Controlling Roundworms in Beef Cattle Helps Protect Profits

A roundworm burden in beef cattle can lead to losses in productivity through reduced growth rates and reduced average daily live weight-gain (ADLWG). Controlling and treating roundworms therefore plays an important role in reducing the internal parasite burden, reducing production losses and improving profitability for cattle farmers.

Reductions in feed intake associated with parasitism can vary considerably over a range of -4% to -77%1. Indeed, research carried out in the U.S. has revealed major improvements to animal health and welfare as well as enhanced performance and productivity through the use of parasite control treatments2. Individual trials with beef cattle show the effect of anthelmintics on pregnancy rate range from an increase of 2.4 per cent3 to an increase of 120 percent4, the difference likely reflecting the specific nutritional, environmental and genetic conditions of the animals in the study. The de-wormer’s effect on the weaning weight ranged from an increase of nearly 0.3 per cent5 to over 13 per cent6. Prevention of parasites can therefore have a major impact the productivity of beef cattle.

Worms may impact significantly on performance without producing signs of clinical disease. Even subclinical parasitism, where only a few roundworms are present, can impact on productivity. Cattle may not only eat less but their feed efficiency can also be negatively impacted due to disruption of the digestive process. Nutritional resource gets allocated towards staging an immune response against the parasite challenge instead of growth and weight gain.

Grazing management practices will heavily influence exposure to roundworm larvae, while on-going preventative practices will minimise losses caused by clinical and sub-clinical parasite infections.

During the grazing season parasite control programmes should take into consideration the farm type, topography and facilities, so that the approach can be matched to the farm’s objectives and attitudes. Seasonality will inevitably impact on climate, plant growth, parasite epidemiology, cattle husbandry, farm management and housing, and thus parasite control. Parasite populations typically increase from mid-July onwards for parasitic gastroenteritis and lungworm infections are more common from July onwards. Map the farm at the start of the grazing season to determine the use of pastures, particularly in terms of parasite risk, when hay and silage aftermaths will become available, and which classes of stock will graze each pasture.

Each spring decide whether the parasite control plan will be strategic; adopting a planned approach to anthelmintic use, with whole-group treatments administered at specific risk periods, or whether a targeted approach to treatment, utilising a regular assessment of parasite risk to determine whether treatments are required is more appropriate.

For control of roundworm challenge in groups of youngstock to be effective, strategic anthelmintic treatments need to begin early in the grazing season. Thereafter, aim to minimise pasture contamination up to mid-July, by which time the over-wintered population should have declined to insignificant levels. If the approach is targeted, ensure that effective, regular monitoring such as weighing of cattle to assess growth performance is in place, to allow poorer performing individuals not meeting growth targets to be treated.

Close monitoring of pasture quality throughout the grass-growing season will allow farmers to cope with the unpredictability associated with grazing.

Set growth targets for young stock at grass, manage and feed accordingly and use anthelmintics alongside grazing management to ensure that parasite challenge does not prevent targets from being met. Growing cattle should be weighed regularly, as it is the only way to accurately monitor performance.

An effective, planned parasite control strategy can overcome the threat posed by all the major parasites of cattle. The appropriate use of anthelmintics can alleviate the effects of existing burdens and reduce the risk of subsequent disease.

Best practice is key; use parasite control products as recommended, using the correct applicator. Accurate dosing can only be achieved if animals are weighed before applying treatments, estimating liveweight by eye is inaccurate and can lead to over or under-dosing.

In order to get the best from parasite control products, farmers should:

  • Maintain all equipment and cattle handling facilities
  • Use the most appropriate product for the parasites present.
  • Administer products at the right dose.
  • Store and handle products safely and correctly.
  • Consult the label and/or datasheet before using a product.


  1. Forbes, A., 2008. Grazing behaviour, inappetence and production losses in cattle with sub-clinical parasitic gastroenterisits. Thesis. University Gent, Merelbeke.
  2. Larson, R. L., et al (1992). Effect of deworming with Ivomec on reproductive performance of yearling beef heifers. Kansas Agricultural Expermiment Station Research Reports, 0 (1), 53-55.
  3. Lawrence, J. D., and Ibarburu, M. A., (2007). Economic analysis of pharmaceutical technologies in modern beef production. Paper presented at the NCCC-134 Conference on Applied Commodity Price Analysis, Forecasting and Market Risk Management, Chicago, IL.
  4. Purvis, H. T., et al (1994). Weight gain and reproductive performance of spring-born beef heifer calves intraruminally administered oxfendazole. Journal of Animal Sciencce, 72 (4), 817-823.
  5. Stroh, T. L., et al (1999). Efficacy of spring time worming among beef cow calf pairs. Dakota: North Dakota State University.
  6. Stromberg, B. E., et al (1997). Production responses following strategic parasite control in a beef cow/calf herd. Veterinary Parasitology, 68, 315-322.

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1st April 2022

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