I hope this article can pass on the benefit of a couple of hundred years of collective wisdom.

A pre-lambing drench is a time-honoured tradition, aiming to ensure that lambing ewes, whose immunity to parasites drops just prior to and after lambing, do not contaminate the paddocks with worms.

Wormy lambing paddocks can reduce lamb growth rates, ewe productivity and even lead to deaths if the levels of contamination are severe or barber’s pole worm is present.

Some of the research on prelambing drenches shows that, at least under the circumstances of the trial, they were of little benefit.

However, colleagues, including Bill Johnson from Goulburn, mentioned disasters where ewes and lambs have died in heavily contaminated paddocks without the benefit of a long acting drench.

This year many producers, having been bitten over the last year or two, are using long acting drenches and capsules before lambing.

I think we agreed that mature crossbred ewes in fat score three or better, with a low worm egg count (less than say 100 -200), going onto pastures that have been managed for low worm contamination, with plenty of feed on offer may not require a prelambing drench.

An added proviso is that the lambs are weaned and drenched onto fresh, ‘worm free’ pastures at about 12 weeks of age.

Well-prepared lambing paddocks are either spelled or grazed by cattle for four to five months prior to lambing.

An alternate strategy, termed ‘Smart Grazing,’ developed by veterinarians at Melbourne University, relies on using stock such as wethers or dry ewes that have been drenched with a highly effective drench, to graze lambing paddocks for periods of less than 30 days early in the season.

However, many producers have not or cannot prepare paddocks suitable for lambing especially if they run an all ewe flock.

Paddocks that have been used to graze lambs during the autumn or winter for example, are likely to be heavily contaminated and therefore a risk to ewes and their lambs.

Therefore ewes lambing into risky paddocks that may be contaminated with worms or have limited feed on offer, ewes in poorer condition (less than fat score 3) and ewes from which the lambs will be weaned older (say 4-5 months), should be drenched. A short acting drench may suffice under some circumstances, if low worm-risk paddocks have been prepared, but if several risks are present then a long acting product is required.

The message I got after discussing this issue with colleagues is that sheep producers should plan to lamb in well-prepared paddocks.

A crucial part of this planning is to consider the worm status of the stock grazing the paddock up to five months before lambing.

A second part of the plan, at least in our moister environment, is to administer two summer drenches.

This is a key strategy in reducing the worm population the following autumn, winter and spring.

Long acting drenches are valuable in seasons such as this but cannot be relied on as a longterm solution because they will increase the development of resistance.

I will talk more about the first summer drench in a couple of months.