Tasmania worms, flies and lice update - May 2020

Sheep at a Bromar feeder, Tasmania

Perth: Paul Nilon, Nilon Farm Health (pandonilon@bigpond.com)

The bumper season continues. Many paddocks are now too wet to work, so those who did not get winter cereals or brassicas planted may struggle to do so. However, with the amount of pasture on offer and the fact that it is still growing with the pace of a thousand startled guinea fowl, it’s unlikely that winter fodder will be as critical this year.

Monty Dwyer, famous ABC Darwin weatherman, had a good way of dealing with the sameness of the dry season weather. Say nothing, unless something worth talking about appears. Same for autumn worms.

Is this right?  A stud client includes WEC ASBVs in his data. Good for him. He noticed that individual WECs for his rising 1-year old ram lambs were skewed heavily towards Nematodirus, with up to 1100 epg of nothing but Nematodirus. In the late summer and autumn it’s not uncommon to have Nem-dominant WECs, particularly if the summer has been dry, but this place is almost perpetually green and, importantly, the sheep were not scouring. Is this possible?  Well, certainly possible, but unusual and unlikely. So, the most likely explanation was that Nem and Strong counts had been transposed (particularly as this property sometimes has autumn Haemonchus).

The point is that WECs are a chancy bit of measurement at the best of times. If you do not get a result that fits with what you are expecting, make sure you check out what’s going on.

Another example was a client expecting a high count, which came back zero. When he asked the technician she conceded that all counts that day had been zero. Likely that the flotation liquid was below the required specific gravity. This is not a finger pointing exercise: just to point out that lab QA/QC can fall down, no matter what lab or operator. Not often, just occasionally!

Go to the WormBoss website to find ParaBoss-endorsed WEC providers.

Editor’s Note: With almost 30% of participating WEC service providers failing to deliver the required accuracy in the 2019 ParaBoss WEC QA Program, producers should check whether their provider is on the list of successful participants laboratories.

Sheep and Goats: The distinction between them sometimes blurs. As you know Australian goats (or at least the non-dairy breeds) derive from desert environments. This makes them vulnerable to diseases of wet and green, to wit, footrot and parasitism. Now, my antipathy to Dorpers, Awassis and some other breeds may give me a biased view of these sheep’s capacity to handle worms. However, what I am thinking of is that a sheep becomes like a goat when its immune system fails to respond to a worm challenge. While there may be genetic differences between sheep breeds in their ability to handle worms, in the Australian context the differences between the breeds can (largely) be explained by the way we run them. The animal determinants of worm vulnerability include:

• Late pregnancy and lactation: the periparturient rise in worms is universal.
• Body condition. This is the biggy. We (still) consistently run our Merinos at lower body condition scores (BCS), particularly while they are young.
• Nutrition going forward: even if BCS is light, sheep with good nutrition, particularly protein nutrition, combat worms better than light sheep with no tucker on their plate.
• Intercurrent disease: worm burdens feed into themselves. Diseases that reduce grazing and BCS aid parasitism. Sheep with Johne’s disease carry huge worm burdens.

So, if all this is self-evident why do we have such problems controlling worms in Merinos, particularly the youngens?