Journal of animal science2015; 93(4); 1824-1829; doi: 10.2527/jas.2014-8193

Quantification of sodium pentobarbital residues from equine mortality compost piles.

Abstract: Sodium pentobarbital, a euthanasia drug, can persist in animal carcasses following euthanasia and can cause secondary toxicosis to animals that consume the remains. This experiment was conducted to observe the effects of composting on euthanized horse carcass degradation and sodium pentobarbital residues in compost material up to 367 d. Six separate compost bins were constructed on pastureland. Three bins served as the control while 3 served as the treatment. The carbonaceous material, or bulking agent, consisted of hardwood chips mixed with yard waste wetted to approximately 50% moisture content. Bulking agent was added to each bin at a depth of 0.46 m, creating the pad. A licensed veterinarian provided 6 horse carcasses for use in the experiment. These horses had required euthanasia for health reasons. All horses were weighed and then sedated with an intravenous injection of 8 mL of xylazine. After sedation the 3 horses in the treatment group were euthanized by intravenous injection of 60 mL of sodium pentobarbital. The 3 control group horses were anesthetized by intravenous injection of 15 mL of ketamine hydrochloride and then humanely euthanized by precise gunshot to the temporal lobe. Following euthanasia, each carcass was placed on the center of the pad and surrounded with 0.6 m of additional bulking agent. Serum and liver samples were obtained immediately following death. Compost samples were obtained on d 7, 14, 28, 56, 84, 129, 233, and 367 while soil samples were obtained on d -1 and 367. Each sample was analyzed for sodium pentobarbital concentration. Compost pile and ambient temperatures were also recorded. Composting successfully degraded soft tissue with only large bones remaining. Data illustrate that sodium pentobarbital was detectable up to 367 d in compost piles with no clear trend of concentration reduction. Drug residues were detected in soil samples indicating that sodium pentobarbital leached from the carcass and through the pad. These findings confirm the persistence of sodium pentobarbital from equine mortality compost piles and emphasize the importance of proper carcass management of animals euthanized with a barbiturate to reduce environmental impact and secondary toxicosis.
Publication Date: 2015-05-29 PubMed ID: 26020203DOI: 10.2527/jas.2014-8193Google Scholar: Lookup
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  • Comparative Study
  • Journal Article


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The study observed the effects of composting on horse carcasses that were euthanized using sodium pentobarbital. It found that the drug persists for at least a year in compost piles, which highlights the importance of proper carcass management to mitigate environmental impact and avoid secondary toxicosis.

Objective of the Study

  • The aim of this research work was to examine the effects of composting on horse carcasses euthanized with sodium pentobarbital, a euthanasia drug.
  • The study focused on the degradation of the horse carcasses and the presence of sodium pentobarbital residues in compost material over a period of 367 days.


  • Six compost bins were built on pastureland. Three of these were used as controls and the other three were the experimental group.
  • The bulking agent used was a mixture of hardwood chips and yard waste moistened to about 50% moisture level.
  • Each bin had 0.46 meters of this bulking agent, which formed the composting pad.
  • A licensed veterinarian euthanized six horses with poor health using different methods: three horses were euthanized using sodium pentobarbital (experimental), and the other three were euthanized via a less toxic method (control).
  • The carcasses were placed in the center of the composting pads and covered with an additional 0.6 meters of bulking agent.
  • Samples of compost, serum, and liver were regularly taken in set intervals (from day 1 to day 367), and compost pile temperatures were also regularly monitored.


  • The composting process effectively degraded soft tissues, leaving mainly large bones intact.
  • Sodium pentobarbital was detected up to 367 days in the compost piles, with no evident pattern of concentration reduction.
  • The drug also leached into the soil, showing that the drug could move from the carcass through the composting pad.


  • The findings of this study underline the importance of proper carcass management protocols for animals euthanized with barbiturate drugs like sodium pentobarbital.
  • Improper carcass management could lead to the drug leaching into the environment, causing potential risks such as secondary toxicosis in animals that might consume the remains.

Cite This Article

Payne J, Farris R, Parker G, Bonhotal J, Schwarz M. (2015). Quantification of sodium pentobarbital residues from equine mortality compost piles. J Anim Sci, 93(4), 1824-1829.


ISSN: 1525-3163
NlmUniqueID: 8003002
Country: United States
Language: English
Volume: 93
Issue: 4
Pages: 1824-1829

Researcher Affiliations

Payne, J
    Farris, R
      Parker, G
        Bonhotal, J
          Schwarz, M

            MeSH Terms

            • Animals
            • Cadaver
            • Ecotoxicology / standards
            • Euthanasia, Animal / methods
            • Horses
            • Medical Waste Disposal / methods
            • Pentobarbital / analysis
            • Pentobarbital / toxicity
            • Random Allocation
            • Risk Factors
            • Soil / chemistry
            • Temperature


            This article has been cited 2 times.
            1. More S, Bicout D, Botner A, Butterworth A, Calistri P, Depner K, Edwards S, Garin-Bastuji B, Good M, Gortazar Schmidt C, Michel V, Miranda MA, Saxmose Nielsen S, Velarde A, Thulke HH, Sihvonen L, Spoolder H, Stegeman JA, Raj M, Willeberg P, Candiani D, Winckler C. Animal welfare aspects in respect of the slaughter or killing of pregnant livestock animals (cattle, pigs, sheep, goats, horses).. EFSA J 2017 May;15(5):e04782.
              doi: 10.2903/j.efsa.2017.4782pubmed: 32625488google scholar: lookup
            2. Shearer JK. Euthanasia of Cattle: Practical Considerations and Application.. Animals (Basel) 2018 Apr 17;8(4).
              doi: 10.3390/ani8040057pubmed: 29673140google scholar: lookup