Oral vs Injection vs Pour-on:

• Oral drenching is accurate and direct to internal worms (no coverage for external parasites) and generally safest for young calves, injectable drenches always deliver a reliable dose for internal and most external parasites, and pour-ons are generally formulated in higher concentrations to try and deliver as good a dose as possible- but there is a risk some runs off before being absorbed. Pour-ons are direct to external parasites.

Which product:

• Drench requirements change throughout the year. Early in the season, oral drenches are safest and solely target gut worms (e.g Arrest C, Switch C). There is a new drench on the market Turbo- that will target gut worms, and another pesky parasite called Coccidia.
• As the season progresses, Lungworm may become an issue – requiring an ML or 'ectin' in their drench (e.g Dectomax, Eclipse E inj).
• After the calves reach 100-120kg pour-ons can be safely used, and from 120-150kg a single (Alpheus) drench capsule can provide 125 days protection.
• From early autumn Cooperia can sneak up on them, often requiring Levamisole in the drench combination.
• As the months cool off external parasites like lice will need to be considered, and a good clean out drench to ensure Ostertagia doesn't hideout and give them problems in Spring. Consider Eclipse pour-on or Boss pour-on (which can be used in the rain!)
• Every farm has its own unique population of animals and worms so there is never a one size fits all when it comes to drenching stock. A combination product is recommended to be used as often as possible.

How often:

Don’t repeat a drench any earlier than 28 days – this is to do with the lifecycle of the worms and allowing a new generation to be exposed to the drench. Going earlier than 28 days will place unnecessary pressure on that drench on your farm. If the stock ‘need’ a drench that soon (less than 28 day interval) then a few other things need to be considered. Was the earlier drench effective? Or what else can be done management wise to reduce the worm burden.

If there is little grazing pressure, long grass, regular shifting, lots of space etc – then the stock could go well over 4 weeks without needing a drench. In young calves, a faecal egg count (FEC) is the best measure to say when the next drench is actually required.

A general rule can be based on the product used. Oral drenches provide no persistent activity – they essentially go straight through. When there is constant worm exposure, 28 days or 4 weekly drenching is a good idea.

Dectomax is a long-acting injection that provides the longest protection of orals, injections and pour-ons. The other injections (usually eprinomectin based) and pour-ons (often abamectin based) fall in between this and the orals.

Ideally, 6 weekly intervals would work but again it depends on what is happening on farm. Often these products need to be used more frequently.

A really good tool for stock grazing a long way from home is the Alpheus drench capsule, which has by far the longest interval of use. As mentioned above, these will provide 125 days of protection!