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Beyond the Bale : February March 2009
8 aniMal health Worm problem I February – March 2009 Beyond the Bale dries up A water conservation scheme delivers surprise worm control benefits t started with a government initiative to save artesian bore water. encouraged to prevent evaporation from open bore drains, the ‘Millencowbah’ sheep properties at lightning ridge, nsW, opted to tank and pipe their artesian water to concrete drinking troughs. surprisingly, however, property manager James ellis noticed that as the drains dried up, so too did their persistent problem with parasitic worms. “before we piped and capped the bore drains, we needed to drench pretty regularly to protect our sheep from worms, even during a drought,” he says. “but as the bore drains were replaced with pipes, we started having much less trouble with worms. We haven’t drenched since 2007 and only really need to do so after heavy rain.” the observation makes sense to Dr stephen love, state coordinator for internal parasites at the nsW Department of primary industries. in an otherwise dry environment, bore drains provide a safe and congenial habitat for worms when they should be at their most vulnerable – as eggs and larvae struggling to survive outside the host. but if drains dry out, especially during a drought, the worms are likely to experience a miniaturised form of catastrophic climate change. to aWi’s Dr Johann schröder, the ‘Millencowbah’ experience is an interesting example of a mainstay strategy within integrated pest management (ipM). he calls it ‘habitat manipulation’ and is referring to those on-farm practices that create hostile environments for free-living worms that prevent them from re-infecting sheep. Under existing ipM practices, Dr love says the most common examples of habitat manipulation involve cropping grazed paddocks and alternating grazing by sheep with cattle, since the parasites of these two animals tend not to overlap. as for on-farm bore drains, since 2002 four of the ‘Millencowbah’ properties have been piped and capped at a cost of just more than $1 million. ‘Millencowbah’ owner roger Fletcher says a percentage of land on these properties had previously always been ‘wormy’, but the difference in worm loads since the drains were replaced is striking. the major impact, he says, was on barber’s pole worm. While the reduction in drenching is a welcome – if unexpected – bonus, James ellis says that the conversion amounted to a fair bit of work. “We had a contractor digging trenches and laying hundreds of kilometres of polythene pipes from the bore head to 20,000-litre water tanks that feed the cement drinking troughs,” he says. the scale of the water conservation project, though, is not out of place at ‘Millencowbah’. roger says there are always new schemes and ideas being trialled on the properties. the latest involves running trains from Dubbo to sydney to carry containers of wool and fleece. “James and i come from different backgrounds to most people,” roger says. “We tend to do lots of things differently.” More information: James Ellis, 02 6829 1683; Dr Johann Schröder, firstname.lastname@example.org; Dr Stephen Love, email@example.com – gio braidoTTi an open bore drain on ‘millencowbah’ prior to the piping and capping water conservation scheme. a dried and filled bore drain following the piping and capping water conservation scheme. The Worm burden While dags, scouring and death are the most prominent damage caused by worms, Dr Stephen Love of the NSW Department of Primary Industries says more than 80 per cent of worm damage is due to ‘subtle’ production loss, such as growth retardation, which can occur even when there are no visible signs of a worm infection. “Worms in livestock are a bit like an iceberg, with the tip easily visible, but most of its mass hidden beneath the surface,” he says. Furthermore, the overall cost to industry is increasing, as worms and flukes build resistance to individual and combinations of drenches. It is a nationwide problem, and Dr Love emphasises that virtually all Australian sheep farms have drench resistance to some degree. “At a cost of $369 million a year, this makes worms the number-one health problem of sheep,” he says. “This is followed by flies and lice, and then footrot.” FighTing back To make the most of available worm-control options, AWI is helping to develop a comprehensive integrated parasite management (IPM) system. The program encompasses all three key epidemiological players: l The parasite. The aim is to identify ways to better target different worms with the right chemical at the right time. l The host. Co-opting genetics and nutrition to build stronger resistance to worms. l The environment. Making the most of farm management options to prevent worms surviving outside the host. cosTs l The annual loss to Australian sheep industries due to worms was estimated in 1995 at more than $220 million. l A forecast in 2000 suggested that drench resistance could see losses attributable to worms reach $700 million within 10 years. l In 2006 Meat and Livestock Australia estimated that losses from worms had increased to an estimated $369 million. than mulesing. the results of the aWi-funded study into mulesing and possible Clips the gentle stretCh For laMbs n ew research shows that clips designed to reduce Merino lambs’ susceptibility to flystrike have less effect on lamb health and welfare alternatives were presented in 2008 at the american College of Veterinary pathology annual conference in texas. an independent team of veterinary scientists from the University of sydney compared the local and systemic health impact of mulesing on young Merino lambs with alternative methods of reducing skin wrinkle and increasing bare breech areas. the study team included senior lecturer in veterinary microbiology Dr Katrina bosward, veterinary pathologist professor paul Canfield, and veterinary surgeon associate professor geraldine hunt. study leader Dr bosward says, as woolgrowers are only too aware, wrinkled skin, dense thick wool and moisture around the breech and tail areas of Merinos are known to create a “blowfly-breeding paradise”. the remaining key issues with clips are whether they significantly reduce lifetime stain, dags and flystrike, and their eventual biodegradeability. overall, the clips had relatively mild local and systemic health impacts when compared with mulesing. the clips produced well-healed linear scars, with reasonable tightening of the skin that may be adequate for the prevention of flystrike. “to the naked eye, the plastic clips have been shown by us and others to significantly reduce the wool cover around the tail and breech – a major factor associated with flystrike in Merinos,” Dr bosward says. taking it a step further, the researchers looked at what was happening deeper in the skin, observing microscopically what effect the clips were having on the skin. “at the same time as assessing effectiveness of the clips at reducing the excess skin around the breech area, we subjectively measured a wide range of variables that indicate the lambs’ degree of discomfort as well as objectively measuring their body’s systemic response to the treatment,” Dr bosward says. subjective measures of discomfort included monitoring appetite loss and changes in behaviour such as tail swishing and reluctance to walk or lie down. More information: www.wool.com.au – kellie penFold photos: JaMes ellis
Dec 08 - Jan 09
April May 2009