Microsoft word - final avermectin advice note03-05-06 _3_.doc

Project Information Note
Date: 3rd May, 2006
For further information, contact Lisa Webb, Advisory Officer, RSPB Scotland
CONSERVATION CONSIDERATIONS REGARDING THE USE
OF AVERMECTIN ANIMAL HEALTH PRODUCTS
LISA WEBB, South and West Scotland Advisory Officer, RSPB Scotland
DAVY McCRACKEN, Senior Agricultural Ecologist, SAC
DAVE BEAUMONT, Senior Reserves Ecologist, RSPB Scotland
RUEDI NAGER, Senior Lecturer, University of Glasgow
This Project Information Note provides an overview of the findings from recently completed PhD research funded by RSPB Scotland and SAC and conducted jointly between SAC, University of Glasgow and RSPB. LIVESTOCK DUNG - A VALUABLE RESOURCE FOR FARMLAND WILDLIFE
Livestock dung supports a diverse community of
Although a number of species of dung insect are of invertebrates, as is illustrated by this figure which conservation interest in their own right, in general shows the number of individuals and range of the larger species (such as Aphodius dung beetle species within a small sample (approximately adults and larvae and yellow dung fly adults and 100 cm3) taken from a 2 month old cow pat in the larvae) are more widely known as being important food for a range of farmland birds and mammals. Many of these (such as rooks, chough, starlings, lapwings, wagtails, badgers, hedgehogs and shrews) obtain the insects by foraging directly within individual dung pats while others (such as swallows, martins and bats) take the insects in the air while flying over fields containing the dung 218 Adult
Beetles
Livestock dung can hold large numbers of insects, such as these adult Aphodius fimetarius dung beetles. THE EFFECTS OF AVERMECTINS ON INSECTS IN LIVESTOCK DUNG
Avermectins is the collective name given to the
adversely affect dung insects colonising individual active ingredients in a range of animal health dung pats (through either killing the adult insects products used to control internal worms and other or their larvae or impairing the adult insects ability parasites affecting farm livestock. After an animal to reproduce). This markedly reduces the number has been treated with an avermectin, residues of the and type of insects available to birds and mammals chemical are excreted from the animal in its dung. foraging within affected dung pats. Little was The highest residue concentrations occur in dung previously known about whether these effects at that is excreted in the first days after treatment, the level of the individual dung pat had any impact while smaller residue levels can be present in dung on the overall dung insect populations occurring at excreted up to several weeks after treatment. the field scale. This PhD research put a particular emphasis on investigating these latter aspects, The avermectin residues retain their insecticidal given concerns that any reduction in levels of dung properties in the livestock dung. It is well- insects in fields might limit the availability of insect documented that exposure to these residues can food for aerial foraging birds and bats. THE EFFECTS OF AVERMECTINS ON FIELD POPULATIONS OF DUNG INSECTS
This research focused on the abundance and
However, higher rates of physical abnormalities diversity of dung insects occurring within fields in were observed in adult yellow dung flies occurring Ayrshire grazed either by untreated cattle or cattle in the fields grazed by treated cattle. This may treated with doramectin (the active ingredient in reflect exposure to doramectin residues when those the products being used by the farmers on the flies were larvae developing in dung in those fields. study sites). Although differences in adult dung Additional experiments showed that several beetle and yellow dung fly populations were species of dung beetle avoided colonising dung evident both between different fields and within from doramectin-treated cattle when dung from individual fields over time, the results indicated untreated cattle was available. It is unclear whether that these differences and fluctuations in this was because beetles were repelled by the abundance and diversity were mainly due to residues or whether other factors reduced the weather and season. There was no evidence to attractiveness of the treated dung. This does, indicate that numbers of dung insects are however, suggest that it may be possible to reduce significantly reduced in fields grazed with beetle exposure to residues by ensuring that untreated dung is also available to colonise. Barn swallows collect dung-associated insects for their young when flying over Webb, L., McCracken, D., Beaumont, D. & Nager, R. (2006) Project Information Note: Conservation considerations regarding the use of avermectin animal health products. RSPB, Edinburgh, SAC, Edinburgh and University of Glasgow, Glasgow. CONSERVATION MANAGEMENT RECOMMENDATIONS
Dung insect populations are dependent upon dung being available to colonise. Hence, wherever there is a
conservation interest in dung insect populations (or in the birds and mammals which forage on such insects),
the first concern must to be to ensure that dung from grazing livestock continues to be available at the times of
year most appropriate to the species involved. This may therefore mean accepting the need to use livestock
which have been treated with avermectin products as part of a parasite control strategy.
• Where the conservation focus is particularly on • Where the conservation focus is particularly on aerial foragers (such as swallows, martins or species foraging within individual dung pats bats) then the results of this research suggest (such as lapwing, redshank and chough), then that there should be little concern over the there is still concern that a reduction in the insect resource within individual dung pats products (even if residues are present within could increase the time these species need to individual dung pats in individual fields spend foraging for food during key chick during the key dung insect foraging periods for growth periods. Ensuring that avermectin-free these aerial foraging species) provided that dung is also available to forage within may there is sufficient additional avermectin-free potentially limit any adverse impacts on dung available in and/or around the fields foraging vertebrates. Further research is, however, needed to investigate this fully. Irrespective of the specific conservation concerns, the overall objective should be to maximise the amount of avermectin-free dung which is available in and/or around a field at any one point in time during the spring and summer. The ways this could be achieved will depend on the individual situation, but could involve, for example, one or more of the following: • treating livestock only when necessary and avoiding treating older animals if they are not susceptible to the • grazing avermectin treated livestock in fields close to others containing untreated animals; • treating livestock with an appropriate non-avermectin product or moxidectin (a less toxic avermectin); • altering (if relevant from an animal health perspective) the timing of avermectin treatment in the spring (to change the period when residues in the pats coincide with key foraging periods of the vertebrates); • restricting the use of products containing doramectin, ivermectin or eprinomectin to housing of the livestock or in the autumn (when the main dung insect breeding season is over). Veterinary advice should, however, always be sought when designing or seeking to change a livestock parasite control regime. Dung from grazing livestock is essential for dung-associated insects and the birds and mammals which feed on these. Maintaining grazing regimes may involve accepting the need for a livestock parasite control strategy. RSPB Images. Webb, L., McCracken, D., Beaumont, D. & Nager, R. (2006) Project Information Note: Conservation considerations regarding the use of avermectin animal health products. RSPB, Edinburgh, SAC, Edinburgh and University of Glasgow, Glasgow.

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