continuing development of drench resistance. The big challenge, still, is that not enough is being done on farms to put these processes in place.

A starting point is to know how well each drench family is working on a farm. Any actions depend on having this information. Yet fewer than 10% of sheep farmers have had one of these tests done. I have total confidence that I can advise farmers on how to manage the worms in their sheep in a way that will keep their effective drenches as effective for many years. We know what to do.

At the same time as that survey was done on sheep farms it was also being done on breeding and finishing beef farms. The results from that part of the survey were maybe not as robust as they were for the sheep, but were just as startling. On 94% of the farms tested there was failure of at least one drench family. It confirmed what we were experiencing in the field, which was the failure of the macro-cyclic lactones (MLs) to be fully effective against Cooperia. It also showed up a disturbing level of failure of the BZ family.

What has been the outcome from these results? No change in farmer behaviour, continued use of drench families that probably are not fully effective, and heavy advertising of drench use in ways are that are intuitively not sustainable.

So few drench tests have been done on cattle farms that confirmation of the survey results or even adding to those results, as has been the case with sheep, has not been possible. Furthermore, little research effort has been put into cattle. The recent revelations about the failure of pour on and injectable MLs is visible because there has been so little other research to accompany it.

When we look at the cattle industry it is in a much more precarious position than the sheep industry, yet the industry’s response has been mute. On a large number of cattle farms there is a total dependence on levamisole to manage Cooperia. No other drench family is fully effective. A small amount of testing done on cattle farms, admittedly targeted because of poor results from drenching, suggests that ML failure against Ostertagia could be more widespread than we think. The only tiny amount of drench testing on cattle farms may be supporting the concept of not having a problem if you do not look.

Given that we now know that the route of administration of some drenches can have a big influence on how well they work, and that we know that the use of administration routes associated with lowered effectiveness are widespread in the industry, it is highly likely that many farms are suffering production losses by using drenches that are not fully effective. We do know the production costs of using drenches that are not fully effective. They are big.

What is disturbing in the cattle world is the lack of research effort. While we can extrapolate concepts from the sheep systems into the cattle systems, there are big holes in our knowledge. Diagnostically it is hard work in cattle using the present tools. The refugia tools in cattle systems may need to be different than for sheep. The epidemiology of cattle worms in their free living stages are not as well known as they are for sheep. This affects the management tools we might use.

While the lack of knowledge is a big obstacle, we know enough from sheep systems to apply this to cattle systems and make a difference, but the uptake of any sustainability messages is appallingly poor. The dairy industry is not helping this situation at all and must be part of any initiative to both improve the knowledge base as well as the uptake of smart behaviours.

We desperately need more research on managing worms in cattle systems. I do not have anywhere near the same level of confidence that I can advise cattle farmers on how to manage the worms in their cattle in a way that will keep their effective drenches as effective for many years. The economic consequences of not getting it right are huge, largely because of the impact on the dairy industry, but the needs of just the beef industry are enough to justify significant research investment. 

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