With many drench options on the market, it’s important to consider which is best for your calves as they grow.
Drenching is an essential element of calf rearing. It allows you to control calves' exposure to several parasites commonly found in our pastures.
When burdened with worms, calf growth rates can be limited by up to 30% due to loss of appetite and poor nutrient absorption. If burdens go unmanaged, they can lead to more severe illnesses, such as parasitic gastroenteritis or bronchitis and pneumonia from lungworm infestation.
It’s likely that having such a wet spring as we’ve experienced this year, and now with it starting to warm up quickly as well, parasite levels in pasture could be much higher than normal. So drenching and faecal egg count (FEC) testing if it’s suspected the drench hasn’t been effective are even more important.
Selecting the right drench for your youngstock at their stage of growth and maintaining a good drench programme are key.
Why should you drench calves and when?
Calves from weaning up to about 15 months old are most vulnerable to worms, as they don’t yet have a well-developed immunity against the different types of parasites.
Usually calves should be drenched for the first time at weaning. This is because they will now be grazing on pasture for their main diet, putting them at higher risk. However, there may be some cases where drenching is required before weaning under advice from your vet.
Subsequent drenching should be carried out at 28-day intervals if using oral drenches, or 42-day intervals if using injectable or pour-on drenches. Oral drenches have to be repeated more frequently as they have no persistence, so they only kill worms currently present in that animal. Whereas injectables and pour-ons have persistence, so they can kill worms that become present in that animal for a prolonged period after drenching.
The life cycle of a worm tends to be 21 days long. Waiting that extra week before drenching with an oral drench allows maintenance of your pasture’s refugia population, so that calves begin to develop immunity to adult worms.
These drenching intervals are key to ensure calves' exposure to worm burdens is gradual and controlled. In general, by 15 months old a good immunity should be established against worms if an effective drenching programme has been in place.
An example of a drench programme:
From weaning/November - March use an oral drench every 4 weeks.
From April - June (could continue this through winter if on grass) use an injectable drench every 6 weeks.
Thereafter in spring, summer and autumn (whenever needed – FEC testing recommended) use an injectable or pour-on.
Parasite types in our pastures
Worms and other parasite eggs and larvae live in the lower 2.5cm of grass and top 1cm of soil. They thrive in warm, wet conditions – which makes our southern farmland an ideal breeding ground for them.
Roundworms are some of the most prevalent worms in New Zealand, with two of the most common being cooperia and ostertagia. Cooperia are mostly a problem in young cattle, with calves becoming more immune around 12 months old. They find a home in the wall of the small intestine and can be resistance to mectin drenches. Ostertagia live in the lining of the forth stomach and tend to affect cattle under two years old. These worms can hibernate in stomach glands and often cause issues in youngstock coming out of winter. Most drench types will kill adult ostertagia worms, but mectin drenches will also kill larvae.
Another parasite that infects young calves is lungworm (dictyocaulus). Calves under 10 months old are most at risk. If pastures are highly contaminated it can be a bigger problem, but generally these worms are easily taken care of by most drenches.
There are three types of drench that target these sorts of parasites: mectins, clear and white. These different anthelmintic classes act differently and can target different types of worms. Often a brand of drench may contain more than one type to be even more effective. This is called a dual/double active or a triple active.
It’s also worth mentioning a separate type of parasite that can cause issues when raising calves, coccidia. We have seen quite a few cases of coccidiosis in calves this spring as some farms had to house them undercover for longer than normal due to the wet weather. These intense conditions allow coccidia parasites levels to build, and they will also be thriving in pastures where they can infect weaned calves.
Coccidiosis most commonly occurs in calves from 3-8 months old, but it’s occasionally seen in calves as young as four weeks old. It tends to present as a sudden onset of diarrhoea, which may contain blood and mucus. Impacts can vary from decreased growth rates right through to death. To confirm a diagnosis, we collect a faecal sample for testing and then treat affected calves with a coccidiostat. Some brands of drench include actives that defend against coccidia parasites.
Drench options available at VetSouth
We have several products available this season and our team can help guide you to the best choice for your calves. We recommend using oral drenches for youngstock for as long as practical, before switching to injectables or pour-ons.
Oral
Oral drenches are generally cheaper than other methods of drench and allow the most accurate dosage to be given to each calf. While using them can be quite labour intensive, they’re a reliable option for youngstock and can be safely given to calves once they weigh approximately 120kg – with some options even able to be given to 100kg calves.
Turbo Initial: Double active + anticoccidial – eprinomectin (mectin), levamisole (clear) and diclazuril (coccidiosis treatment). Dose rate 1ml per 10kg. Can be given to smaller calves from 100-120kg. Also contains cobalt and selenium to boost growth and immunity. Available in 1L, 2.5L and 5L.
Turbo Advance: Double active – eprinomectin (mectin) and levamisole (clear). Dose rate 1ml per 10kg. Can be given to smaller calves from 100-120kg. Also contains cobalt and selenium. Available in 5L.
Turbo Triple Minidose: Triple active – eprinomectin (mectin), levamisole (clear) and oxfendazole (white). Dose rate 1ml per 10kg. Also contains cobalt and selenium. Available in 1L, 5L and 20L.
Matrix-C: Triple active – abamectin (mectin), levamisole (clear) and oxfendazole (white). Dose rate 1ml per 20kg. Abamectin toxicity poses a risk to calves less than 120kg. Also contains cobalt and selenium. Available in 5L.
Corporal: Double active – levamisole (clear) and oxfendazole (white). Dose rate 1ml per 20kg. Available in 1L, 2.5L, 5L and 20L.
NEW DualForce: Double active – levamisole (clear) and oxfendazole (white). Dose rate 1ml per 10kg. Also contains cobalt, selenium, copper, iodine and zinc to support health and enhance growth. Available in 1L, 2.5L, 5L and 10L.
Injectable
Injectable drenches allow an accurate dose to be given in an easier way than orals. However, most of these drenches are aimed at calves weighing approximately 140kg and over, so they’re not recommended for a first drench.
Turbo injection: Double active – eprinomectin + ivermectin (co-mectin) and levamisole (clear). Dose rate 1ml per 50kg, a very low dose rate. Also treats sucking lice. Available in 500ml.
Eclipse E: Double active – eprinomectin (mectin) and levamisole (clear). Dose rate 1ml per 35kg. Available in 500ml.
Eclipse E with B12 & Selenium: Double active – eprinomectin (mectin) and levamisole (clear). Dose rate 1ml per 35kg. Also contains cobalt/B12 and selenium. Available in 500ml.
Pour-on
Pour-on drenches are the easiest to use, but are not the best option for younger calves as they’re not as accurate and can leave them at risk of ineffective coverage. So, it’s recommended to only begin using this method of drench once calves weigh approximately 150kg. The effectiveness of these drenches can also rely on the weather.
Turbo pour-on: Double active – eprinomectin (mectin) and levamisole (clear). Dose rate 1ml per 20kg. Available in 2.5L and 5L.
Eclipse pour-on: Double active – abamectin (mectin) and levamisole (clear). Dose rate 1ml per 20kg. Available in 2.5L, 5L and 5.5L.
Boss pour-on: Double active – abamectin (mectin) and levamisole (clear). Dose rate 1ml per 20kg. Available in 1L, 2.5L, 5L and 10L.
How can you help prevent drench resistant parasites?
Anthelmintic resistance is ability of parasites to survive treatment with a drench that has generally worked against them in the past. This resistance is inherited in a parasite population through genetics. Once established there is no reversing or reducing it. A rising global problem, this is now being seen in worms in New Zealand.
It’s good practice to conserve a proportion of worms in ‘refugia’ (not exposed to anthelmintic treatment – in refuge) on pasture or in untreated animals to dilute the progeny of resistant parasites that survive treatment. This is important for the maintenance of susceptible genes in the parasite population, which helps limit the development of resistance.
It’s also vital to follow guidelines and use drenches correctly to preserve the drenches that are still effective.
Drenching technique
Before drenching calves, weigh them individually and dose to the heaviest animal. If there is a large variation within the mob, then group them by similar weight and dose to the heaviest in each group. This ensures calves are given the right amount of drench to be effective and aren’t under dosed.
Check your drench guns are accurately dosing before starting and after every 200 doses.
Always read product labels before use to confirm details, particularly dose rates and withholding times.
Make sure the entire dose is received when using oral drenches.
Follow the correct drenching intervals depending on the type of drench.
Don’t mix drenches into milk. This can give variable dose rates and can also increase the rate of drench absorption, potentially resulting in toxicity.
Pasture management
After drenching calves, aim to return them to the same paddock they were on pre-drenching. Then move them to a new paddock roughly 3 days later. This allows any resistant worms remaining in the calves to be shed before moving on, reducing resistance selection pressure in the new pasture.
Try feeding silage to ease pressure on grass and reduce overgrazing if you have a limited number of paddocks suitable for calves. Parasite eggs and larvae tend to be in the last few centimetres of grass cover.
It’s a good idea to turn over the soil every few years and leave fallow over summer to desiccate larvae – particularly if you always use the same paddocks for calves. This will reduce the larval levels your calves are exposed to.
Testing for insights
We recommend FEC testing to discover what parasites you’re dealing with on your farm.
Faecal samples can be collected before drenching to confirm worm burdens, and then repeated after drenching to assess levels of resistance to different drench types.
We provide in-house FEC testing services across our clinics via Parasight machines. This can help us recommend the best drench to use for your situation.
Getting youngstock drenching right
Sticking to a programme and drenching on time, giving the full and correct dose of drench, and selecting an appropriate drench according to weight and parasite burden are vital during the first grazing season of young cattle.
Talk to the team at your nearest clinic for help choosing an appropriate drench. If you’d like further advice around any topics to do with parasite management, catch up with your KeyVet.
