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Strategic Worm Drenching Saves Money

Strategic drenching of all sheep with a double summer drench (November/December and January/February), with a move to 'low risk' pastures has been recommended for many years.

By Department of Primary Industries - 1st March 2006 - Back to News

This is to take advantage of pasture drying and the consequent destruction of worm larvae by lack of moisture and exposure to ultra violet light. Worms occur either on pasture or in the animals. The drench fixes the animal problem and the environment the pasture problem.

In drier climates, a second summer drench may not always be necessary. There is, however, no clear guideline as to whether a second summer drench is, or is not, required. This is because poor nutrition, summer rains and other management factors can result in higher worm burdens than might be expected.

The only way to decided on whether to give a second summer drench, is by doing a 'WormTest'. The test counts the average number of worm eggs that are present in each gram of faeces passed by sheep in a particular mob. This is used as a guide as to whether or not to drench.

Mobs with less than 100 eggs per gram don't require drenching. Egg numbers of 200 - 400 per gram could indicate the need to drench but, in some situations, drenching may be put off for another 4-6 weeks, when egg counts can be re-checked.

WormTest kits are available from most DPI offices and private veterinarians. The cost of a basic WormTest is $30 or less. Results are usually available on the same day that the samples arrive at the laboratory.

Samples can be collected for WormTest by running a mob of sheep into the corner of a paddock, holding them there for 10 minutes, collecting 10 samples of freshly deposited droppings and placing them in the container provided. Sampling early in the morning, when it is generally a little cooler, may make it easier to pick out the fresh droppings.

If a second summer drench is to be given, then each sheep must be given the correct dose. The biggest sheep in the mob should be weighed and the dose rate calculated for the heaviest sheep. The drench gun should also be checked to see that it is delivering the amount that it is set to deliver.

Reducing feed intake, but not the water intake, for 24 hours before drenching can increase the effectiveness of certain drenches (ie -mectin type drenches and the white -bendazole drenches). This is not recommended for heavily pregnant sheep, stressed sheep or sheep in poor condition.

After drenching, sheep should be moved to 'low risk' pastures. Typically these are paddocks previously grazed by cattle, older wethers or dry ewes.

Source: http://gippsland.com/

Published by: news@gippsland.com