Abubakar, D.A., J.B. Adeyanju, and A.A. Tadros (2006). Laboratory animal euthanasia using intra-medullary injection of air. Sahel Medical Journal 9(1): 7-9. ISSN: 1118-8561.
Online: http://www.ajol.info/viewarticle.php?jid=73&id=26274&layout=abstract
Descriptors: animal welfare, euthanasia, small laboratory animals, medulla oblongata, rats, air injection, intramedullary.

Aldred, A.J., M.C. Cha, and K.A. Meckling Gill (2002). Determination of a humane endpoint in the L1210 model of murine leukemia. Contemporary Topics in Laboratory Animal Science 41(2): 24-27. ISSN: 1060-0558.
Descriptors: mice, experimental design, leukemia, animal models, animal welfare, posture, animal behavior, mortality, euthanasia, animal husbandry, animal use alternatives, animal use refinement, laboratory mammals.

Artwohl, J., P. Brown, B. Corning, and S. Stein (2006). Report of the ACLAM Task Force on Rodent Euthanasia. Journal of the American Association for Laboratory Animal Science 45(1): 98-105. ISSN: 1559-6109.
Abstract: The ACLAM Task Force on Rodent Euthanasia was appointed by President Lynn Anderson in 2002 in response to growing concerns and controversy regarding techniques that were commonly used for rodent euthanasia. Three issues were targeted as the focus of the report: euthanasia of fetal and neonatal rodents, the use of carbon dioxide for rodent euthanasia, and the impact of euthanasia techniques on data. The charge to the Task Force was to create a document that summarized in a scholarly and comprehensive manner all available data-based literature relevant to these topics, to assess the scientific merit of the design and conclusions of those studies, and to compile valid information into a concise and cohesive document that could serve as a resource for diplomates, other veterinarians, IACUC members, regulatory bodies, and research scientists. The Task Force has fulfilled this charge in an exemplary manner. During 2004-2005, the ACLAM officers and Board of Directors (BOD) reviewed and critiqued 2 draft versions of the report, and suggestions for change were incorporated into the document presented here. In July 2005, the BOD voted to forego the usual process of distributing the document to theACLAM membership for comment before release based on 2 considerations. First, the literature relevant to rodent euthanasia is continually expanding. As such, at each revision, the Task Force was compelled to incorporate new data and citations. Their consensus view was that new data would continue to emerge, and the document would require continual revision as the review process continued. Related to that, the 2nd consideration of the BOD was that information already accumulated would be of immediate utility to the stake-holders listed above. In lieu of a pre-publication comment period, the BOD and the Task Force instead invite all diplomates, as well as other parties, to comment via email or mail to the BOD liaison for this project, who will compile and maintain all remarks. After an interval deemed appropriate by the ACLAM President, a 2nd Task Force will be appointed to update and modify the Report. Comments will be considered at that time. I want to personally thank all members of the Task Force for their conscientious and comprehensive efforts in compiling this information. They have created a valuable and informative synthesis that should serve as a resource to the community for years to come.
Descriptors: laboratory animals, euthanasia methods, laboratory animal science, advisory committees, animal welfare, carbon dioxide toxicity, drug delivery systems, psychological stress, rodents.

Brooks, S.P.J., B.J. Lampi, and C.G. Bihun (1999). The influence of euthanasia methods on rat liver metabolism. Contemporary Topics in Laboratory Animal Science 38(6): 19-24. ISSN: 1060-0558.
Descriptors: euthanasia, rats, liver metabolism, influence, method, optimal method, impact on experimental data.

Conlee, K.M., M.L. Stephens, A.N. Rowan, and L.A. King (2005). Carbon dioxide for euthanasia: concerns regarding pain and distress, with special reference to mice and rats. Laboratory Animals 39(2): 137-161. ISSN: 0023-6772.
Abstract: Carbon dioxide (CO2) is the most commonly used agent for euthanasia of laboratory rodents, used on an estimated tens of millions of laboratory rodents per year worldwide, yet there is a growing body of evidence indicating that exposure to CO2 causes more than momentary pain and distress in these and other animals. We reviewed the available literature on the use of CO2 for euthanasia (as well as anaesthesia) and also informally canvassed laboratory animal personnel for their opinions regarding this topic. Our review addresses key issues such as CO2 flow rate and final concentration, presence of oxygen, and prefilled chambers (the animal is added to the chamber once a predetermined concentration and flow rate have been reached) versus gradual induction (the animal is put into an empty chamber and the gas agent(s) is gradually introduced at a fixed rate). Internationally, animal research standards specify that any procedure that would cause pain or distress in humans should be assumed to do so in non-human animals as well (Public Health Service 1986, US Department of Agriculture 1997, Organization for Economic Cooperation and Development 2000). European Union guidelines, however, specify a certain threshold of pain or distress, such as 'skilled insertion of a hypodermic needle', as the starting point at which regulation of the use of animals in experimental or other scientific procedures begins (Biotechnology Regulatory Atlas n.d.). There is clear evidence in the human literature that CO2 exposure is painful and distressful, while the non-human literature is equivocal. However, the fact that a number of studies do conclude that CO2 causes pain and distress in animals indicates a need for careful reconsideration of its use. Finally, this review offers recommendations for alternatives to the use of CO2 as a euthanasia agent.
Descriptors: animal welfare, laboratory animals, carbon dioxide, euthanasia methods, laboratory animal science, carbon dioxide, dose response relationship, mice, rats.

Danneman, P.J., S. Stein, and S.O. Walshaw (1997). Humane and practical implications of using carbon dioxide mixed with oxygen for anesthesia or euthanasia of rats. Laboratory Animal Science 47(4): 376-385. ISSN: 0023-6764.
NAL Call Number: 410.9 P94
Abstract: A series of studies was undertaken to determine whether CO2 can be used as a humane as well as practical agent for euthanasia or anesthesia of rats. Human volunteers rated the degree of discomfort associated with breathing 50 to 100% CO2 mixed with oxygen. Increasing concentrations of CO2 were judged as progressively more noxious, from "highly unpleasant" for 50% CO2 to "painful" for 100% CO2. The practical aspects of anesthesia and euthanasia with 50 to 100% CO2 were studied, using male Sprague Dawley rats. Time to anesthesia and death were inversely related to CO2 concentration, as were the frequency and severity of adverse reactions, including seizures and hemorrhaging from the nose. The severity of edema and hemorrhage, which were observed on histologic examination of the lungs of all rats euthanized with CO2, were greatest in the animals exposed to the lowest concentrations. There were no significant effects of CO2 concentration on time to recumbency or recovery, and there were no significant effects of precharging versus not precharging the chamber on any of the parameters studied. It was concluded that, although CO2 can be used in a humane manner, the concentrations that are least likely to cause pain and distress are associated with the longest times to anesthesia and death, highest incidence of unwanted side effects, and most severe histologic changes in the lungs. Acceptably humane and reasonably practical euthanasia or anesthesia can be achieved using a nonprecharged chamber and a low gas flow rate so that conscious animals are never exposed to CO2 concentrations >70%.
Descriptors: rats, laboratory animals, carbon dioxide, oxygen, anesthesia, euthanasia of animals, pain, animal welfare.

Fehr, M. (2002). Tierschutzgerechte Euthanasie bei Kaninchen, Meerschweinchen, kleinen Nagern und Reptilien. [Humane euthanasia of rabbits, rodents and reptiles]. Praktische Tierarzt 83(2): 128-135. ISSN: 0032-681X.
Descriptors: animal welfare, techniques, rabbits, reptiles, rodents, humane euthanasia.
Language of Text: German, Summary in English.

Fehr, M. (2002). Nyulak, tengerimalacok, kisragcsalok es hullok allatvedelmi kovetelmenyeknek megfelelo eutanaziaja. [Euthanasia of rabbits, guineapigs, rodents and reptiles, respecting animal welfare requirements]. Magyar Allatorvosok Lapja 124(5): 307-311. ISSN: 0025-004X.
Descriptors: animal welfare, euthanasia, guinea pigs, mice, rabbits, rats, reptiles.
Language of Text: Hungarian.

Gebhardt Henrich, S.G., K. Fischer, A.R. Hauzenberger, P. Keller, and A. Steiger (2007). The duration of capture and restraint during anesthesia and euthanasia influences glucocorticoid levels in male golden hamsters. Lab Animal 36(4): 41-46. ISSN: 0093-7355.
Descriptors: golden hamsters, glucocorticoids, animal stress, litter (bedding).

Gos, T., R. Hauser, and M. Krzyzanowski (2002). Regional distribution of glutamate in the central nervous system of rat terminated by carbon dioxide euthanasia. Laboratory Animals 36(2): 127-133. ISSN: 0023-6772.
Abstract: Carbon dioxide euthanasia is an established method for the termination of small laboratory animals. It has also been employed by the authors in neurobiological research on the postmortem glutamate concentration in the structures of rat brains. The following investigations were aimed at optimizing the termination procedure based on the CO2 saturation rate of the inhaled air. Two rates of CO2 flow were applied, and the higher one significantly augmented the glutamate level in the hippocampus and cerebellum. The relationship between this finding and signs of central fear reaction is discussed. The authors conclude that lower rather than higher CO2 flow in euthanasia procedures is gentler and is therefore preferable for use with laboratory animals.
Descriptors: rats, euthanasia, carbon dioxide, dosage, fearfulness, animal welfare, amygdala, hippocampus, cerebellum, glutamic acid, animal use refinement, fear reaction.

Grahwit, G. (2005). Toeten kleiner Nagetiere Anlaesse, Methoden and tierschutzgemaesse Bewertung. [Euthanasia of small rodents. Reasons, methods, and assessment of animal welfare]. Deutsche Tieraerztliche Wochenschrift 112(3): 95-97. ISSN: 0341-6593.
Descriptors: German Animal Welfare Act, euthanasia of vertebrates, available methods of euthanasia, small rodents, assessment of animal welfare, literature review.
Language of Text: German, Summary in English and German.

Hackbarth, H., N. Kuppers, and W. Bohnet (2000). Euthanasia of rats with carbon dioxide--animal welfare aspects. Laboratory Animals 34(1): 91-96. ISSN: 0023-6772.
Abstract: A method of inducing euthanasia by carbon dioxide (CO2) inhalation in the home cage of an animal is described and tested for distress by behavioural as well as by hormonal measures. The animals were maintained in their home cage while CO2 was induced at a flow of 6 l/min. The behaviour of the animals was measured continuously as were the serum concentrations of glucose, ACTH and corticosterone 30, 75 and 120 s after the CO2 was introduced into the cage. In order to test for distress, two groups of rats were pre-treated with acepromazine (orally) and pentobarbiturate (i.p. injection) respectively, in order to reduce possible distress caused by CO2 euthanasia, and were compared with control groups. There were no signs of distress by behavioural or by hormonal changes. All changes seen could be attributed to experimental effects and, especially as there was no difference between the pre-treated and the control groups of rats, it must be assumed that the described method of euthanasia is in concordance with animal welfare, it leads to rapid death without severe distress or pain, and it seems therefore to be 'humane'.
Descriptors: animal welfare, carbon dioxide, euthanasia, anesthesia, sedatives, animal behavior, rats.

Hayward, M. (2001). Disagrees with one aspect of the euthanasia panel report. Journal of the American Veterinary Medical Association 219(7): 907. ISSN: 0003-1488.
Descriptors: euthanasia, intraperitoneal injections, pain, rats.
Notes: Comment On: J Am Vet Med Assoc. 2001 Apr 15;218(8):1262.

Henke, J., C. Faltermeier, and W. Erhardt (2003). Anasthesie, Analgesie und Euthanasie bei kleinen Heimtieren. [Anaesthesia, analgesia and euthanasia of small pets]. Tierarztliche Praxis Ausgabe K, Kleintiere/Heimtiere 31(6): 394-397. ISSN: 1434-1239.
Descriptors: anesthesia, analgesia, euthanasia, inhaled anesthetics, injectable anesthetics, small animal practice, chinchillas, gerbils, guineapigs, hamsters, mice, rabbits, rats, veterinary medicine.
Language of Text: German.

Howell, R.L., C.L. Donegan, and C.A. Pinkert (2003). Mouse embryo yield and viability after euthanasia by CO2 inhalation or cervical dislocation. Comparative Medicine 53(5): 510-513. ISSN: 1532-0820.
Abstract: Efficient production of transgenic mice requires high yields of viable, healthy embryos. Cervical dislocation (without prior anesthesia) rather than CO2 inhalation as a means of euthanasia has been justified on the basis of the increased yield of viable ova, but controlled studies have not directly supported this contention. The American Veterinary Medical Association (AVMA) and Canadian Council on Animal Care (CCAC) Guides, and respective Institutional Animal Care and Use Committees (IACUC) have supported the use of CO2 as a preferred, humane method. The study reported here was undertaken to determine the relative yields of viable embryos from mice euthanized either by inhalation of 100% CO2 or by cervical dislocation. Inbred and hybrid mouse strains, representative of common strains used in genetic engineering experimentation included C57BL/6, FVB/N, and B6SJLF1. There was no difference in the embryo yields in comparisons using the two methods of euthanasia (P = 0.534). Decisions regarding the method of euthanasia can be made on the basis of criteria other than those associated with embryo yield and viability.
Descriptors: carbon dioxide, embryo physiology, euthanasia, spinal injuries, animal welfare, cell culture techniques, animal ethics, laboratory animal science, mice, inbred C57BL, trangenic mice.

Johnson, R. (2005). Evaluation of comparison between CO2O2 and CO2 gas in the euthanasia of mice. Animal Technology and Welfare 4(2): 117-119. ISSN: 0264-4754.
Descriptors: mice, euthanasia, CO2O2, CO2, comparison, animal welfare, stress.
Notes: Poster presentation originally presented at The Institute of Animal Technology Annual Congress, March 2005.

Kirkden, R.D., L. Niel, and D.M. Weary (2005). Aversion to carbon dioxide. Laboratory Animals 39(4): 453-455. ISSN: 0023-6772.
Descriptors: animal welfare, laboratory animals, carbon dioxide poisoning, euthanasia, rats.
Notes: Comment On: Lab Anim. 2005 Jul;39(3):353-4.

Klaunberg, B.A., J. O'malley, T. Clark, and J.A. Davis (2004). Euthanasia of mouse fetuses and neonates. Contemporary Topics in Laboratory Animal Science 43(5): 29-34. ISSN: 1060-0558.
Abstract: We sought to determine whether any of the common methods of euthanasia for adult rodents would lead to an acceptable death for fetuses or neonates. We wanted to identify a method that was rapid, free of signs of pain or distress, reliable, and minimally distressful to the person performing the procedure and that minimized the amount of handling required to perform the procedure. We evaluated six methods of euthanasia, with and without anesthesia, in three age groups of mice: gravid mice (E14-20) and neonatal pups (P1-P7 and P8-P14). Euthanasia methods included: halothane inhalation, carbon dioxide inhalation, intraperitoneal sodium pentobarbital, intravenous potassium chloride, and cervical dislocation with and without anesthesia. Noninvasive echocardiography was used to assess heartbeat during euthanasia. With cardiac arrest as the definition of death, no method of euthanasia killed fetal mice. Halothane inhalation (5% by vaporizer) was not an acceptable method of euthanasia for mice of the age groups tested. Intraperitoneal administration of sodium pentobarbital for euthanasia required a higher dose than the previously established dose, and there is a risk of reduced efficacy in pregnant animals due to potential intrauterine injection. Carbon dioxide asphyxiation was the most efficient method of euthanasia for neonatal mouse pups P1-14. For pregnant adult mice, intravenous potassium chloride under anesthesia, carbon dioxide asphyxiation, and cervical dislocation alone or under anesthesia were excellent methods of euthanasia. Copyright 2004 American Association for Laboratory Animal Science
Descriptors: laboratory animals, euthanasia, mice, newborn animals, carbon dioxide, echocardiography, halothane poisoning, chemically induced heart arrest, pentobarbital poisoning, potassium chloride poisoning, spinal injuries.

Kuppers, N. (1997). Beurteilung der CO2-Betabung von Laborratten auf Tierschutzgerechtigkeit. [Humane aspects of anaesthetizing laboratory rats with carbon dioxide]. Dissertation, Fachbereich Veterinarmedizin, Freie Universitat: Berlin, Germany.
Descriptors: laboratory animals, euthanasia, carbon dioxide, rats.
Language of Text: German, Summary in English.

Leach, M., M. Raj, and D. Morton (2005). Aversiveness of carbon dioxide. Laboratory Animals 39(4): 452-453. ISSN: 0023-6772.
Descriptors: animal welfare, carbon dioxide poisoning, euthanasia, animal methods, laboratory animals, rats.
Notes: Comment On: Lab Anim. 1999 Apr;33(2):155-61.

Leach, M.C., V.A. Bowell, T.F. Allan, and D.B. Morton (2002). Aversion to gaseous euthanasia agents in rats and mice. Comparative Medicine 52(3): 249-257. ISSN: 1532-0820.
Abstract: Despite euthanasia being the most common of all procedures carried out on laboratory animals, the potential distress associated with gaseous agents has received little interest until recently, with growing concern over use of carbon dioxide as a humane method of euthanasia. The distress associated with exposure to carbon dioxide, argon, and carbon dioxide-argon mixtures was investigated in rats and mice by measuring the degree of aversion on exposure to low, medium, and high concentrations of these agents. Animals were exposed to the various concentrations in a test chamber containing air or gas mixtures that they were able to enter and leave at will. Aversion was assessed, using measurements of initial withdrawal time and total dwelling time in the test chamber, as they were the most sensitive measurements of aversion. Comparisons between euthanasia agent and control (air) treatments indicated that concentrations of agents recommended for rapid and efficient induction are associated with some degree of aversion. Carbon dioxide and the carbon dioxide-argon mixtures were more aversive than was argon for rats and mice. These findings suggest that induction with carbon dioxide either alone or in combination with argon is likely to cause considerable distress before the loss of consciousness in rodents, which is unacceptable considering that effective and more humane alternatives are available.
Descriptors: rats, mice, euthanasia, hypoxia, carbon dioxide, argon, mixtures, animal welfare, distress, animal use refinement, escape responses, laboratory mammals.

Leach, M., V. Bowell, T. Allan, and D. Morton (2004). Measurement of aversion to determine humane methods of anaesthesia and euthanasia. Animal Welfare 13(Suppl.): S77-S86. ISSN: 0962-7286.
Descriptors: anesthesia, laboratory animals, rats, mice, carbon dioxide, halothane, general anesthetics, animal welfare, aversion, euthanasia.

McClure, D. and N. Anderson (2006). Rodents and small mammals. In: C.K. Baer (Editor), Guidelines for Euthanasia of Nondomestic Animals, American Association of Zoo Veterinarians: Lawrence, USA, p. 61-65. ISBN: 0-689-70726-6.
Descriptors: euthanasia, guidelines, inhaled anesthetics, potassium chloride, stunning, rabbits, rodents, CO2.
Notes: Available from AAZV.

McIntyre, A. and N. Lipman (2006). Controversy exists on the use of carbon dioxide (CO2) for the euthanasia of rodents. Journal of the American Association for Laboratory Animal Science JAALAS 45(4): 7. ISSN: 1559-6109.
Descriptors: laboratory animals, carbon dioxide toxicity, euthanasia, animal methods, rodents.

McIntyre, A.R., R.A. Drummond, E.R. Riedel, and N.S. Lipman (2007). Automated mouse euthanasia in an individually ventilated caging system: System development and assessment. Journal of the American Association for Laboratory Animal Science 46(2): 65-73. ISSN: 1559-6109.
Descriptors: mice, euthanasia, automation, animal housing, cages, ventilation systems, systems analysis, carbon dioxide, animal stress, distress.

Nemzek, J.A., H.Y. Xiao, A.E. Minard, G.L. Bolgos, and D.G. Remick (2004). Humane endpoints in shock research. Shock 21(1): 17-25. ISSN: 1073-2322.
Abstract: In biomedical research using animal models, the phrase "humane endpoints" refers to predetermined criteria used to judge when the research animals should be humanely euthanized. The intended goal of humane endpoints is to minimize the distress or suffering of research animals; however, if applied incorrectly, this well-intended concept could lead to premature decisions and inaccurate data, resulting in a waste of animal life. A concensus on specific endpoints for shock and inflammation research is not available but several biochemical, physical and behavioral parameters have been suggested for other research models. In addition, the authors have found, in the studies presented here, that increasing body weight, decreased body temperature, and inability to ambulate are important parameters in a model of cecal ligation and puncture. However, it is clear that the applicability of these endpoints may change with the model of disease, intensity of insults, experimental treatments and other factors. Consequently, humane endpoints should be assigned cautiously and preferably after preliminary studies to prevent aberrant research results. In order to accomplish this, investigators must become aware of certain concepts including: when to implement endpoints, what endpoints to consider, and how to establish the endpoints for their studies. Equipped with the basic principles of humane endpoints, investigators can make informed decisions that meet current standards of animal care while still achieving the scientific goals of their research studies.
Descriptors: research design, sepsis, shock, animal welfare, laboratory animals, body temperature, disease models, euthanasia, mice, rats, research.
Notes: Comment In: Shock. 2004 Aug;22(2):189; author reply 189-90.

Niel, L. and D.M. Weary (2006). Behavioural responses of rats to gradual-fill carbon dioxide euthanasia and reduced oxygen concentrations. Applied Animal Behaviour Science 100(3-4): 295-308. ISSN: 0168-1591.
Online: doi:10.1016/j.applanim.2005.12.001
Descriptors: rats, laboratory animals, euthanasia, carbon dioxide, argon, hypoxia, distress, physical activity, vocalization, escape behavior, animal well being.

Patrican, L.A. and R. Vaidyanathan (1996). Arthropod succession in rats euthanized with carbon dioxide and sodium pentobarbital. Journal of the New York Entomological Society 103(2): 197-207. ISSN: 0028-7199.
Descriptors: insects, habitat succession, euthanized mammalian carcasses, New York, decomposition of carcasses.

Pecaut, M.J., A.L. Smith, T.A. Jones, and D.S. Gridley (2000). Modification of immunologic and hematologic variables by method of CO2 euthanasia. Comparative Medicine 50(6): 595-602. ISSN: 1532-0820.
Abstract: Background and Purpose: The major goal was to determine whether variations in the method of CO2 euthanasia would induce significant immunologic differences. Methods: Young adult C57BL/6 mice (n = 40) were euthanized, using four regimens: 70% CO2/30% O2; 70% CO2/30% O2 leads to 100% CO2; 100% CO2-naive chamber; and 100% CO2 pre-charged chamber. Time to recumbency and euthanasia and body, liver, lung, spleen, and thymus masses were determined. Blood and spleen were further evaluated for leukocyte, lymphocyte, and thrombocyte counts, erythrocyte characteristics, distribution of lymphocyte subpopulations, spontaneous and mitogen-induced blastogenesis, complement activity, and cytokine production. Results: Time to euthanasia was five- to eightfold longer in mice exposed to 70% CO2/30% O2 than that for any other group. There were slight increases in mean erythrocyte volume (MCV) and mean erythrocyte hemoglobin (MCH) for all groups, compared with those for the 100% CO2 pre-charged group. Circulating cytotoxic T (CD8(+)) lymphocyte percentages and numbers, and spontaneous blastogenesis of leukocytes in blood and spleen, also were affected by euthanasia method. Conclusions: The method of CO2 euthanasia can result in significant differences in immunologic/hematologic variables. Thus, consistency in euthanasia procedures may be important in accurate interpretation of research data.
Descriptors: mice, euthanasia, carbon dioxide, mixtures, oxygen, lymphocytes, spleen, lymphocyte proliferation, blood serum, blood plasma, transforming growth factors, interleukin-2, tumor necrosis factor, experimental design, animal welfare, distress, hematologic tests, leukocyte count, complement activation.

Persinger, M.A. (2003). Rats' preferences for an analgesic compared to water: An alternative to "killing the rat so it does not suffer". Perceptual and Motor Skills 96(2): 674-680. ISSN: 0031-5125.
Abstract: A common policy in research institutions is to kill rats when they display chronic disabilities or recurrent injuries. These guidelines appear to be derived from an oxymoron that "it's better for a rat to be killed so it does not suffer pain" and from untested assumptions that rats cannot control "pain." In a two-bottle paradigm, 10 rats with a history of brain damage following status epilepticus from a single systemic injection of lithium and pilocarpine were given options to consume freely either tap water or 1 mg/cc of acetaminophen in tap water. During periods of fresh lesions due to persistent gnawing or acute injuries associated with tonic-clonic convulsions, the rats consumed 3 to 10 times the fluid from the bottles containing acetaminophen (equivalent to 5 to 10 extra-strength Tylenol tablets per day for a 70-kg person) relative to periods when no lesions or old lesions were present. These results suggest that rats with chronic injuries sufficient to be terminated according to Animal Care guidelines may be capable of reducing the aversive physiological conditions associated with tissue damage by selecting analgesic treatments.
Descriptors: analgesics administration and dosage, choice behavior, euthanasia, pain prevention and control, water, rats.
Notes: Comment In: Contemp Top Lab Anim Sci. 2003 Jul;42(4):7.

Pritchett, K., D. Corrow, J. Stockwell, and A. Smith (2005). Euthanasia of neonatal mice with carbon dioxide. Comparative Medicine 55(3): 275-281. ISSN: 1532-0820.
Abstract: Exposure to carbon dioxide (CO2) is the most prevalent method used to euthanize rodents in biomedical research. The purpose of this study was to determine the time of CO2 exposure required to euthanize neonatal mice (0 to 10 days old). Multiple groups of mice were exposed to 100% CO2 for time periods between 5 and 60 min. Mice were placed in room air for 10 or 20 min after CO2 exposure, to allow for the chance of recovery. If mice recovered at one time point, a longer exposure was examined. Inbred and outbred mice were compared. Results of the study indicated that time to death varied with the age of the animals and could be as long as 50 min on the day of birth and differed between inbred and outbred mice. Institutions euthanizing neonatal mice with CO2 may wish to adjust their CO2 exposure time periods according to the age of the mice and their genetic background.
Descriptors: inhalation anesthesia, animal welfare, carbon dioxide administration, euthanasia, age factors, newborn animals, mice, species specificity.

Sharp, J., T. Azar, and D. Lawson (2006). Comparison of carbon dioxide, argon, and nitrogen for inducing unconsciousness or euthanasia of rats. Journal of the American Association for Laboratory Animal Science 45(2): 21-25. ISSN: 1559-6109.
Abstract: We compared CO(2), Ar, and N(2) for inducing unconsciousness and euthanasia of Sprague-Dawley rats. We determined time to unconsciousness and monitored heart rate (HR) and mean arterial blood pressure (MAP) by radiotelemetry to assess stress, recovery after exposure, and time of death. Unconsciousness (mean +/- standard error) occurred 24 +/- 3, 87 +/- 8, and 93 +/- 8 s after short-term exposure to CO(2), Ar, and N(2), respectively. During exposure, CO(2) depressed HR, whereas Ar and N(2) increased HR. Upon removal from the chamber, rats' HR rapidly normalized after CO(2) or N(2) but remained elevated for 60 min after Ar. During exposure, all agents depressed MAP, which returned to resting levels 10 to 50 min after rats' removal from the chamber. For euthanasia, CO(2) at approximately 100% induced unconsciousness in 37 +/- 3 s, increased and then depressed MAP and HR, and caused death at 188 +/- 15 s. CO(2) at approximately 30% induced unconsciousness in 150 +/- 15 s, decreased HR and MAP, and induced death at 440 +/- 9 s. Ar at approximately 100% increased MAP but decreased HR, induced unconsciousness with hyperreflexia at 54 +/- 4 s, and caused death at 197 +/- 20 s. N(2) at approximately 100% decreased MAP but not HR and produced unconsciousness with hyperreflexia at 164 +/- 17 s and death at 426 +/- 28 s. We conclude that CO(2) effectively produced unconsciousness and euthanasia, but we were unable to ascertain distress. Ar also appears effective but produced hyperreflexia and tachycardia. N(2) was ineffective.
Descriptors: laboratory animals, argon, carbon dioxide, euthanasia methods, nitrogen, chemically induced unconsciousness, blood pressure, heart rate, Sprague Dawley rats, reflex, abnormal drug effects.

Smith, W. and S.B. Harrap (1997). Behavioural and cardiovascular responses of rats to euthanasia using carbon dioxide gas. Laboratory Animals 31(4): 337-346. ISSN: 0023-6772.
Descriptors: rats, behavior, animal welfare, carbon dioxide, destruction of animals, laboratory animals.

Stutler, S.A., E.W. Johnson, K.R. Still, D.J. Schaeffer, R.A. Hess, and D.P. Arfsten (2007). Effect of method of euthanasia on sperm motility of mature Sprague-Dawley rats. Journal of the American Association for Laboratory Animal Science JAALAS 46(2): 13-20. ISSN: 1559-6109.
Descriptors: rats, euthanasia, methodology, carbon dioxide, anesthetics, decapitation, spermatozoa, sperm motility, volatile anesthetics.

Wood, R.W. (2005). Aversiveness of carbon dioxide. Laboratory Animals 39(3): 353-354. ISSN: 0023-6772.
Descriptors: animal welfare, laboratory animals, carbon dioxide toxicity, escape reaction, euthanasia, research design, animal ethics, mice, rats, reproducibility of results.
Notes: Comment On: Comp Med. 2002 Jun;52(3):249-57.

Young, A. (2006). Halothane induction results in differing behaviours compared with Carbon Dioxide mixed with Oxygen when used as a rat euthanasia agent. Animal Technology and Welfare 5(2): 49-59. ISSN: 1742-0385.
Online: www.iat.org.uk
Descriptors: rat, euthanasia, halothane, oxygen-carbon dioxide mixture, delivery rates, discomfort.