Some fungus spores, like facial eczema, need moisture and dead matter to grow. Photo / Mark Mitchell
Some fungus spores, like facial eczema, need moisture and dead matter to grow. Photo / Mark Mitchell
When I was a kid Dad would tell us a long, rambling story, which went from one good thing happening to a bad thing, to which the crowd of kids in the car would alternate between shouts of ‘yay’ or ‘boo’.
Rain coming after a drought is a classic scenariowhich creates an ideal environment for both good and bad things to happen – but farmers need to be careful they are not just telling themselves a story!
On the one hand, dry weather is not great for the survival of much. Our story starts out with a ‘boo’ because there is not much feed around and stock and their owners are doing it hard. The good part of the story is that some fungus spores, like facial eczema, need moisture and dead matter to grow – so they have a hard time too.
We have seen some moderate to low spore counts in some areas this year because there has not been the moisture to allow them to flourish. Also, because the stock ate all the grass down, there was less dead matter to feed the spores. Parasitic worm eggs too have a hard time in the dry conditions and will dry out quicker than when conditions are moist.
Both facial eczema and parasitic worms need grass as part of their lifecycle, so if the stock had no grass and were eating supplements, these diseases would have had a hard time. So, to this, I would say ‘yay’.
However, once the rain falls the story can turn the other way. The grass comes away and we have some feed and everyone is happier - yay - but the worms and spores could get an easier time, and we would say a resounding ‘boo’.
Helping the parasitic worms out might be that stock is eating down into the grass where there are more worm eggs. The cold weather which has limited grass growth of late is another ‘boo’ - but it reduces the growth of eczema spores too - so ‘yay’.
The problem with this story approach is that, while it makes for great entertainment for kids on long car trips, it is not great for animal health planning. You can tell the story if you know it to be true but otherwise you might be making it up. Sometimes the opposite thing happens on neighbouring farms because the management is different.
The good news is that we have tests for both eczema spores and parasitic worm eggs, as well as the damage that they do to animals. Once we know what is happening we can take action to stop losses based on evidence. That might prevent another ‘boo’ story for the coming season.
Keith Christensen BVSc is a mixed animal veterinarian at Levin & Horowhenua Vets
