To WormMail mailing list (~ 400 subscribers; recip. undisclosed). WRML.2014-04-16
In this issue:
Resistance vs resilience.
Also: fasciolosis in humans; FWEC course in Tamworth (and elsewhere); Jet lag – there’s an app for that; Phubbing; Easter Road Safety; Moron multitasking.
Resistance vs resilience
Host genotype has a big impact on worm control. A question that sometimes arises is, ” should I select sheep for resistance to worms, or resilience?”
The following, a media release from the Sheep CRC, addresses the question.
“Breeding for resistance best insurance against worms
Sheep breeders pursuing worm ‘resilience’ rather than ‘resistance’ could be placing undue pressure on their sheep during the current dry seasonal conditions.
According to Executive Officer of the WormBoss program, Dr Lewis Kahn, sheep breeders selecting better grown sheep are indirectly selecting for worm ‘resilience’ but this does not improve worm ‘resistance’ because they are separate traits.
“Resilient sheep are those that grow and perform well despite infection from parasitic worms, whereas resistant sheep have a lower level of worm infection because of a better immune response,” Dr Kahn said.
“Resilience is difficult to measure because it is the difference in production between worm-free and when infected, and represents the cost of worm infection.
“And while resilience in sheep is desirable, it has a very low level of heritability, with little benefit passed to the next generation of the flock.”
Dr Kahn said worm resistance was considerably more heritable and could be improved by using Australian Sheep Breeding Values (ASBVs) for faecal worm egg count (WEC).
“Where producers are selecting sheep for production under normal levels of worm challenge, research has demonstrated that this will also select towards worm resilience,” he said.
“In contrast, worm resistance doesn’t come from selecting for production and needs to be separately considered.
“While ‘resilient’ sheep may be little affected by their own worm population, the worm eggs they deposit in faeces onto pasture provide contamination attacking the susceptible sheep.
“And when the chips are down and feed is short, like it is in many areas at the moment (February-March 2014), resilience is greatly diminished and these sheep are less able to cope with the additional stress of parasites.”
The WormBoss program was developed in 2005 by the Cooperative Research Centre for Sheep Industry Innovation (Sheep CRC) and Australian Wool Innovation (AWI).
Since then the WormBoss website, www.wormboss.com.au, and the WormBoss training workshops have been delivered to producers and industry advisers to help industry to reduce the cost of worms through tactics including grazing management, breeding for worm resistance, managing for production targets, using effective drenches and managing drench resistance.
“Commercial sheep producers can identify candidate sires for purchase based firstly on the productive traits they need and then from within this group purchase those with the most negative WEC ASBV. This ensures both productive and worm resistant sires and excludes those sheep where resistance comes at the expense of production,” Dr Kahn said.
It’s an approach supported by the President of the Australian Association of Stud Merino Breeders, Phil Toland, who said that while more research was needed into how sheep and worms interact, the current evidence was clear that the best insurance for a sheep flock against worms was to breed for resistance.
“I hear breeders saying they have sheep with high egg counts that are their best doers in their flock and are therefore resilient to worms, but there could be other reasons why that sheep is a good doer,” Mr Toland said.
“For me the bottom line is that resilient sheep might cope pretty well with worms, but they are still breeding worms which will affect the weaker sheep in the flock, whereas resistant sheep won’t support worm populations.
“Because resistant sheep are not facing this additional stress on their bodies, these are sheep that are more likely to do better in dry times.”
Mr Toland runs Toland Merinos, at Violet Town, Victoria, an 800-hectare property with an average annual rainfall of 625mm. The local environment is suited to the parasitic worms Teladorsagia (small brown stomach worm) and Trichostrongylus (black scour worm).
Mr Toland has been taking worm egg counts on his 4500-head flock, which includes 1200 stud ewes, for more than 10 years, while at the same time selecting heavily for worm resistance as part of the breeding program.
“As well as selecting rams with a negative WEC ASBV, we cull heavily for animals showing scours or dag,” he said. “Breeding for resistance can take a long time, but we’ve noticed with our flock that animals with high or positive WEC scores are often the first sheep dirty with scours.”
Mr Toland said that his worm populations have declined dramatically and his reliance on drenches has been greatly reduced delivering significant savings in terms of dollars, time and labour.
“At the end of the day I want sheep that are both resistant and resilient – that is, I want sheep that don’t carry worms but can also cope with life’s stresses and strains and remain productive,” he said.
· For more information on breeding sheep for worm resistance visit www.wormboss.com.au.
Media contact: Janelle Holzberger on 02 6773 2927″
The media release above (used here with permission) was prepared by Michael Thompson for the Sheep CRC and edited by Assoc. Professor Dr Lewis Kahn (Executive Officer of ParaBoss) with input also from Dr Brown Besier.
The article, large parts of it at least, appeared as part of a bigger piece by livestock editor Jaimie-Lee Oldfield in The Land newspaper on 10 April 2014.
Bear in mind this is a newspaper article, not an exhaustively accurate scientific treatise on the subject. Still, it is of value for persons like myself who have short attention spans, and for others.
Fasciola in humans
I was looking for information on watercress (I didn’t know it was a Nasturtium) and fasciolosis in humans and came across this:
‘Quite interesting really, and not too long. An excerpt: “People can protect themselves by not eating raw watercress and other water plants, especially from endemic grazing areas. “.
I know of at least one human case of fasciolosis in the New England region associated with consumption of watercress harvested from a creek on farm.
Some have suggested that ‘wild-harvested’ watercress can be rendered safe (from parasites for example) by rinsing then soaking in dilute hydrogen peroxide (http://foodfacts.mercola.com/watercress.html). This, in fact probably just thorough rinsing, may work for nematode larvae, but I have my doubts regarding the infective stages (metacercariae) of Fasciola as they encyst onto herbage.
Related: https://wormmailinthecloud.wordpress.com/2011/02/01/wormmail-20110201-trichostrongylosis-in-humans-redux/ (Yet another reason that real man eschew salad).
May 21 Tamworth.
For more information, including other dates and locations:
For even better information or to register call Cassie Gardiner 6763 1276 or Julie Chapman 6763 1285 or email [email@example.com].
Phone app trains you to beat jet lag › News in Science (ABC Science)
Phub not lest you be phubbed? 🙂
Murcott’s Easter Road Safety Message
http://tinyurl.com/murcott-road-safety ‘Worth a look (it’s only short). (Actually, in motorcycle training we are taught 3 seconds back (in the dry) and 4 seconds (in the wet))
Moron more on multitasking