Integrated Pest Management for the Horse Farm

12th October 2008

What the report is about

Horse owners are advised to ‘worm’ their horses every six to twelve weeks. Sole reliance on these chemicals to control horse parasites is expensive and most likely detrimental to horses, people and the environment. Resistance in worms to these chemicals is increasing. This leads to higher dosages administered more often. Administering chemicals to horses can be hazardous to both horses and handlers. This report looks at additional strategies that could be used to control worms in a more sustainable manner.

Who is the report targeted at?

This report represents a user friendly strategy targeted at recreational horse owners, stud managers, riding instruction establishments, equestrian clubs and environmental groups such as Landcare. Data from this report shows a need for further research on equine parasitology and pasture pest management.

Background

The dependence on insecticides to control pests in agriculture became very prevalent after the Second World War as new effective chemicals were developed. The ability to “clean up” pest problems in agriculture with chemicals such as DDT (Dichlorodiphenyltrichloroethane) was thought to be the answer to numerous pest problems. The development of resistance to chemicals, contamination of the environment and food products, and recognition of secondary pests has required a reduction in pesticide use and development of sustainable methods of pest control. The use of natural enemies is a main control component of alternative strategies. A prime goal of an Integrated Pest Management (IPM) program is to maximize the impact of these enemy organisms (van Emden 1982).

Aims/Objectives

This study aims to develop an alternative strategy to current equine parasite management that will aid and maintain environmentally sustainable horse farms. The lifecycle of horse parasites involves a ground dwelling stage that is vulnerable to native and exotic predators. The intention is to develop a biological control program that identifies native ground dwelling predators that can break the lifecycle of horse parasites. Predator lifecycles will be studied in relation to the effects of various horse wormers. Exotic dung beetles will also be established on horse farms to help aerate and fertilise pastures, increase water absorbency and reduce fecal run-off into farm and community water supplies.

The biological control program will:

• benefit the horse (less chemical administered)

• reduce financial costs of worming applications

• address chemical resistance

• lessen the risk of accidents to the horse handler

• maintain a more environmentally friendly and ecologically sustainable horse farm.

Methods used

The data presented in this report was obtained from ten horse farms which had different worming programs, ranging from drenching continually to drenching annually. The data was collected for two years from August 2004 – July 2006. The data collected from each trial site included studies of invertebrates from pitfall traps and invertebrates from dung.

Exotic dung beetles were commercially purchased and released at six sites. The winter active dung beetle Bubus bison was released in July 2004 at six sites and the summer active dung beetle Onthophagus binodis was released at the same six sites in November 2004. These beetles were not present before the releases. Although these beetles take years to establish it was evident that certain horse management practices would influence the establishment of the beetles such as continual use of ivermectin and encouraging bird activity in dung.

Fecal egg counts were taken by collecting fresh dung from the trial paddocks. Fecal egg counts were done monthly using the McMaster Technique (Bowman et al. 2003). Paddock management was recorded fortnightly for the number of horses, new horses, drenching time and chemical used per trial site. Management records showed that horse owners are rotating chemical brands and not actives when drenching.

Results/Key findings

There was no influence of chemicals used for drenching horses on ground dwelling invertebrates. Direct search of dung indicated that birds scattering the dung had a detrimental effect on the establishment of dung beetles. However, birds scattering dung caused the dung to desiccate, destroying the moist habitat that parasites require, leading to a reduction of parasite burden and quicker breakdown of the dung. Other invertebrates that live in dung had a composting effect, enabling faster breakdown of horse dung. Invertebrates in the dung were affected by drenching chemicals although bird activity was a significant variable. Seasonal gaps in beetle activity were evident enabling drenching chemicals to be used with a reduced risk of dung beetle mortality.

Exotic dung beetles were commercially purchased and released. Although beetles take years to establish it was evident that certain horse management practices were likely to negatively influence the establishment of the beetles such as continual use of ivermectin and encouraging bird activity in dung. Establishment of dung beetles, especially winter active beetles, should be encouraged on the horse farm.

Fecal egg counts were taken by collecting fresh dung from the trial paddocks. Resistance in worms to ivermectin was found for the first time in horses. Resistance should be a major concern for the horse owner.

Paddock management was recorded fortnightly in terms of the number of horses in a paddock, new horses introduced to a paddock, drenching time and chemical usage. Management records showed that horse owners are rotating chemical brands but not active constituents when drenching. This is a major concern for the development of resistance in worms especially with respect to resistance to ivermectin. Cultural practices such as harrowing, removal of dung and paddock rotation should prove to be a valuable component of horse parasite management.

Implications for relevant stakeholders

This project has highlighted limitations of current parasite control strategies in the horse industry. Parasitology should be a priority for further research as new technology and environmental direction is sought. Stud managers, recreational riders and other workers on horse farms would benefit from new technology as suggested in the recommendations. Workshops, media articles, talks and collaboration with community and Landcare groups represent channels to provide the industry with relevant information. There is a need for inexpensive fecal egg counts and commercial dung beetle supplies to ensure adoption of sustainable control strategies.

We have developed an IPM strategy that has the potential to:

• benefit the horse (less chemical administered)

• reduce financial costs of worming applications

• address chemical resistance.

The guidelines developed here should lead to more environmentally friendly and ecologically sustainable horse farms.

Recommendations

The following recommendations were made:

• Equine research in collaboration with bodies such as the dairy, beef industry and Landcare groups would benefit all stakeholders interested in control of pasture pests.

• Fecal egg counts are valuable for confirmation of strongyle (horse parasite) presence, however, it is not possible to separate eggs into large and small strongyles. Utilizing primers, a Polymerase Chain Reaction (PCR) approach has previously been developed for the specific amplification of ribosomal DNA, and hence identification of large and small strongyles. It would be useful if a PCR test became readily available to the horse industry along with cheap assessments of fecal egg counts.

• Additional research is needed to assess patterns of parasite mortality in paddocks. Rotating pastures for horses is a valuable component of parasite management.

• Data from this project shows significant peak flights of adult redheaded and blackheaded cockchafers. These adult beetles are attracted to light and research into light trapping could be useful components in controlling these pasture pests.

• The use of biological control of nematode parasites in livestock has been researched in cattle and horses in Europe with encouraging results. Nematophagous fungi would be a useful tool in sustainable biological control of parasites.

• The establishment of summer and winter active dung beetles is achievable with dung beetles already available in Australia. There is a gap in spring and autumn activity of exotic dung beetles in Australia. Appropriate exotic dung beetles are needed to reduce this gap for the horse and cattle industries.

The full article can be found at www.rirdc.gov.au/fullreports/index.html or purchased at ww.rirdc.gov.au/eshop