ParaBoss News - March 2019 - Feature Articles

Cryptosporidium is a microscopic parasite with a thick wall. Source: CDC, Atlanta USA.
Cryptosporidium is a microscopic parasite with a thick wall. Source: CDC, Atlanta USA.
Drenching: are you doing it right?
Drenching: are you doing it right?
The famous Mexican Hat shaped graph.
The famous Mexican Hat shaped graph.
For a shower dip to work, sheep must get wet, completely wet! Source: Peter James
For a shower dip to work, sheep must get wet, completely wet! Source: Peter James


Fast fact: Can I catch it?

Zoonoses (diseases spread from animals to people) are a fact of life, and most of us are aware of some that make the news (for example Salmonella and Campylobacter may be spread by direct contact but more likely by contaminated food). The list of zoonoses for sheep and goats is way longer than most people realise. While sheep, goats and humans share very few types of worms (a subject for future articles), the protozoal parasites Giardia and Cryptosporidium, rare causes of diarrhoea in sheep and goats, can easily be transmitted to people. So, if you are handling scoury lambs and kids think of zoonotic potential and take precautions: wear gloves, wash hands and don’t smoke.

Feature articles

Drenching: are you doing it right? 

by Paul Nilon, Nilon Farm Health, Tasmania

Should there be a drenching technique course, similar to those for chain saw use and driving quads? Try selling that to sheep producers, although I am sure there are many service providers that would jump in. I suggest that poor drenching technique is very common, it’s just that in most cases we are unaware of it and there are few consequences. >> Read more.

The famous Mexican Hat

introduction by Paul Nilon, Nilon Farm Health, Tasmania 

If you scroll down this link you can see the graph of larval availability to grazing livestock is shaped like the famous Mexican hat. What’s so special? Well, for starters, it may soon have a wall around it (just saying!). Secondly, the larval availability graph is essentially similar for all scour worms in all environments and dictates decisions about the timing of strategic drenches and the time required to produce safe pastures. For the former, we can infer from the graph why we give summer drenches: hit the residual worm population inside the sheep when pasture availability is low (summer) and the time for the worms to get going in the autumn is increased, so winter problems come off a lower base. We can see that a spelling period of a few weeks in the spring and summer may be sufficient to produce a safe pasture due to rapid larval die-off (and lack of accumulation). Conversely, after the autumn break and into winter, there is much greater larvae accumulation, so months of spelling may be required. So study and treasure the Mexican hat.  >> Read more.

The genes have it

introduction by Paul Nilon, Nilon Farm Health, Tasmania 

Changing genotype to manage flystrike is not rocket science. In the best of all possible worlds, you should be using ASBVs for breech wrinkle, dag and breech cover. However, not all studs are on board with ASBVs, and even those that are, do not always publish the ASBVs for these traits. It’s not unreasonable to ask them to wrinkle score their rams, and if they are reluctant to do so, it’s time for some hard thinking. Within your flock you can use visual sheep scores for wrinkle, dag and fleece rot to make your flock more robust. Most of the benefit is for the life of the selected sheep in your flock: there is some genetic benefit, but it is small compared with using rams that have been selected using fly-associated ASBVs. >> Read more.

Are they wet? 

introduction by Paul Nilon, Nilon Farm Health, Tasmania 

Shower dips were once common, but less so now. The fact is that they are fiddly to set up correctly and relatively slow to use (whether for lice or fly) and many just didn't do the job properly. Innovative uses for “retired” shower dips include pig pens and a shower watering system for pot plants. Notwithstanding, many are still in use around the country, and at least one is still made. For a shower dip to work (i.e., eradicate lice from all treated sheep) the sheep must get completely wet. This site gives all the operating parameters for shower dips. How do you know they are working? Mark some sheep with a water-soluble texter at skin level and see if it washes. >> Read more.

What should you select for: Resilience or Resistance? 

introduction by Paul Nilon, Nilon Farm Health, Tasmania

To breed more worm ‘resistant’ goats you can select for resistance or resilience, or both. Resistant goats have immune systems that reduce the burden of worms they carry, and the egg output of any remaining worms. You can select for resistant goats (bucks) by using raw WECs, but EBVs for WECs are way more robust. Patronise stud breeders that have appropriate EBV information. Resilient goats may carry a lot of worms, but the effect of the worms on their productivity is low. FAMACHA is a surrogate measurement for resilience to barber's pole. A range of productivity measures can be used. Now, both traits are moderately heritable, so which is better? This writer will nominate resistance as the better way to go: firstly resistance is quantifiable and can be (indeed, is) built into EBVs, and a bit more hereditable. Resilience measures are much more difficult to quantify. Secondly, if you concentrate on resilience the contamination of pastures can get out of hand, and sooner or later may present your animals with such a challenge that they succumb. In any case, breeders select primarily for production, so resilience is incorporated into a multi-index breeding value. >> Read more.


What are your needs for better parasite management services?
What are your needs for better parasite management services?
Are your worm egg counting results up to scratch?
Are your worm egg counting results up to scratch?


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For March 2019 state outlooks, please follow the links below:

South Australia
Tasmania
Western Australia
Queensland
Victoria
New South Wales