From the moment ruminants start eating grass, they can be exposed to worms. Worms are ubiquitous, especially in paddocks previously grazed by other ruminants.

When larvae (young worms) or worm eggs are ingested by a ruminant (their host), they follow the digestive tract to settle in stomach or intestines. Eggs will then hatch and larvae will share meals with their host and reproduce. These eggs will then hatch and the cycle will start again. Some eggs and larvae end up exiting the digestive tract to the outside world to be ingested by other hosts.

Higher numbers of worms will naturally absorb more of the host’s nutrients. On top of this, the worms damage the intestinal tract by burrowing into it. Both of these factors result in weight loss – less nutrients are available and absorption capacity is reduced due to damage.

The longer the worm infestation continues, the more damage will be done. On top of weight loss, you can see diarrhoea (once again to do with reduced absorption), lethargy (no energy), animals going down (they start breaking down their own muscle to retrieve energy) and eventually even death.

It’s imperative therefore to have a management plan in place. The simplest way is to have a drenching programme for your stock.

Simply put, there are 3 ways to drench an animal:

Oral drench

a liquid that is injected into the mouth with a special drench gun (no needle). This is the best and cheapest method, however it can be quite labour intensive. The drench directly ends up in the place where it is needed without much loss of efficacy.

Injectable drench

An injection under the skin that is absorbed slowly into the bloodstream. This is less effective and more costly than an oral drench, but still good uptake and efficacy.

Pour-on drench

A liquid is poured onto the back of the animal in a long line over the spine. This then gets absorbed through the skin and into the bloodstream. This is the least effective and most expensive method, however it’s very easy. Some issues with this type of drench is that animals can lick it off, it takes a while to be absorbed and rain can impact on uptake.

For young lambs and calves (3 – 6 months) oral drenches are recommended to ensure efficacy, because they are so sensitive to worm burdens. Drenching frequency varies depending on farm history and pasture management. Stringent drenching is done every 4-6 weeks.
Good news, adult cattle and sheep develop immunity so they don’t need a drench as often.

Goats however need drenching at any age – ask your vet about options, because there are no ‘licensed’ worm treatments for goats.
Please don’t underestimate the damage that can be done by a worm infestation. Apart from severe growth checks, it can result in stock losses and animal suffering.

Pasture management is also a tool to reduce exposure and uptake of worms; your vet can tell you more about this and help you set up a drenching programme.