Establish dosages, withholding periods and export slaughter intervals for all 37 parasiticides registered for use on goats

Summary

Compared to cattle and sheep, producers had fewer registered veterinary chemicals available to control parasites in goats. Goat producers were  also concerned that only a limited number of these may have effective dose rates or withholding periods (WHPs) and export slaughter intervals (ESIs) established for goats. 
The objective of this project was to investigate dosages, WHPs and ESIs for all parasiticides registered for use on goats in Australia and the extent to which these are supported by data, to promote efficacy and satisfy importing country residue limit requirements. This objective has been met. Of the thirty eight parasiticide products registered for use in goats, all have a WHP established for goats. WHPs are mandatory and must be included on the label of every registered product; therefore, all products registered for use in goats have a WHP established for goats. The 38 parasiticide products registered for use in goats in Australia represents only 14 actives. Australian MRLs have been established for all of these chemicals/drugs in goats and are published in the MRL standard on the APVMA website. Only one new parasiticide active (abamectin) has been registered for use in goats since the APVMA was given responsibility for establishing ESIs approximately 10 years ago. An ESI has been established for this product, based on a residues trial that demonstrated that abamectin residues declined to the level of quantification by 28 days after treatment. This is the only registered parasiticide product that has an ESI established for goats. 
To enable ESIs to be established for the other registered parasiticide products it is likely that similar studies will be required. This is because at least one important export market does not have an MRL established for the drugs/chemicals in these products. When important export markets have not established an MRL for a veterinary drug/chemical, the APVMA requires data showing tissue residue depletion to the level of quantification and does not accept extrapolation beyond sampling points when establishing an ESI. 
Generating these data was a costly undertaking and was unlikely to be a priority for the various product registrants because the actives are older compounds with generic competition and are also registered for use in cattle and/or sheep, with use in these species likely to be the major product uses. Review of the published veterinary literature revealed that for most of the actives for which published information was available, the label dose rate for goats was the same as that demonstrated as being effective in published efficacy studies. The exception was albendazole, for which it would appear the label dose rate may be lower than the ideal in terms of efficacy, particularly for the liver fluke Fasciola hepatica.