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By Brad Hine Peter Hunt Tony Vuocolo Andrew Kotze Aaron Ingham 19 May 2021 4 min read

Livestock health, welfare and productivity are continually under threat from infections. In Australia alone, the estimated costs of some major diseases to the livestock industries in lost production and delivering control methods each year are $450m for nematodes in sheep, $180m for flystrike on sheep, $156m from cattle ticks, $100m from Buffalo fly on cattle and $45m from bovine respiratory disease in feedlot cattle.

Optimising the health and welfare of animals in their production systems is a high priority for livestock producers in Australia.

Therapeutic agrichemicals such as antibiotics, anthelmintics (antiparasitics) and insecticides are a necessary part of livestock production, but they can create issues as well.

For example, just like antibiotics in humans, resistance can render agrichemicals increasingly less effective over time in animals. It has also been theorised that antibiotic usage in animal production systems can in turn contribute to antibiotic resistance in human pathogens. There are also increasing concerns over environmental contamination from on-farm chemicals. For instance, arsenic and DDT residues have been found in soil, remnants from their historical use at dip stations.

For these reasons, the industry and our livestock health and resilience researchers are working on a variety of strategies and alternatives to help prevent and treat disease in Australian livestock and ensure their welfare is not compromised.

Vaccines, chemical preventatives, breeding disease resistant animals and clever management practices are a few such strategies we’ll touch on here.

CSIROs Dr Tony Vuocolo testing the flystrike vaccine

Clean, green vaccines

Vaccines are widely accepted as a clean and green approach to disease and parasite control and prevention. CSIRO has a long and proud history in livestock vaccine development. We developed the first commercial vaccine against an external parasite, cattle tick, and played a key role in developing the nematode vaccine, Barbervax. With our partners, we’re currently developing a vaccine against flystrike in sheep and are also looking at a scour worm vaccine. Vaccines will be important in contributing to the sustainability goal of significantly reducing agrichemical use in livestock production systems.

Improving agrichemical effectiveness

We’re developing diagnostic tests to identify parasite populations that are resistant to insecticides and anthelmintics, and the chemicals that remain effective against these parasite populations. We'll be able to advise livestock producers which agrichemicals will be effective on their property, and which ones they’re wasting their time and money using.

We’re also looking at identifying ‘resistance-breaking’ chemicals. Hopefully these will overcome drug resistance mechanisms in target parasite populations, hence helping restore the effectiveness of existing insecticides and anthelmintics. While these resistance-breaking chemicals themselves represent a synthetic chemical input into the environment, it might mean that livestock producers could avoid ever-increasing levels of chemicals to control parasites as they become more resistant.

Clever planning can reduce exposure of sensitive stock to disease and parasites

Targeted management to reduce exposure

Farmers can reduce costs and issues associated with agrichemical use by adopting an objective decision making process for treatment. Against internal parasites, for example, we have previously developed techniques for assessing whether select animals can be treated, rather than whole herds or flocks. More recently, we're developing modern DNA-based methods to detect worms. Best practice parasite control includes testing and treating for parasites only when there’s a health threat. Additionally, producers can test regularly for anthelmintic resistance to ensure they are only using anthelmintics that work.

Another targeted management technique is strategic planning to reduce exposure of sensitive stock to disease. This can mean using paddock rotations, in particular preparing paddocks with minimal parasite contamination where stock need to graze for lengthy periods, such as during calving or lambing. Same with ranges used by laying hens. Choosing calving or lambing time can also minimise exposure of sensitive lambs and calves to summer dominant parasites. We know now that immunity needs to be developed prior to exposure to seasonal disease threats and a strategic approach can build that into planned vaccination strategies.

More genetics, less antibiotics

Some animals (and humans!) have an enhanced natural ability to resist disease. By identifying these animals and using them in breeding programs, producers can improve the general disease resistance of animals in their production system.

Breeding for resistance to specific diseases has been practised successfully by the livestock industry for some time. However breeding for resistance to one disease can inadvertently increase susceptibility to another. We’ve developed methods to assess the capacity of an animal’s immune system to respond when challenged - termed immune competence. Rather than targeting resistance to a specific disease, this approach targets disease resistance in general and importantly, our methods are practical to apply on-farm.

Working with Angus Australia, we recently released a selection index, ImmuneDEX, which predicts the immune competence of Angus cattle. For the first time, Angus producers can use the index to select for improved health and fitness. Breeding livestock better able to resist disease should reduce antibiotic use on-farm in food producing animals, as well as improve animal health and welfare.

Alternatives to antibiotics

Immune stimulants are compounds that activate the immune system and can enhance its ability to cope with disease challenges. As such, these compounds are ideal candidates for use as alternatives to antibiotics to help prevent and treat disease in livestock. Unlike antibiotics, which are administered to the animal and act directly to neutralise pathogens, immune stimulants act indirectly by enhancing the ability of the animal’s own immune system. This mode of action means there is a reduced risk of pathogens developing resistance.

Just like humans, livestock undergo stressful periods in their life that can suppress their immune system and increase their risk of getting sick. Being weaned and separated from their mums for the first time is a prime example. We’re investigating whether immune stimulants administered just prior to stressful events like this can activate the immune system and provide rapid short-term protection against a broad range of diseases. Part of this is whether immune stimulants can enhance responses to vaccination when co-administered with various vaccines.

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