LAST week I mentioned that we have no evidence that summer drenching benefits young cattle.
However, for sheep producers, the first summer drench is the cornerstone of worm control on the tablelands.
I would like to remind you of research conducted by then CSIRO scientist Dr Norman Anderson 40 years ago.
Norman placed previously worm free lambs onto pastures for a month before replacing them with the next group of lambs. He then killed the lambs and counted all the worms inside them. He found that these lambs picked up plenty of worms each month from April until mid October. However, after this they picked up few worms.
I understand that this is because worm larvae migrate from dung pellets onto grass blades (where they aim to be consumed by sheep), in droplets of water. So even if it is still green, from now on, low humidity and longer days are unfavourable for worms on pastures.
This research was conducted in Western Victoria, an area that usually receives less summer rain than here. However, I think the principles still apply and provide the basis for our recommendation that sheep should receive a ‘first summer drench’ now.
This drench is easy to administer for hoggets and dry sheep but can be a challenge for ewes with lambs at foot.
Many sheep producers on the tablelands will wean in a couple of months. This is a bit late for a first summer drench unless a highly effective pre-lambing drench was given and worm egg counts at marking are low. So the first summer drench is often given at lamb marking.
This creates an additional job on a busy day but may provide the best opportunity to schedule this drench appropriately. As I have mentioned before, under most circumstances it is not necessary to drench lambs at marking. The aim is to substantially reduce the worm population, not achieve the impossible of killing every worm.
Our choices for a first summer drench include firstly combination drenches containing abamectin, levamisole and a BZ, second, monepantel (Zolvix) or thirdly a combination drench containing an organo-phosphate (OP).
OP combination drenches must be used with caution, with care taken to follow the directions given on the label. These include administering the correct dose rate to sheep that aren’t debilitated or don’t have liver disease and have not been held off feed and water.
The OPs, while not particularly effective when used alone, are often highly effective in combination and most importantly will kill most worms that have survived previous drenching with mectin drenches.
I think they have an important role in managing drench resistance and should be considered in the rotation of most sheep producers.
On the subject of OP combinations, Jurox Animal Health has just released NAPfix, a liquefied combination of naphthalophos, abamectin and albendazole. This new combination will be an option for your first summer drench.
Now is a good time to ensure that the drench you use is effective. If you check the worm egg count before drenching and 7-10 days after drenching, you can determine this.
Finally, if you are in a fluke prone area I suggest that you also request a fluke egg count. If you have evidence of fluke, you can then use a combination drench that will also control fluke, such as the four-way combination Q drench.