Environmental Considerations for Cattle

Environmental contamination

Some chemicals can be particularly toxic to aquatic organisms, wildlife and some important ecological insects such as dung beetles when used without reading the manufacturers label. Do not allow chemicals to enter water runoff, for example into storm drains or drainage ditches that could enter dams, water courses or surface water. Avoid treating animals with sprays in windy weather as spray drift could cause safety risks and off-target effects. Be particularly careful when mixing concentrates and make sure all manufacturer label and safety directions are followed. Pour-ons and injectables also must be used according to the manufacturers label and directions.

Cleaning dips

At times dips may need to be pumped out. A bunded (watertight) area to contain the dip wash should be used. Preferably an area with growing pasture and where sunlight and soil bacteria will degrade the chemicals should be designated for this purpose. Ensure that the dip wash cannot enter watercourses, dams or ponds. Stock should not graze this area for at least 3 months unless a shorter or longer interval is indicated on the product label.

Old dip sites

Very old dip sites can sometimes have remaining residues of persistent chemicals such as arsenic and organochlorines that were used in the 1960s and earlier. These chemicals have been prohibited for animal use for many years. However, it is important to be aware of this risk, particularly before re-commissioning old dips. Livestock should not be given access to old dip sites, they should be fenced off. Seek advice if you are concerned.

Dung beetles

Dung beetles have significant beneficial effects in cattle pastures. By breaking down and burying dung pats they clear the pasture of dung accumulation, return nutrients to the plant root zone and reduce compaction. They also reduce parasite challenge to cattle by removing breeding areas for bush flies, biting midges, buffalo flies and worms.

• Dung beetles disrupt parasite life cycles that rely on dung (bush flies, biting midges, buffalo flies and worms).
• Are negatively affected by some parasite control chemicals (some MLs and SPs).
• Populations are especially vulnerable in spring during their early breeding season.
• Check the product label for risks to dung beetles.
• Treatment by injection, pour-on, oral and dipping has a greater risk of effect on dung beetles.
• Treating cattle with ear tags has the least effect on dung beetles, followed by dust bags and back rubbers.
• Ongoing and repeated use of dung beetle–active chemical treatments have the worst effect on dung beetle populations.
• Minimise treatments with high risk chemicals when dung beetles are most active (October to March in northern Australia).
• Apply chemicals strategically, and only when economic thresholds for parasites have been exceeded, to reduce the number of treatments required.
• It is critical to use the dose rates specified on the label when treating cattle.

Some chemicals applied to cattle to control internal and external parasites can negatively affect dung beetle populations. Effects can include death of adult beetles, eggs or larvae, reduced breeding capacity of adults and retarded growth of larvae. Heavy chemical use can also lead to local extinction of some dung beetle species. Populations are especially vulnerable in spring during their early breeding season. In some situations, there may also be a short-term indirect effect on the rate of earthworm colonisation of dung pats.

Not all chemical treatments affect dung beetles and whether or not tick, fly, lice and worm treatments are damaging to dung beetles is determined by a number of factors. Harmful effects can be avoided with careful choice and use of chemicals.

Factors determining effects of chemical treatments on dung beetles

Chemical type: The different chemical groups and chemical actives registered for application to cattle and their likely effects on dung beetles are listed in Table 1. The two main groups implicated in undesirable effects on dung beetle populations are synthetic pyrethroids (SPs) and macrocyclic lactones (MLs), although the effects of chemicals from other chemical groups, particularly some more recently registered products are less completely defined. In addition, there are marked differences in the degree to which the different types of MLs impact dung beetles and these are listed in order from highest to lowest in Table 1.

Where there is a risk of effects on dung beetles, this is usually listed on the product label.

Method of chemical application: The likely effect of a chemical treatment method is determined by the amount of chemical absorbed. Most chemical is absorbed from injection, pour-on or oral and dipping treatments, less from over-sprays, even less from dust bags, back rubbers and least from ear tags. However, this is also influenced by the type and concentration of the chemical used. Depending on the chemical contained, slow release capsules (only registered for sheep not cattle in Australia) can have severe effects against dung beetle populations because of their prolonged release of active compound.

Mode of excretion from the animal: Chemicals where a significant proportion of unaltered chemical or toxic breakdown products are excreted in dung represent the greatest hazard for dung beetles. Synthetic pyrethroids (SPs) and macrocyclic lactones (MLs) and some insect growth regulator compounds (IGRs) are excreted mainly in the dung whereas most organophosphate compounds (OPs) are excreted principally in the urine and therefore have less effect on dung beetles.

Frequency and timing of chemical application: The worst effects on dung beetles occur when there is ongoing and repeated use of dung beetle–active chemical treatments, or where there is extended release of chemicals such as with controlled release capsules. Repeated or long-term use of dung beetle active chemicals can have significant and persisting impacts on populations. Effects can lead to local extinction of some dung beetle species in severe instances.

In northern Australia, dung beetles are most active from October to March and most susceptible to the effects of chemicals during this time. Minimise treatments with high risk chemicals during this period.

Strategic applications, and application only when economic thresholds for parasites have been exceeded, can reduce the number of treatments required. Have a worm egg count done and seek advice before treating for internal parasites; only treat cattle for ticks and buffalo fly once economic thresholds have been reached. Information on the effect of different chemical groups on dung beetles is provided on the chemical groups and actives pages.

Some animals are more susceptible to parasites and treating only the animals that really need treatment can reduce chemical use. For example, weaners and young cattle are most susceptible to worms; bulls usually carry the heaviest populations of buffalo flies. Bos indicus cattle are generally more resistant to parasites and require less treatment. Read the treatment sections in TickBoss, WormBoss, FlyBoss and LiceBoss for the best advice on when, what and how to treat cattle for the different parasite groups.

Concentration: It is critical to use the dose rates for parasite treatment products specified on the label. Even chemicals considered low risk to dung beetles can have damaging effects if used at higher than recommended dose rates. Beware that using lower than the label-recommended dose rates can also have undesirable impacts by leading to rapid resurgence in pest numbers, requiring more treatments, with ultimately greater effect on dung beetles.

For more information on dung beetles refer to the Dung Beetles Australia website.