Warrnambool Veterinary Clinic

"We aim to deliver superior veterinary services to our clients and their animals."

Deciding when and if cattle need a drench is an often asked question. A number of factors influence the worm susceptibility of cattle on south western Victorian beef properties. These factors include the age and condition of the cattle, dry or lactating, time of year, feed available and previous grazing history of paddocks.

DO THEY NEED A DRENCH IN WINTER?

* Faecal egg counts are unreliable in cattle over 18 months of age.

No single risk factor should be used in isolation or is more important than other factors. Look at the overall situation rather than concentrating on one risk factor. F.E.C. levels are only a guide, even in young animals. A mob with a low FEC may still need a drench if other factors are high. Grazing pastures at the levels, which make worms a low risk, will also increase pasture production and optimise nutrition.

WHEN SHOULD I DRENCH AND WHICH DRENCH?

The factors above, plus the timing of the drench will also determine which drench group should be used. It may be possible at certain times of the year, to reduce costs by using an oral drench.

*BZ = new generation white drenches such as Panacur, Synanthic etc which are given orally.

ML = Macrolytic Lactone drenches such as Eprinex, Cydectin, Duotin etc etc.

Because white drenches are effective at killing worms in cattle, but are short acting and less effective at killing inhibited ostertagia, they can be used when cattle will be rapidly recontaminated with worms anyway and type II Ostertagia not a threat. The Macrolytic Lactones should be used when control of type II ostertagia is essential and when the sustained action is of greater benefit. This drench group can be used at all times.

Thanks to Dave Rendall for this information.