Dry offers no break from worms
Although worm egg counts are often lower in a drought, sheep can become very wormy, very quickly for a number of reasons
Woolgrowers are reminded by the WormBoss program not to become complacent about internal parasite management just because of dry conditions. Stephen Love, state coordinator for internal parasites at the NSW Department of Primary Industries and NSW representative for the AWI and Sheep CRC-funded WormBoss program, says that generally worm egg counts will be lower in a drought, but occasionally sheep become "very wormy, very quickly".
"This can be due to management changes, declining immunity and localised weather events, such as short sharp showers, which can produce localised run-off and a fresh batch of infective larvae – and green pick – over parts of a paddock," Dr Love says. "It's particularly the case for round worms. It is also well known that in dry times in liver fluke country, sheep will spend more time foraging in flukey parts of a farm where there is still some green feed."
Some worms are better than others at handling dry conditions, for example small brown stomach worm (Ostertagia) and thin-necked intestinal worm (Nematodirus).
Also, when conditions do turn good, some worms can quickly take advantage of this, for example, barber's pole worm (Haemonchus) because of its ability to rapidly multiply.
"Sheep at this time can also be more susceptible to worms because of nutritional stress in dry conditions or physiological status, such as late pregnant or lactating ewes, or young lambs," Dr Love says. "One of WormBoss's main aims is to educate woolgrowers about how financially detrimental worms can be in terms of livestock performance.
"The health of the sheep is one of the easiest inputs into wool production to manage, but some growers still fail to give it the level of attention it deserves."
In dry conditions, WormBoss recommends that wool producers:
- keep up regular worm egg-count monitoring;
- be guided by general worm control guidelines for their area and expert local knowledge;
- check on the effectiveness of drenches used – if a full-blown drench-resistance test has not been done recently, at least do a DrenchCheck (a simple worm egg count 14 days after a routine drench). If long-acting drenches are used, a second worm egg count 28 days after treatment is also recommended; many farmers are unwittingly using drenches that have become ineffective due to worm resistance; and
- use grazing management – for example, spelling or rotational grazing with cattle – to avoid excessive worm challenges for susceptible classes of sheep.
WormBoss recommends four general management practices:
- monitor worm populations using worm egg counts to detect infestations early;
- perform regular drench-resistance tests so you know which drenches are effective on your property;
- maximise the use of non-chemical management strategies; and
- seek professional local advice to fine-tune your worm control program.
The WormBoss website offers livestock producers information on worm egg counts, pasture larvae surveys, drench resistance and good management practices. It also features ‘Ask the Boss', which allows users to ask a question regarding internal parasites in sheep and obtain advice on which steps to take.
Producers can also register to receive monthly Worm Updates via email newsletter, with up-to-the-minute recommendations and research results.
More information: See related article 'Worm counts add up to money saved' or visit www.wormboss.com.au or www.wool.com.au/ipm
See also: published in conjunction with this edition of Beyond the Bale is the 'Battling the Blowfly' supplement.
Return to Beyond the Bale Issue 26 index page.