Quantification of sodium pentobarbital residues from equine mortality compost piles1

Preliminary research has shown that sodium pentobarbital (SP), a euthanasia drug, can persist up to 180 days in equine mortality compost piles. This study attempts to expand upon past research by quantifying SP residues in equine mortality compost piles over a longer duration using innovative sampling schemes. Six, 3.7 m 2 plots were used to construct separate compost bins with 3 bins serving as control. Each bin was constructed with 1.2 m high horse panels. The carbonaceous material consisted of wood chips that were added at a depth of 0.46 m creating the base. Twenty-four whiffle balls, pre-filled with wood chips were placed on the center of each pad. Nylon twine was tied to each ball for retrieval. Six horses requiring euthanasia for health reasons as determined by a licensed veterinarian were used for the study. The veterinarian supplied and humanely euthanized each horse. Each horse was sedated by injecting 8 ml of xylazine intravenously. Each of the three treatment horses were then euthanized by injecting 60 ml of SP intravenously. Each of the three control horses were anesthetized by injecting 15 ml of ketamine hydrochloride intravenously and then euthanized by gunshot to the temporal lobe. Immediately following euthanasia, each carcass was placed on the center of the woodchip pad and surrounded with 0.6 m of additional wood chips. Serum and liver samples were immediately obtained while whiffle ball, soil and compost samples were obtained over time. Each sample was analyzed for SP residues. Compost pile and ambient temperatures were also recorded. Preliminary data illustrates SP persistence up to 129 days in compost piles with no clear trend of reduction. Further sampling and analysis will be conducted.