Gippsland - How Now Gippy Now - May 2010 Edition
To drench or not to drench?
By Lauren Conochie
Drench resistance is now recognised as an important problem facing cattle producers, and has been identified on dairy farms in Gippsland.
Frequent treatment designed to prevent worm burdens altogether is likely to result in drench resistance in a relatively short period of time. Worms cannot be eradicated which means we must learn to farm with them.
All farms are different, and no one set of rules can be applied to every farm. Sustainable integrated parasite management is a complex topic beyond the scope of this article, but at least it might encourage you to discuss it with your veterinarian or farm adviser on how it could apply to your farm.
When to treat?
Given adequate exposure to low level worm burdens, cattle will acquire a degree of natural immunity to worms in their second year of life. Over-treatment of calves will not allow this immunity to develop and older animals will require extra treatments – a vicious and expensive circle!
The frequency of drenching required by calves will depend on their environment. A heavily stocked, irrigated paddock used for calves every year is likely to have a much higher number of worm larvae present than a large block where older animals are run and the area is cut for hay/silage or caropped as well.
Worm larvae live on pasture and need moisture to develop – calves do not need drenching until they have been eating pasture. In very dry periods where no pasture is being fed, worm burdens should be low.
Individual animals vary in their susceptibility to worms, so close monitoring can usually detect a worm problem early on when a ‘tail’ of poorer-doing animals begins to develop in the mob.
Consider using worm egg counts of faeces for regular monitoring. If a drench is due and there are no signs that it is needed, then it probably isn’t. Continue monitoring instead and save your time and money! The number of drenches required may be less than you think.
Is it worms?
Most drenches available now (except white drenches) have persistent activity and drenching at an interval shorter than six weeks should not be required.
If you have calves scouring despite being drenched recently, veterinary advice should be sought. It may be a drench resistance problem or something else. There are circumstances where a sudden high intake of worm larvae can cause a rapid onset of signs despite a low worm egg count.
Think also about other causes for scouring – Yersinosis, Coccidiosis (black scour), low level grain overload when self feeders are used. Allowing back-grazing on recently grazed paddocks or a lack of fibre in the diet can also look remarkably like a worm problem.
Paying attention to proper nutrition of your calves will pay dividends in building their innate resistance to disease and result in bigger, happier heifers when they join your milking herd, as well as reducing your drench bills.
Choosing a drench
Although pour-ons are convenient, research has shown that much of the drench uptake actually occurs by licking. Therefore within the mob, some animals will be getting too high a dose and others too low. You may also get residues and undesired effects in untreated animals. Oral and injectable products, although harder to find, are far better as you can control the exact dose each animal gets.
Don’t use a combination product for liver fluke and worms if you don’t need to treat both – over-treatment is a fast track to resistance problems.
Don’t forget the basics…
- Weigh animals or use a weigh band (most farmers underestimate weight).
- Dose for the heaviest animal in the mob.
- Test your equipment every time to ensure it delivers the correct dose.
Contact:
Dr Lauren Conochie
DPI Ellinbank
Tel: 5624 2222
