Survey of veterinarians who use pentobarbital for euthanasia suggests knowledge gaps regarding animal disposal

Warren Hess Division of Animal and Public Health, AVMA, Schaumburg, IL

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 DVM
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Nathaniel Kollias Animal Welfare Division, AVMA, Schaumburg, IL

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 DVM, MPH
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Laura Pikel Marketing and Communications Division, AVMA, Schaumburg, IL

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Cia Johnson Animal Welfare Division, AVMA, Schaumburg, IL

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Emily Cornwell FDA/Center for Veterinary Medicine, Office of Surveillance and Compliance, US FDA, Rockville, MD

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 DVM, PhD
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Gail Golab Public Policy Unit, AVMA, Schaumburg, IL

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Susan Bright-Ponte FDA/Center for Veterinary Medicine, Office of Surveillance and Compliance, US FDA, Rockville, MD

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Neal Bataller FDA/Center for Veterinary Medicine, Office of Surveillance and Compliance, US FDA, Rockville, MD

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Mike Murphy Division of Animal and Public Health, AVMA, Schaumburg, IL

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 DVM, JD, PhD

Abstract

OBJECTIVE

To assess (1) veterinarians’ knowledge and practices regarding disposal of euthanized animals, (2) the extent to which veterinarians communicate with their clients about potential risks of rendering pentobarbital-euthanized animals, and (3) the extent to which veterinarians communicate potential relay toxicosis and environmental risks of pentobarbital-euthanized animals to clients.

SAMPLE

A stratified random sample of AVMA members.

METHODS

Over a 3-week period in early 2021, 16,831 of the AVMA’s 99,500 members were surveyed, with 2,093 responses (a 12% response rate). Respondents were assigned to 1 of 3 categories on the basis of their answers: veterinarians euthanizing only food-producing species, veterinarians euthanizing only non–food-producing species, and veterinarians euthanizing both food-producing and non–food-producing species (ie, veterinarians euthanizing mixed species).

RESULTS

Veterinarians responding to this survey appeared to be aware of the major methods of animal disposal, and about 89% reported communicating the method of euthanasia with clients to help ensure appropriate animal disposal. However, the need for additional education on local, state, and federal laws and rendering, as well as on risks of relay toxicosis including wildlife predation and environmental impacts, was reported.

CLINICAL RELEVANCE

Survey results identified gaps in veterinarians’ knowledge regarding animal disposal following pentobarbital euthanasia. Further education on this topic may be beneficial, particularly for early- and midcareer veterinarians who euthanize non–food-producing species and for veterinarians who euthanize mixed species in urban and suburban communities.

Abstract

OBJECTIVE

To assess (1) veterinarians’ knowledge and practices regarding disposal of euthanized animals, (2) the extent to which veterinarians communicate with their clients about potential risks of rendering pentobarbital-euthanized animals, and (3) the extent to which veterinarians communicate potential relay toxicosis and environmental risks of pentobarbital-euthanized animals to clients.

SAMPLE

A stratified random sample of AVMA members.

METHODS

Over a 3-week period in early 2021, 16,831 of the AVMA’s 99,500 members were surveyed, with 2,093 responses (a 12% response rate). Respondents were assigned to 1 of 3 categories on the basis of their answers: veterinarians euthanizing only food-producing species, veterinarians euthanizing only non–food-producing species, and veterinarians euthanizing both food-producing and non–food-producing species (ie, veterinarians euthanizing mixed species).

RESULTS

Veterinarians responding to this survey appeared to be aware of the major methods of animal disposal, and about 89% reported communicating the method of euthanasia with clients to help ensure appropriate animal disposal. However, the need for additional education on local, state, and federal laws and rendering, as well as on risks of relay toxicosis including wildlife predation and environmental impacts, was reported.

CLINICAL RELEVANCE

Survey results identified gaps in veterinarians’ knowledge regarding animal disposal following pentobarbital euthanasia. Further education on this topic may be beneficial, particularly for early- and midcareer veterinarians who euthanize non–food-producing species and for veterinarians who euthanize mixed species in urban and suburban communities.

Introduction

Pentobarbital is a preferred euthanasia option for animals; however, it presents animal disposal challenges. The Chemical Abstracts Service number for pentobarbital is 57-33-0. The PubChem ID is 23676152, and the molecular formula is C11H17N2NaO3.

Several drugs containing pentobarbital are approved by the FDA, and some drugs containing pentobarbital are marketed without FDA approval. At this time, drugs containing pentobarbital sodium approved by the US FDA Center for Veterinary Medicine are pentobarbital sodium (Somnopentyl Injection, N 004-536), pentobarbital sodium and thiopental sodium (Combuthal Powder, N 010-346), pentobarbital sodium and phenytoin sodium (Beuthanasia-D Special, N 119-807; Euthasol, A 200-071; Euthanasia-III Solution, A 200-280; and Pentobarbital Sodium and Phenytoin Sodium, A 200-614), and chloral hydrate, magnesium sulfate, and pentobarbital (Chloropent, N 046-789). Drugs containing pentobarbital marketed without FDA Center for Veterinary Medicine approval are discussed in Compliance Policy Guide Sec. 650.100.1 Additional information may be obtained by searching pentobarbital at the advanced search option at AnimalDrugs@FDA and DailyMed.

Because pentobarbital must reach the CNS to cause death via cardiorespiratory arrest, it is widely distributed throughout the body at the time of death. Due to the rapid onset of death, it is not significantly metabolized prior to death and may remain in animal tissues. One study2 of composted remains of horses euthanized with pentobarbital detected it at 367 days after euthanasia. Pentobarbital also may persist through some animal disposal methods, such as rendering, causing animal food containing such rendered product to be adulterated and potentially unsafe,35 which may result in harm to animals.6 Animal food found to be contaminated with pentobarbital has resulted in regulatory warning letters issued by the FDA and recalls.69 Pentobarbital may also present environmental (buried or composted euthanized animals) and relay toxicosis (pentobarbital toxicosis of an animal that feeds on or is fed a euthanized animal) risks.1016 For example, a 2-year-old female spayed Australian Shepherd presented comatose 2 hours after ingesting an unknown substance on a beach 3 weeks after a stranded juvenile humpback whale had been euthanized, necropsied, and removed from that same beach.10 Pentobarbital and phenytoin were detected by gas chromatography/mass spectrometry from tissue found on the beach near where the dog walked and in a urine sample from the dog.10 A recent review12 reported 125 cases of relay toxicosis affecting 432 wild and companion animal species in the US, Canada, the UK, South Africa, New Zealand, Australia, Germany, and France. A veterinarian and rancher were each ordered to pay $10,000 for involuntarily killing 5 golden eagles and 2 bald eagles after the eagles fed on the pentobarbital-euthanized carcasses of 2 mules.15

Relatively little was known about veterinarians’ knowledge of these disposal risks or the degree to which these risks are communicated to clients.17 To address this knowledge gap, the AVMA surveyed its members on euthanasia and animal disposal knowledge and practices. This manuscript reports survey results related to animal disposal. The objectives reported here were to assess the following: (1) veterinarians’ knowledge and practices regarding disposal of euthanized animals, (2) the extent to which veterinarians communicate with their clients about potential risks of rendering pentobarbital-euthanized animals, and (3) the extent to which veterinarians communicate potential relay toxicosis and environmental risks of pentobarbital-euthanized animals to clients.

Methods

Sample

A quantitative survey of AVMA members was conducted to gauge practitioner understanding of euthanasia methods, decision-making considerations for choice of euthanasia method by species, and recommendations made, or not made, for disposal of the resulting remains. This manuscript describes results from the survey related to veterinarians’ knowledge and communication surrounding disposal. A separate manuscript will describe survey results related to veterinarians’ understanding and decision-making considerations for euthanasia.

AVMA members self identify as working with a particular species or species type exclusively or predominantly, working in mixed-species practice, or professional activities not associated with a particular species or species type. (Approximately 25% of AVMA members do not self-report the species with which they work. These AVMA members were not sampled for this survey.) Of those working exclusively with a particular species or species type, approximately 54% identify as working with companion animals, 4% with equids, and 2% with food-producing animals. Of those indicating a predominant species or species type, 7% identify as working with companion animals, 1% with equids, 4% with food-producing animals, and 3% with mixed animals.

For this survey, the AVMA sampled its member veterinarians on the basis of their identified species to learn about their approach to pentobarbital euthanasia and subsequent disposal by species. Because of the relatively small number of veterinarians self identifying as farmed avian (poultry and waterfowl), farmed camelid/cervid, fish, nonhuman primate, rodent (purpose bred for research), swine (including pot-bellied pigs), wildlife, and zoo animal practitioners, all of these AVMA member veterinarians were surveyed. In addition, a random sample of veterinarians self identifying as dog/cat, equid (horses, mules, and donkeys), small exotic (birds, pocket pets, and reptiles), bison/cattle (dairy and beef), or sheep/goat practitioners were also surveyed. The survey comprised 21 questions (Supplementary Material S1), including questions about the type of community (rural, wilderness, urban, or suburban), the veterinarian’s career stage (early, mid, or late), and US geographic region in which euthanasia is performed. Responses stratified by community, career stage, and US geographic region are described elsewhere (Supplementary Material S2). The survey was conducted under approval No. 0910-00697 from the Office of Management and Budget in compliance with the Paperwork Reduction Act.

Over a 3-week period in early 2021, the AVMA received 2,093 responses from 16,831 of its 99,500 members (a 12% response rate). This response rate is typical for AVMA emailed surveys. Veterinarians responding to the survey were able to report more than 1 species, thus totaling 6,617 species responses.

Statistical analysis

Species were categorized as food producing and non–food producing. Bison/cattle (beef and dairy), farmed avian (poultry and waterfowl), farmed camelids/cervids, food fish, sheep/goats, and swine (including pot-bellied pigs) were categorized as food-producing species. Dogs/cats, equids (horses, mules, and donkeys), nonhuman primates, ornamental fish, rodents (purpose bred for research), small exotics (birds, pocket pets, and reptiles), wildlife, and zoo animals were categorized as non–food-producing species (recognizing that some wildlife and other species may enter the food supply).

Respondents were assigned to 1 of the 3 following categories based on their answers to Question 1 (Supplementary Material S1): veterinarians working with only food-producing species, veterinarians working with only non–food-producing species, and veterinarians working with both food-producing and non–food-producing species (mixed species). Responses of veterinarians working with only food-producing species and those working with mixed species were statistically compared for each of the food-producing species, and responses of veterinarians working with only non–food-producing species and those working with mixed species were compared for each of the non–food-producing species. Statistical analyses were performed in SPSS Statistics (version 26; IBM Corp). Pairwise tests of equality of column proportions were analyzed using z tests, and comparison of column means using t tests was used for scale variables. Descriptive statistics, percent, counts, and means were calculated to show data distribution. Tests for normality were not run due to the binary categorical nature of the survey data. Statistically significant differences (P < .05) for these veterinary categories are reported by objective and question in the comparison sections. Analysis of responses by career stage and community appear elsewhere (Supplementary Material S2).

Results

Objective 1: veterinarians’ knowledge and practices regarding disposal of euthanized animals

Information for this objective primarily comes from responses to survey questions 6, 10, 11, and 12 (Supplementary Material S1).

Question 6 concerned the dosage of pentobarbital for euthanasia. The labeled dose of pentobarbital products currently on the market in the US is 1 mL/10 lb (1 mL/4.5 kg), with some products also listing a maximum volume for horses and other large animals of 100 mL. Veterinarians responding to the survey reported using a range of doses for pentobarbital (Table 1; Figure 1). Across all species, 56.5% of veterinarians reported using 1 mL/10 lb (1 mL/4.5 kg), 10.0% reported using < 1 mL/10 lb (1 mL/4.5 kg), and 38.9% reported using > 1 mL/10 lb (1 mL/4.5 kg).

Table 1

Veterinary responses of pentobarbital dosage when used for euthanasia. Veterinarians were given options of (1) 1 mL/10 lb, (2) < 1 mL/10 lb, and (3) > 1 mL/10 lb. Note veterinarians reported > 1 dosage, so percentages for a given species add up to > 100%.

Species N 1 mL/10 lb < 1 mL/10 lb > 1 mL/10 lb
Food-producing species
 Bison/cattle 371 59.8% 27.8% 20.5%
 Farmed avian 234 56.4% 6.8% 42.3%
 Farmed camelids/cervids 221 63.3% 11.3% 29.9%
 Food fish 4 75% 0% 25%
 Sheep/goats 517 68.3% 9.9% 26.3%
 Swine 391 64.5% 7.4% 33.0%
Non–food-producing species
 Dogs/cats 1,421 59.5% 2.1% 44.5%
 Equids 681 56.8% 21.6% 26.9%
 Nonhuman primates 197 61.4% 3.0% 42.1%
 Ornamental fish 83 49.4% 14.5% 43.4%
 Rodents 332 48.8% 12.3% 41.9%
 Small exotics 778 43.4% 10.3% 50.8%
 Wildlife 366 46.4% 8.7% 51.1%
 Zoo animals 135 53.3% 7.4% 51.1%
Total 5,731 56.5% 10.0% 38.9%
Figure 1
Figure 1

Veterinary responses of pentobarbital dosage used for euthanasia. Veterinarians were given options of 1 mL/10 lb (1 mL/4.5 kg; black bars), < 1 mL/10 lb (gray bars), or > 1 mL/10 lb (light gray bars).

Citation: Journal of the American Veterinary Medical Association 261, 11; 10.2460/javma.23.03.0161

Using a dose of pentobarbital > 1 mL/10 lb (1 mL/4.5 kg) was more frequently reported for euthanasia of swine by veterinarians euthanizing mixed species (34.2%) than those euthanizing only food-producing species (5.9%). Veterinarians euthanizing only non–food-producing species more frequently reported use of > 1 mL/10 lb (1 mL/4.5 kg) for euthanasia of dogs/cats (50.7%) than did those euthanizing mixed species (36.3%).

Question 10 concerned responsibility for appropriate animal disposal after pentobarbital euthanasia. The most frequently reported responsible party (client, veterinarian, facility [intended to be an entity separate from the client], or “depends on circumstances”) for disposal after pentobarbital euthanasia varied, but each responsible party was reported at least once for every species in the survey (Table 2).

Table 2

Responsibility for appropriate animal disposal after pentobarbital euthanasia reported by food-producing exclusive, non–food-producing exclusive, and mixed veterinarians. Veterinarians reported > 1 responsible party, so percentages for a given species add up to > 100%. Bolded values indicate a statistically greater frequency of veterinarians in that category (mixed or exclusive) reporting responsibility of a particular party in that species (P < .05).

Species Veterinarians euthanizing food or nonfood species exclusively Veterinarians euthanizing food and nonfood species
N Client Veterinarian Facility Depends on circumstances N Client Veterinarian Facility Depends on circumstances
Food-producing animals
 Bison/cattle 20 50.0% 5.0% 55.0% 30.0% 351 72.1% 8.5% 14.8% 29.1%
 Farmed avian 6 16.7% 0.0% 66.7% 16.7% 228 39.9% 30.7% 17.5% 51.3%
 Farmed camelids/cervids 11 36.4% 9.1% 63.6% 45.5% 210 70.0% 10.5% 11.0% 34.8%
 Food fish 0 N/A N/A N/A N/A 4 25.0% 50.0% 75.0% 50.0%
 Sheep/goats 18 38.9% 5.6% 50.0% 44.4% 499 54.9% 13.8% 20.0% 35.1%
 Swine 17 47.1% 11.8% 47.1% 41.2% 374 42.0% 15.2% 34.2% 32.9%
Non–food-producing animals
 Dogs/cats 802 33.9% 30.0% 34.4% 57.6% 619 38.6% 29.2% 21.3% 53.4%
 Equids 229 55.5% 12.2% 17.9% 40.6% 452 71.9% 10.4% 11.3% 28.5%
 Nonhuman primates 98 1.0% 15.3% 83.7% 13.3% 99 7.1% 28.3% 70.7% 13.1%
 Ornamental fish 42 11.9% 31.0% 47.6% 40.5% 41 34.1% 48.8% 24.4% 43.9%
 Rodents 143 6.3% 15.4% 70.6% 23.8% 189 17.5% 20.6% 60.3% 27.0%
 Small exotics 467 31.0% 29.6% 35.8% 55.0% 311 31.2% 33.8% 28.6% 51.4%
 Wildlife 194 6.2% 38.1% 54.6% 28.4% 172 18.0% 44.2% 39.0% 42.4%
 Zoo animals 67 6.0% 29.9% 76.1% 13.4% 68 25.0% 27.9% 54.4% 32.4%

Food-producing species—Food-producing species veterinarians more frequently reported that a facility takes responsibility for appropriate disposal of bison/cattle, farmed camelids/cervids, farmed avian, sheep, and goats than did veterinarians euthanizing mixed species. Veterinarians euthanizing mixed species more frequently reported that the client takes responsibility for appropriate disposal of bison/cattle and farmed camelids/cervids than did veterinarians only euthanizing food-producing species (Table 2).

Non–food-producing species—Non–food-producing species veterinarians more frequently reported that a facility takes responsibility for disposal of dogs, cats, equids, nonhuman primates, ornamental fish, small exotics, wildlife, and zoo animals and more frequently reported that it depends on the circumstances for disposal of equids than did veterinarians euthanizing mixed species. Veterinarians euthanizing mixed species more frequently reported it depends on the circumstances for disposal of wildlife and zoo animals; that the client takes responsibility for appropriate disposal of equids, nonhuman primates, ornamental fish, wildlife, and zoo animals; and that the veterinarian takes responsibility for appropriate disposal of nonhuman primates than did non–food-producing species veterinarians (Table 2).

Question 11 asked, “which of the following methods are you aware of for the disposal of remains following pentobarbital euthanasia?” (Select all that apply for each species.) Veterinarians were given options of (1) rendering, (2) burial, (3) incinerator, (4) biodigester, (5) composting, and (6) other. The terms “rendering,” “burial,” “incinerator,” “biodigester,” “composting,” and “other” were not specifically defined in the survey.

The USDA defines rendering as an off-site process that uses heat to convert animal carcasses into safe, pathogen-free feed protein and other valuable end products while reducing the negative effects of the carcasses on people and the environment.18 States may have regulations referring to or defining these methods. For example, the State of Washington defines rendering as “the practice of using heat to convert dead animal carcasses and animal by-products into marketable products, such as meat and bone meal for animal feed, human food additives, or cosmetics,” burial as “placing a carcass below the natural surface of the ground and completely covering it with soil,” incineration as “the controlled and monitored combustion of carcasses for the purposes of volume reduction and pathogen control as approved by the department of ecology or local air pollution control authorities,” and composting as “the aerobic decomposition of organic matter under controlled conditions.”19 This code does not include a definition of biodigestion, but digestion is listed as an acceptable method for routine disposal or carcasses.19 Overall, veterinarians reported having awareness of the various disposal options available for euthanized animals (Table 3).

Table 3

Veterinary awareness of different disposal methods reported by food-producing exclusive, non–food-producing exclusive, and mixed veterinarians. Note veterinarians may be aware of > 1 disposal method, so percentages for a given species add up to > 100%. Bolded values indicate a statistically greater frequency of veterinarians in that category (mixed or exclusive) reporting awareness of a particular method in that species (P < .05).

Species Veterinarians euthanizing food or nonfood species exclusively Veterinarians euthanizing food and nonfood species
N Rendering Burial Incinerator Biodigester Composting Other N Rendering Burial Incinerator Biodigester Composting Other
Food-producing animals
 Bison/cattle 20 40.0% 65.0% 80.0% 45.0% 45.0% 0.0% 351 29.6% 88.6% 67.2% 30.5% 46.7% 3.1%
 Farmed avian 6 16.7% 33.3% 66.7% 33.3% 16.7% 16.7% 228 12.3% 81.1% 89.9% 19.7% 30.7% 3.5%
 Farmed camelids/cervids 11 27.3% 54.5% 90.9% 45.5% 18.2% 0.0% 210 26.7% 93.3% 70.0% 25.7% 35.7% 4.3%
 Food fish 0 N/A N/A N/A N/A N/A N/A 4 0.0% 50.0% 75.0% 50.0% 25.0% 0.0%
 Sheep/goats 18 33.3% 61.1% 94.4% 50.0% 33.3% 5.6% 499 23.0% 82.2% 78.6% 28.7% 37.1% 2.8%
 Swine 17 23.5% 64.7% 94.1% 47.1% 41.2% 0.0% 374 21.1% 70.6% 83.2% 31.6% 33.2% 2.7%
Non–food-producing animals
 Dogs/cats 802 12.1% 87.3% 99.0% 17.7% 8.1% 4.0% 619 7.4% 86.1% 95.2% 20.8% 13.9% 5.0%
 Equids 229 50.7% 86.5% 78.6% 21.8% 29.3% 3.9% 452 27.2% 93.4% 71.9% 23.9% 32.5% 5.1%
 Nonhuman primates 98 8.2% 19.4% 93.9% 32.7% 3.1% 1.0% 99 5.1% 23.2% 98.0% 36.4% 7.1% 3.0%
 Ornamental fish 42 23.8% 66.7% 95.2% 26.2% 19.0% 0.0% 41 12.2% 68.3% 92.7% 14.6% 19.5% 4.9%
 Rodents 143 11.9% 30.8% 96.5% 26.6% 4.9% 4.2% 189 8.5% 42.3% 94.2% 37.0% 15.3% 2.6%
 Small exotics 467 9.9% 81.6% 98.1% 17.6% 7.7% 3.6% 311 8.7% 78.5% 94.9% 21.2% 12.9% 5.5%
 Wildlife 194 15.5% 64.9% 95.4% 19.6% 8.2% 3.6% 172 9.9% 69.2% 90.7% 20.9% 18.6% 4.7%
 Zoo animals 67 22.4% 62.7% 97.0% 25.4% 4.5% 3.0% 68 7.4% 72.1% 92.6% 26.5% 14.7% 0.0%

Food-producing species—Veterinarians euthanizing mixed species more frequently reported awareness of burial for disposal of bison/cattle, farmed avian, farmed camelids/cervids, and sheep/goats than did veterinarians euthanizing only food-producing species (Table 3).

Non–food-producing species—Non–food-producing species veterinarians more frequently reported awareness of rendering for disposal of dogs, cats, equids, and zoo animals and more frequently reported awareness of incineration for dogs, cats, and small exotics than did veterinarians euthanizing mixed species. Veterinarians euthanizing mixed species more frequently reported awareness of burial for equids and rodents, biodigester for rodents, and composting for dogs, cats, rodents, small exotics, wildlife, and zoo animals than did non–food-producing species veterinarians (Table 3).

Question 12 asked, “which of the following methods do you use or recommend for the disposal of remains following pentobarbital euthanasia for [insert species from Question 2]?” (Select all that apply for each species.) Only those options selected in Question 2 were shown. Veterinarians were given the options of (1) rendering, (2) burial, (3) incinerator, (4) biodigester, (5) composting, and (6) other.

Although rare, some veterinarians reported using or recommending rendering of pentobarbital-euthanized animals. This was reported by at least 1 respondent in all species groups included in the survey except food fish (Table 4).

Table 4

Veterinary recommendations of different disposal methods following pentobarbital euthanasia reported by food-producing exclusive, non–food-producing exclusive, and mixed veterinarians. Note veterinarians may recommend > 1 disposal method, so percentages for a given species may add up to > 100%. Bolded values indicate a statistically greater frequency of veterinarians in that category (mixed or exclusive) reporting awareness of a particular method in that species (P < .05).

Species Veterinarians euthanizing food or nonfood species exclusively Veterinarians euthanizing food and nonfood species
N Rendering Burial Incinerator Biodigester Composting Other N Rendering Burial Incinerator Biodigester Composting Other
Food-producing animals
 Bison/cattle 20 5.0% 65.0% 50.0% 10.0% 15.0% 0.0% 351 13.1% 77.8% 38.2% 10.0% 23.6%
 Farmed avian 6 0.0% 16.7% 83.3% 0.0% 0.0% 16.7% 228 3.9% 56.6% 86.0% 6.1% 14.5% 2.2%
 Farmed camelids/cervids 11 0.0% 45.5% 81.8% 27.3% 0.0% 0.0% 210 15.2% 80.5% 52.9% 10.5% 17.1% 1.9%
 Food fish 0 N/A N/A N/A N/A N/A N/A 4 0.0% 25.0% 75.0% 0.0% 25.0% 0.0%
 Sheep/goats 18 55.6% 72.2% 11.1% 5.6% 5.6% 55.6% 499 9.0% 68.5% 59.1% 10.0% 17.2% 1.6%
 Swine 17 52.9% 58.8% 5.9% 29.4% 0.0% 52.9% 374 9.4% 54.5% 71.1% 11.0% 15.2% 1.1%
Non–food-producing animals
 Dogs/cats 802 1.6% 46.3% 97.4% 4.0% 0.9% 1.2% 619 2.3% 65.1% 91.1% 6.0% 3.7% 1.9%
 Equids 229 27.9% 64.6% 58.5% 5.2% 13.1% 3.1% 452 14.4% 84.1% 47.8% 8.8% 13.3% 2.0%
 Nonhuman primates 98 1.0% 4.1% 87.8% 20.4% 0.0% 1.0% 99 2.0% 13.1% 94.9% 10.1% 1.0% 0.0%
 Ornamental fish 42 4.8% 16.7% 95.2% 2.4% 0.0% 0.0% 41 0.0% 46.3% 85.4% 4.9% 7.3% 4.9%
 Rodents 143 2.8% 10.5% 94.4% 13.3% 0.0% 2.8% 189 3.2% 27.0% 93.1% 10.1% 4.8% 0.5%
 Small exotics 467 1.9% 41.3% 97.4% 4.7% 1.1% 1.1% 311 1.6% 55.6% 93.2% 4.5% 4.2% 2.3%
 Wildlife 194 6.2% 22.7% 91.8% 5.2% 2.1% 1.5% 172 1.7% 43.6% 84.3% 7.0% 7.0% 2.9%
 Zoo animals 67 9.0% 28.4% 88.1% 10.4% 0.0% 1.5% 68 0.0% 47.1% 89.7% 8.8% 7.4% 0.0%

Food-producing species—Veterinarians euthanizing mixed species more frequently reported burial of farmed camelids/cervids euthanized with pentobarbital than did veterinarians only euthanizing food-producing species (Table 4).

Non–food-producing species—Non–food-producing species veterinarians more frequently reported rendering of equids and wildlife euthanized with pentobarbital; incineration of dogs/cats, equids, small exotics, and wildlife; and biodigestion of nonhuman primates than did veterinarians euthanizing mixed species. Veterinarians euthanizing mixed species more frequently reported burial for dogs, cats, equids, nonhuman primates, ornamental fish, rodents, small exotics, wildlife, and zoo animals euthanized with pentobarbital and composting for dogs, cats, small exotics, and wildlife than did veterinarians euthanizing only non–food-producing species (Table 4).

Objective 2: veterinarians’ client communications about rendering pentobarbital-euthanized animals

Responses to survey Question 15 provided information for this objective (Supplementary Material S1). Respondents had options of strongly disagree, disagree, neither agree nor disagree, agree, and strongly agree for this question.

a. The method of euthanasia is explained to my client to help ensure disposal of the animal is appropriate—Overall, 11% of all respondents disagreed or strongly disagreed with this statement and 74% agreed or strongly agreed. About 6%, 13%, and 9% of veterinarians euthanizing food-producing species, non–food-producing species, and mixed species, respectively, reported they disagreed or strongly disagreed with the statement. Both veterinarians euthanizing mixed species and veterinarians euthanizing non–food-producing species more frequently strongly disagreed.

b. I advise my clients on disposal based on euthanasia technique and species—Overall, 14% of all respondents disagreed or strongly disagreed with this statement and 70% agreed or strongly agreed. About 6%, 17%, and 10% of veterinarians euthanizing food-producing species, non–food-producing species, and mixed species, respectively, reported they disagreed or strongly disagreed.

c. I am familiar with local and state laws surrounding use of pentobarbital for euthanasia and subsequent animal disposal—Overall, 18% of all respondents disagreed or strongly disagreed and 63% agreed or strongly agreed. About 24%, 20%, and 14% of veterinarians euthanizing food-producing species, non–food-producing species, and mixed species, respectively, disagreed or strongly disagreed.

d. I am familiar with federal laws surrounding use of pentobarbital for euthanasia and subsequent animal disposal—Overall, 22% of respondents disagreed or strongly disagreed and 55% agreed or strongly agreed. About 24%, 25%, and 17% of veterinarians euthanizing food-producing species, non–food-producing species, and mixed species, respectively, disagreed or strongly disagreed.

Objective 3: client communication regarding relay toxicosis and environmental risks

Responses to survey Question 16 provided information for this objective (Supplementary Material S1). Respondents had options of never, sometimes, about half the time, most of the time, always, and “I don’t use pentobarbital” for this question.

a. Use of pentobarbital to euthanize animals is a concern for relay toxicosis to wildlife and other species—Overall, 46% of respondents reported never or sometimes communicating this concern to clients and 44% reported most of the time or always. About 15%, 62%, and 29% of veterinarians euthanizing food-producing species, non–food-producing species, and mixed species, respectively, reported never or sometimes. Veterinarians euthanizing only food-producing species more frequently reported “I don’t use pentobarbital” (60%) than did either veterinarians euthanizing only non–food-producing species (2%) or veterinarians euthanizing mixed species (3%).

b. Use of pentobarbital to euthanize animals raises a concern for rendering the animal remains—Overall, 51% of respondents responded never or sometimes communicating this concern to clients and 40% reported most of the time or always. About 14%, 70%, and 33% of veterinarians euthanizing food-producing species, non–food-producing species, and mixed species, respectively, responded never or sometimes. Veterinarians euthanizing only food-producing species more frequently reported “I don’t use pentobarbital” (60%) than did either veterinarians euthanizing only non–food-producing species (2%) or veterinarians euthanizing mixed species (4%). Veterinarians euthanizing mixed species more frequently reported “I don’t use pentobarbital” (4%) than did those euthanizing only non–food-producing species (2%).

c. Disposal methods available for animals euthanized with pentobarbital can contaminate the soil and/or water—Overall, 56% of respondents responded never or sometimes communicating this risk to clients and 35% reported most of the time or always. About 19%, 68%, and 42% of veterinarians euthanizing food-producing species, non–food-producing species, and mixed species, respectively, responded never or sometimes. Veterinarians euthanizing only food-producing species more frequently reported “I don’t use pentobarbital” (60%) than did veterinarians euthanizing only non–food-producing species (2%) or veterinarians euthanizing mixed species (3%).

Additional survey feedback

Question 18 indicated, “if you have experienced issues with disposal of animals euthanized with pentobarbital, please describe,” and Question 21 asked for additional comments (Supplementary Material S1). Question 21 on this survey was open-ended, in which respondents provided any additional thoughts or feedback on the survey, their experience with using pentobarbital, or both, as free-text comments. These comments are briefly summarized as relating to education, relay toxicosis and environmental considerations, communication, and rules and regulations.

Education—Respondents requested education, stating, “educating veterinarians and veterinary students of the dangers of pentobarbital to the environment is needed.” Also, information on federal, state, and local laws needs to be made available to national, state, and local veterinary medical associations. Another respondent indicated they “would like more formal training in alternative euthanasia methods. Plus, the community needs education in this too.”

Relay toxicosis and environmental contamination—Several veterinarians had not previously considered relay toxicosis or environmental contamination, stating, “I have never thought about how the burial of a cat or dog would affect the environment and would like to learn more.”

Client communication—Client communication was mentioned in many comments. One comment captured the sentiment, “informational material from the AVMA that can be printed and given to a client at the time of euthanasia would be helpful, because clients are not always in the necessary state of mind to receive spoken information at that moment but might be within a few hours after the event.” Other comments also supported the desire for a concise AVMA fact sheet that could be given to clients when explaining the risks associated with disposal of chemically euthanized animals.

Animal disposal rules and regulations—Veterinarians and clients appear to use local landfills for animal disposal, sometimes for large food-producing species. Some comments included the following:

For large animals there are no other available methods in the area other than burial or landfill disposal; when I was in private practice, we never discussed the implications of toxicity related to euthanasia solution (it has always been implied). Makes me wonder what the liability of veterinarians is to discuss and explain this with clients. I know a recent law was passed requiring a letter be embossed on the forehead of pets receiving pentobarbital. I need clarification on this. I haven’t euthanized a pet since this law was enacted.

Respondents requested more information about potential conflicts between local and federal regulations regarding landfill as an option for pentobarbital-euthanized animals. They also asked for information about potential liability, particularly when veterinarians euthanize with pentobarbital. Training on federal, state, and local laws relevant to the use of pentobarbital for euthanasia was requested.

Discussion

Discussion and targeted outreach suggestions are presented first by objective, then by content, timeline, stakeholder group, and potential delivery mechanism.

Veterinarians responding to this survey reported using a range of doses of pentobarbital for euthanasia and a range of facilities to dispose of pentobarbital-euthanized animals. Some veterinarians reported use of > 1 mL/10 lb (1 mL/4.5 kg) in food-producing and non–food-producing species, which could increase the risk of environmental or animal food contamination depending on the method of disposal. Veterinarians reported widespread knowledge of disposal options; however, undesirable disposal options were recommended in some responses. Specifically, some veterinarians reported rendering or recommending rendering pentobarbital-euthanized animals. Rendering pentobarbital-euthanized animals is not appropriate because pentobarbital-containing rendered products can cause animal food to be adulterated and harm other animals.

This diversity of responses suggests a need for outreach regarding animal disposal, particularly regarding appropriate use of pentobarbital in animals and rendering of pentobarbital-euthanized animals. While this survey focused on pentobarbital, we note that other drugs may be present in a euthanized animal and the fate of these drugs also should be taken into consideration when disposing of animals. For example, relay toxicosis due to diclofenac in livestock carcasses has resulted in significant population declines in South Asian Gyps spp vulture populations.20 Outreach and education efforts should also address the possibility of relay toxicosis due to nonbarbiturate drugs.

The survey asked veterinarians about their knowledge of and recommendations for disposal; it did not ask clients about their knowledge of disposal methods. Within a veterinarian-client-patient relationship, the client agrees to follow the recommendations of the veterinarian, so communication is vital to the relationship. Animal welfare issues, increased risk of relay toxicosis, environmental contamination, food adulteration, regulatory and liability issues, or a combination thereof can result if the client does not follow the veterinarian’s recommendations.

Recommended actions include producing an informational resource with supporting tools for veterinarians; this would include working with appropriate stakeholder groups to support its development and dissemination. The resource should summarize (a) state regulations for pentobarbital possession and use, (b) appropriate animal disposal methods, and (c) federal regulations. Incorporating appropriate animal disposal options, categorized by euthanasia method, into Federal Emergency Management Agency, USDA, and State Animal Health Official training programs may also help improve compliance and reduce intrastate and interstate confusion. Readily available animal disposal information can foster understanding of potential safety issues, including relay toxicosis, environmental contamination, or contamination of rendered products.

Client communication about the method of euthanasia used is critical to ensure proper disposal. Although 89% of veterinarians reported explaining the method of euthanasia to their clients to help ensure appropriate animal disposal, some veterinarians in each category did not. Outreach to all veterinarians is indicated with an emphasis on veterinarians euthanizing mixed species and veterinarians euthanizing only non–food-producing species. Veterinarians frequently reported lack of awareness of local, state, and federal laws. Respondents increasingly disagreed or strongly disagreed with each successive statement in Question 15, indicating the importance of outreach increases accordingly for disposal method, impact of the euthanasia technique on disposal method, and applicable local, state, and federal laws. The AVMA’s existing animal disposal resource21 and veterinary compliance assistance animal disposal state resource locator22 may be sources of such information, while for California veterinarians, California’s infographic may be another.23

Client communication surrounding animal disposal following euthanasia, including rendering, relay toxicosis, and environmental risks, is critical to preventing adverse outcomes after disposal. Respondents indicated that communication with clients around relay toxicosis, food adulteration, and soil/water contamination does not occur in 45%, 51%, and 54% of cases, respectively. Veterinarians euthanizing only food-producing species reported more knowledge and communication of risks associated with animal disposal than did veterinarians euthanizing only non–food-producing species and veterinarians euthanizing mixed species. Veterinarians in rural/wilderness communities and late-career veterinarians reported more knowledge of these risks than those in urban or suburban communities and those earlier in their career (Supplementary Material S2). While each group of veterinarians may benefit from educational outreach regarding the issues addressed by Question 16, focusing on veterinarians working with non–food-producing species and veterinarians working with mixed species may be particularly beneficial based on these survey results.

Overall, our survey results suggest a desire for educational materials appropriate for both veterinarians and clients, as well as a need to further educate practicing veterinarians about risks associated with the use of pentobarbital and alternative methods of euthanasia. Respondent comments support the need to inform veterinarians about environmental risks associated with the use of pentobarbital, including appropriate animal disposal steps to be taken if the client assumes responsibility for disposal. Such training may reduce relay toxicosis, environmental contamination, and adulteration of animal food by encouraging veterinarians to either select other methods of euthanasia or clearly communicate proper animal disposal methods to clients following pentobarbital use. Respondents provided free-text comments indicating that education and resources (including handouts) are needed for effective client communication and information about local, state, and federal laws, particularly with respect to burial, composting, and rendering. Respondents also requested education on appropriate animal disposal, animal food adulteration, relay toxicosis, and environmental concerns.

Survey responses suggested potential avenues for outreach. Outreach needs to include appropriate stakeholders that can help provide access to and efficient dissemination of messaging over an appropriate timeline to ensure the knowledge gaps identified are promptly and effectively addressed.

An initial step was publication of a literature review17 that shared current scientific information regarding pentobarbital euthanasia and subsequent disposal with veterinary practitioners. Next, we propose targeted outreach to selected stakeholder groups. These groups will include species- and practice type–specific veterinary organizations, appropriate producer groups, animal food industry associations, drug sponsors, the State Animal Health Official, and state (eg, agriculture, fish and wildlife, pollution control, and public safety) and federal governmental agencies (eg, the FDA Center for Veterinary Medicine, USDA APHIS, USDA Food Safety and Inspection Service, Drug Enforcement Administration, and Environmental Protection Agency). Once these stakeholders understand the implications of this survey, it may be useful to establish working groups to identify the most appropriate means of developing and delivering consistent and targeted messaging for veterinarians and other stakeholders.

Examples might include presentations delivered in person at the AVMA Convention, the AVMA Humane Endings Symposium, and other appropriate veterinary conferences or on demand via AVMA Axon or USDA APHIS veterinary accreditation modules. In-person events may provide an opportunity to share concerns identified in the survey and solicit ideas for the most effective tools and educational resources to address them.

These survey results demonstrate important gaps in veterinarians’ knowledge of environmental, animal food adulteration, and legal risks associated with disposal of the remains of animals euthanized with pentobarbital. In general, better communication with clients regarding the method of euthanasia and appropriate animal disposal is indicated, particularly when pentobarbital is used. A substantial number of veterinarians responding to the survey indicated they needed informational handouts for their clients and further education for themselves, particularly around local, state, and federal regulations on pentobarbital use and animal remains disposal. All respondents to this survey were US veterinarians; however, pentobarbital intoxication of wildlife occurs in other countries as well. Therefore, educational outreach beyond the US could be beneficial.12 A multifaceted approach, with additional key stakeholder input, may be most effective and efficient for addressing knowledge gaps, advancing animal welfare, and mitigating risks of relay toxicosis, environmental contamination, and animal food adulteration.

Supplementary Materials

Supplementary materials are posted online at the journal website: avmajournals.avma.org

Acknowledgments

None reported.

Disclosures

The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.

Funding

This survey was supported by Contract No. 75F40120P00437 from the FDA to ICA Global, which then subcontracted to the AVMA.

References

  • Figure 1

    Veterinary responses of pentobarbital dosage used for euthanasia. Veterinarians were given options of 1 mL/10 lb (1 mL/4.5 kg; black bars), < 1 mL/10 lb (gray bars), or > 1 mL/10 lb (light gray bars).

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