Give your stock a clean start before winter housing
Eliminating parasites at housing will ensure optimum livestock performance over the winter. Niall Kerins, Teagasc Beef Specialist, discusses parasite treatment strategies for livestock during the winter housing period, focusing on the importance of proper product use and diagnostics.
Longer nights and shorter days. The All-Ireland finals long gone. Children back at school. Winter housing around the corner. We can’t do anything about the change of seasons, but you can give your animals a better chance to perform well over the winter with a parasite treatment plan.
Grazing is where cattle usually pick up internal parasites, including worms and fluke. Housing is when external parasites, like lice and mites, thrive. Treating animals with a parasite burden at housing can reduce the negative effects on health and performance, provided the product works effectively.
This year, especially given the mixed weather conditions over the past few months, there may well be a build-up of internal parasites that require treatment at housing. Effective treatment means cattle are virtually free of worms and liver fluke until they go back to grass. Careful planning prior to housing, and assessing the results of diagnostic tests taken during the grazing season, will help you to make informed decisions around dosing.
Faecal Egg Counts
The starting point for assessing internal parasites is completing faecal egg sampling from all categories of livestock. Faecal egg sampling can indicate the worm burden in livestock and also the presence of mature fluke.
Faecal egg samples can be relatively cheaply tested and analysed through your local vet or laboratory. The process of taking faecal egg samples is straightforward. Select 10-15 animals at random from a group of cattle. Put the animals in a clean concrete yard and allow them to stand there for one hour. Afterwards, collect a fresh faecal sample. Send it to be analysed promptly; delaying the process may result in the eggs hatching and giving an inaccurate result. Faecal samples that are being sent away for analysis should ideally be posted the day they are collected.
Results
Where possible, avoid completing the task on a Friday or over the weekend. This can mean samples are not tested immediately, which, again, can lead to incorrect results. Generally, results can take two to three weeks to be issued, so consider completing this task as soon as possible to have the test results available when selecting a dosing product.
The presence of worms in a faecal egg test is expressed in eggs per gram. Animals require a worm dose when the results show a count of greater than 250 eggs per gram. This outcome indicates a high prevalence of worms within the animal. As a result, the animal’s daily live weight gain will be compromised.
To determine if resistance to wormers is present on farms, some farmers have implemented a faecal egg reduction test or drench test. This involves collecting faecal egg samples from a batch of 10-15 animals before dosing, then applying the dose and retaking faecal samples 7 to 14 days later (7 days if a yellow product, 14 days if a white or clear product).
A reduction of 95% of eggs per gram in this test will indicate that the product is working effectively, while a <95% reduction suggests resistance to the product. Animals recently sent for slaughter usually receive a beef health check report along with the factory cheque. This report gives a score for liver fluke and is a reliable indicator of its presence on your farm.
Faecal sampling should be carried out regularly throughout the grazing period. However, faecal egg counts do not always reflect the presence of inhibited larvae of the stomach worm Ostertagia at housing. Consult your vet about the results prior to dosing. It is important to note that levamisole is not effective against inhibited larvae and is therefore not a good option for a housing dose.
Lungworm
Lungworm is a very common internal parasite that affects the lungs of an animal and can be problematic for all categories of livestock. Lungworms cannot be detected in a standard faecal egg test. If a large proportion of the herd is found to be coughing at grass, this can be an indicator of lungworm.
Lungworm usually becomes an issue during the second half of the grazing season and can remain a problem right through to housing. Pastures can become infected with larvae that stick to the grass sward. Grazing animals pick up larvae with grass, and, once digested, the larvae move from the gut into the lungs.
From there, the larvae produce eggs, which again hatch, and these larvae are passed through the animal in the dung. Sometimes eggs can be coughed up by the animal, and in warm, moist weather conditions, these eggs may hatch into larvae on grassland. The grazing pasture can become infected again with new larvae, and the cycle continues. Heavy lungworm burdens damage the lungs and airways of cattle. This damage, coupled with the stress around housing, can trigger the onset of respiratory disease.
Treatment for lungworms is widely available in the form of oral drenches, injectables, or pour-on products. The majority of products that treat lungworms will also treat gut worms/roundworms.
Fluke
Liver fluke infection has been shown to reduce the finishing weight of steers. Fluke requires the mud snail to complete its lifecycle, which is why wetter soil types or areas with high levels of rainfall favor the habitat of mud snails and can result in higher prevalence of fluke in cattle. Treatment needed for liver fluke varies from farm to farm. Some farms treat for fluke at housing every autumn due to past issues, while other farms might not have treated for fluke for many years.
With the wetter weather witnessed this year, and regardless of soil type, more farms may need to treat for liver fluke at housing. Faecal egg testing and reviewing beef health reports from animals slaughtered are the most effective steps to detect the presence of fluke in the herd. Liver flukes are classified as early immature (<6 weeks old), immature (6-12 weeks old), and mature (>12 weeks old). Be mindful that faecal samples only reflect the presence of mature liver fluke, so a negative sample does not always mean that an animal is free of fluke.
Several products are available to treat liver fluke. Triclabendazole is the only active ingredient available on the market to treat all stages of fluke, while other products may treat one or two stages of the liver fluke cycle. Resistance to triclabendazole has been documented in sheep, as it is the same fluke found in both cattle and sheep. This should be considered when choosing a dose. When using a product that does not kill all stages, it may be useful to delay treatment until after housing to allow all fluke present to mature so that the product is effective. Alternatively, a treatment can be given at housing with a repeat treatment 12 weeks later.
External Parasite Control
External parasites such as lice, mites, and other external pests can spread rapidly on livestock that are housed. External parasites typically spread between animals that are in close contact with each other, so at housing time, they can spread rapidly within a group. Hair loss and excessive scratching around gateposts are signs that external parasites are active. Products for treating external parasites are available in both injectable and pour-on forms.
The majority of pour-on products on the market will treat biting or sucking lice/mites on cattle but won’t treat for eggs. A large infestation may require a second treatment three to four weeks after the initial product was administered. Eggs on the animal’s back may hatch and cause a recurring issue. Treat all animals in the same group at the same time. If animals are added to the group, they too should be treated without delay.
Pour-on products require good skin contact for effective uptake. Clipping animals along their backs will ensure better uptake of the product. Additionally, clipping helps keep body temperatures cooler during mild weather.
Selecting a Product
There is no one product that can treat everything on your farm. Treating external or internal parasites may require administering two products at different times. Antimicrobial resistance is becoming a major issue on farms, mainly due to the incorrect use of products. This includes overusing certain products, using incorrect levels based on live weight, or using products unnecessarily. Recent weighing gives the best indication of how much product is required per animal.
Rotation
Consult with your vet on best practices for dosing products. Rotate different dosing products to prevent resistance from building up. Some products may have different names but contain the same active ingredient. Selecting a product with a different active ingredient will help prevent antimicrobial resistance. Only use combination products if necessary to target multiple parasites.
Products can have varying withdrawal times, so be conscious of this if using them on cattle intended for finishing. Of course, after getting a clean start at housing, the animals will almost certainly finish sooner.