Chemicals of concern in Australian beef cattle feedlot wastes – occurrence of ectoparasiticides and steroid hormones.
Conference contribution, 2012
Commercial feedlots for beef cattle finishing are potential sources of a range of trace chemical contaminants which have human health and environmental significance. The Meat and Livestock Association of Australia aim to ensure adequate protection of human and environmental health from exposure to these chemicals and have been working with the University of New South Wales to identify best practices for the management of contaminants in feedlot wastes. This involved studying the fate and analysis of key contaminants of concern in manure and composted waste on feedlot operations.
Chemical contaminants of concern identified include steroidal hormones - oestrogens (17β-oestradiol, 17α-oestradiol, oestrone) and androgens (testosterone, dihydrotestosterone, testosterone propionate, 17β-trenbolone, 17α-trenbolone) which are administered to beef cattle as hormone growth promoters. These compounds are of concern due to their endocrine disrupting properties.
Ectoparasiticides are also commonly used on Australian feedlots as anti-parasitic agents to control ticks, flies and lice. These include the synthetic pyrethroids (deltamethrin, cypermethrin, flumethrin) and macrocyclic lactones (ivermectin, doramectin, abamectin, eprinomectin). Good management of ectoparasiticides is important for the prevention of potential ecotoxicological implications, particularly towards dung beetles.
Very few of these chemical contaminants have been thoroughly investigated in terms of concentrations, effects and attenuation in feedlot wastes.
This project involved the development and optimisation of analytical methods to determine the fate and levels of these compounds in cattle manure and composted waste. These methods were applied to analyse feedlot samples taken after various stages of processing from Australian beef cattle feedlots. Synthetic pyrethroids were not detected in any of the samples while macrocyclic lactones and steroidal hormones were detected in some samples. These results will be discussed with respect to sample type, chemical usage, seasonal variation, waste management practice and ecotoxicological significance. The outcomes of this research aided in the development of best practice guidelines for the safe management of feedlot wastes in Australia.