Euthanasia Methods Research Articles

Intrahepatic Injection of Sodium Pentobarbital as an Alternative to Intraperitoneal Injection for the Euthanasia of Rats (Rattus norvegicus).

The most commonly accepted method of rat euthanasia in North America is intraperitoneal injection of sodium pentobarbital (PB). However, misinjection can occur, and intraperitoneal PB may cause pain and distress. The objective of this study was to test an alternative method of euthanasia: intrahepatic injection of PB. A pilot study was conducted to develop a method of intrahepatic injections (evaluated using CT scans and test injections), followed by a full study comparing intraperitoneal (n = 14) and intrahepatic PB injections (n = 66) in adult rats. Full study outcomes were: 1) time from injection to loss of right- ing reflex (LORR), 2) time from injection to cessation of heartbeat (CHB), 3) number of failed euthanasia attempts, and 4) confirmation of successful intrahepatic injection or misinjection via necropsy. All injections were performed by a veterinary student. CT revealed that intrahepatic injections were feasible. Times (median [range]) to LORR and CHB were faster after successful intrahepatic injections (LORR, 3 s [1 to 5 s]; CHB, 8 s [2 to 242 s]) than after intraperitoneal injections (LORR, 89.5 s [73 to 110 s], CHB: 284.5 s [237 to 423 s]). The misinjection rate was higher with intrahepatic injections (59%) than with intraperitoneal injections (29%), but intrahepatic misinjection still resulted in fast and successful euthanasia (LORR, 29 s [1 to 96 s]; CHB, 216 s [12 to 330 s]), with the injectate distributed between the intraperitoneal and intrahepatic locations. The number of failed euthanasia attempts with intrahepatic injections was low (n = 2). Intrahepatic injections show potential as an alternative to intraperitoneal injections for rat euthanasia.

Evaluation of Carbon Dioxide Euthanasia of Female Sprague Dawley Rats Alone or With Unfamiliar Conspecifics.

Most studies evaluating methods of euthanasia to date have focused on the euthanasia of individual animals. However, larger chambers are commonly used to euthanize multiple cages of animals at once. This study evaluated the use of a commercially available system for euthanasia of 1, 2, or 4 cages containing an individual female Sprague-Dawley rat using volume per minute displacement rates (VDR/min) of either 25% or 50% of 100% carbon dioxide. Animal wellbeing was assessed based on physiologic changes (serum noradrenaline and corticosterone) and behavioral assessments (relative frequency of rearing, line crossing, and grooming). The 25% VDR/min was associated with a significantly longer time to loss of consciousness, but this was not associated with significant physiologic or behavioral changes. The 50% VDR/min treatment group was associated with significant increases in the relative frequency of movement from 1 side of the cage to the other. Increases in the relative frequency of rears were detected in the 25% VDR/min treatment group when 2 or 4 rats were in the chamber as compared with a single rat in the chamber. The absence of significant physiologic changes suggest that the behavioral changes may have been associated with the novelty of the euthanasia experience rather than with distress. The location of the cage within the chamber did not significantly affect any of the measured parameters at either 25% or 50% VDR/min. These data suggest that groups of rats euthanized in these chambers are not experiencing decreases in their welfare.

Comparative Study of the Aftereffect of CO2 Inhalation or Tiletamine-Zolazepam-Xylazine Anesthesia on Laboratory Outbred Rats and Mice.

CO2 inhalation is currently the most common method of euthanasia for laboratory rats and mice, and it is often used for further terminal blood sampling for clinical biochemical assays. Lately, this method has been criticized due to animal welfare issues associated with some processes that develop after CO2 inhalation. The stress reaction and the value of the clinical laboratory parameters significantly depend on the used anesthetics, method, and the site of blood sampling. Especially in small rodents, an acute terminal state followed by a cascade of metabolic reactions that can affect the studied biochemical profile may develop and cause unnecessary suffering of animals. The aim of this study was to compare the stability of biochemical parameters of outbred Sprague Dawley rats and CD-1 mice serum collected after CO2 inhalation or the intramuscular injection of tiletamine–zolazepam–xylazine (TZX). The serum content of total protein and albumin, cholesterol, triglycerides, aspartate aminotransferase (AST), alanine aminotr ansferase (ALT), alkaline phosphatase (ALP), total bilirubin, and creatinine was decreased by the injection of TZX in comparison with CO2 inhalation. In addition, the levels of calcium, phosphates, chlorides and potassium were lowered by TZX vs. CO2 administration, while the level of sodium increased. Finally, the level of the majority of serum clinical biochemical parameters in rats and mice tend to be overestimated after CO2 inhalation, which may lead to masking the possible effect of anti-inflammatory drugs in animal tests. Injection anesthesia for small rodents with TZX is a more feasible method for terminal blood sampling, which also reduces the suffering of animals.

When and how to say goodbye: An analysis of Standard Operating Procedures that guide end-of-life decision-making for stranded cetaceans in Australasia

Standard Operating Procedures (SOPs) are tools used to ensure management best practice during emergency incidents including wildlife interventions, such as cetacean strandings. The compromised state of stranded cetaceans means humane end-of-life decisions may be considered, and SOPs frequently guide this process. This study evaluated SOPs for end-of-life decision-making and technically enacting euthanasia of stranded cetaceans across Australasia. The aim was to highlight similarities and differences in management and explore directions to improve stranded cetacean welfare. SOPs were requested from the eight government authorities across Australia and New Zealand. All SOPs were evaluated for decision-making criteria, yielding 29 parameters for the implementation of end-of-life decisions. Euthanasia and palliative care were options for end-of-life, with palliative care recommended when euthanasia was not feasible or presented human safety risks. Three euthanasia methods were recommended. Ballistics was recommended in seven SOPs, chemicals in five and explosives in three SOPs. Variability existed in the exact procedures and equipment recommended in all three methods. Additionally, only five SOPs provided criteria for verifying death, while only two recommended time-to-death be recorded, hindering evaluation of the welfare impacts of end-of-life decisions and euthanasia procedures. Our findings highlight the need for detailed guidance and consistency in end-of-life decisions and euthanasia techniques to ensure reliable welfare outcomes. Systematic, standardised data collection at euthanasia events across regions is required to facilitate assessment of welfare impacts and develop evidence-based recommendations. International collaboration is key to developing objective criteria necessary to ensure consistent guidance for end-of-life decisions.

An analysis of the approaches taken around the world to whale euthanasia

AbstractThe stranding of cetaceans raises significant welfare and associated logistical issues. A survey of opinions on euthanasia methods based on the recommendations of an International Whaling Commission (IWC) workshop was conducted. Descriptive statistics showed that the workshop recommendations were generally supported and understood, and these included the use of specific euthanasia techniques, but important barriers to adherence were identified, including lack of governmental support, lack of resources, and lack of experienced or trained personnel. Conjoint analysis of factors identified that ‘time to death’ was considered the most important determinant of welfare outcome. In view of the findings of this study, it is recommended that the IWC should consider creating a training programme for responders (both veterinary and non-veterinary) to ensure that trained personnel are available who can implement timely and tailored euthanasia techniques, if required, when strandings occur. Further research on this topic is also advocated to ensure a better understanding of what is being applied in different nations.

The choice of euthanasia techniques can affect experimental results in aquatic behavioural studies

With the use of animal models in research comes the responsibility of treating them ethically. While general anaesthetics are used to reduce pain, they have the potential to interfere with research results. This is a concern in behavioural ecology, particularly in aquatic systems where organisms use chemicals as a form of communication. One well-studied source of chemical information are alarm cues – compounds released from injured skin of conspecifics that mediate antipredator responses in nearby individuals and facilitate learned predator recognition when paired with novel predator cues. To determine whether chemical euthanasia interferes with the ecological functioning of alarm cues, we first exposed woodfrog tadpoles, Lithobates sylvaticus , to alarm cues prepared using different euthanasia, preparation and use methods (physical versus chemical euthanasia; mortar and pestle homogenization versus tissue homogenizer; cues used fresh versus frozen versus aged) and compared the intensity of their antipredator responses. Second, we exposed tadpoles to a novel predator odour paired with alarm cues obtained using either physical or chemical euthanasia techniques to elicit learning, and subsequently compared their learned responses. We found that tadpoles exposed to alarm cues prepared with a chemical euthanizing agent (MS222) displayed a weakened antipredator response that was not significantly different from our water (negative) control. Similarly, tadpoles were unable to learn novel predator odours as a threat when alarm cues were prepared with MS222. In contrast, alarm cues obtained using a physical euthanasia method yielded the highest responses regardless of preparation and use methods, with the exception of cues aged 24 h, which became nonfunctional. Our results confirmed the potential for chemical euthanasia methods to interfere with the functioning of ecologically relevant chemicals. Therefore, a single euthanasia method cannot be applied to all experimental situations – options are needed so researchers can select a method that provides adequate animal welfare without interfering with results. • Tadpoles exposed to MS222 prepared alarm cues had a weakened antipredator response. • Tadpoles were unable to learn novel odours as threats with MS222 prepared alarm cues. • Alarm cues remained effective after freezing but become ineffective if aged for 24 h. • Chemical euthanasia can interfere with ecologically relevant chemicals. • A single euthanasia method cannot be applied to all experimental situations.

Modification of a standard dump trailer into a mobile carbon dioxide depopulation unit for swine

Carbon dioxide (CO2) is an American Veterinary Medical Association approved swine euthanasia method. A limitation for the use of CO2 during depopulation events, such as a foreign animal disease diagnosis, is the ability to apply the method to finisher and adult pigs. The common euthanasia methods in finishing and adult swine require individual animal handling and restraint, increasing human safety risk in large-scale depopulation events. This project validates the modification of a standard dump trailer into a mobile CO2 depopulation unit. The success of the method was verified with subdermal implants for monitoring heart rate, activity, and body temperature.

The use of intrarenal injection of sodium pentobarbital for euthanasia in cats.

To determine whether intrarenal injection of sodium pentobarbital is a viable method for euthanasia in anesthetized client-owned cats and assess potential factors associated with time to cardiopulmonary arrest (TCPA) for such treated cats. 131 client-owned cats. In this retrospective study, client-owned cats presented for euthanasia between March 1, 2009, and January 15, 2010, were evaluated by veterinarians to determine suitability of intrarenal injection versus other methods of euthanasia. Cats included were anesthetized and then received 6 mL of sodium pentobarbital (390 mg/mL) by intrarenal injection. Results for TCPA were compared for cats grouped on the basis of variables of interest. 131 cats were included, of which 74 (79%) had a TCPA < 1 minute and 28 (21%) had a TCPA between 1.5 and 8 minutes after intrarenal injection. Most (124/131 [95%]) cats had no observable reaction to the intrarenal injection other than cardiopulmonary arrest. Median TCPA was longer for cats without (1 min; 25/131 [19%]) versus with (0 min; 106/131 [81%]) palpable kidney swelling upon injection. The effects of intrarenal injection of sodium pentobarbital in cats of the present study were similar to those typically observed with IV administration of euthanasia solution. When this intrarenal injection method is used, cardiopulmonary arrest with few agonal reactions can be expected to occur quickly in most patients. The intrarenal injection method is suited for euthanasia of anesthetized cats with easily located kidneys when IV access may be difficult.

Evaluation of Captive Bolt for Emergency Field Euthanasia in Canada Geese

ABSTRACTIn rare circumstances during research or monitoring operations for wild birds, emergency euthanasia is required. However, standard methods of euthanasia may not be humane for large birds. We evaluated the use of a Dick KTBG® spring‐powered, penetrating captive bolt for the euthanasia of Canada geese (Branta canadensis). We conducted trials on hunter‐harvested geese to determine anatomical placement of the device and to assess skull and brain penetration effectiveness. We then assessed the device for euthanasia on anesthetized geese. Although results using dead geese suggested the device may be effective (i.e., consistent skull penetration, and trajectory depth into relevant brain structures), we found the device did not produce consistent, humane euthanasia for anesthetized geese and was not suitable for emergency field euthanasia for Canada geese. We encourage further evaluations of emergency euthanasia methods using a 2‐step process of determining placement and efficacy on dead birds and then testing on live anesthetized individuals. © 2021 The Wildlife Society.

Screening of Anaesthetics in Adult Zebrafish (Danio rerio) for the Induction of Euthanasia by Overdose.

Simple SummaryAlthough zebrafish are used in vast numbers in laboratories all over the world, no consensus has been reached in the scientific community on a humane, consistent, and effective method for euthanasia of this species. Here, we screened commonly used anaesthetic drugs to see if an overdose could induce loss of reflexes of adult zebrafish in a rapid and reliable manner, and without causing distress. The tested anaesthetics were isoeugenol, clove oil, 2-phenoxyethanol, tricaine, benzocaine, lidocaine hydrochloride, and etomidate. We found that lidocaine hydrochloride, buffered with sodium bicarbonate and ethanol to increase its efficacy, induces loss of reflexes in a fast, predictable, and relatively peaceful manner. We recommend its use for adult zebrafish euthanasia.Zebrafish are often euthanized by overdose of anaesthesia. However, fish may have aversion towards some anaesthetics, and protocol efficacy varies between species. Using wild type adult Danio rerio, we assessed time to loss of opercular beat, righting, and startle reflexes during induction of anaesthetic overdose by either tricaine (0.5 g/L or 1 g/L), benzocaine (1 g/L), 2-phenoxyethanol (3 mL/L), clove oil (0.1%), isoeugenol (540 mg/L), lidocaine hydrochloride (1 g/L), or etomidate (50 mg/L). Initial screening demonstrated that benzocaine and buffered lidocaine hydrochloride achieved the fastest loss of reflexes. The rapid induction times were confirmed when retesting using larger batches of fish. The fastest induction was obtained with 1 g/L lidocaine hydrochloride buffered with 2 g/L NaHCO3, in which all adult zebrafish lost reflexes in less than 2 min. Next, we monitored signs of distress during benzocaine or buffered lidocaine hydrochloride overdose induction. The results indicated that buffered lidocaine hydrochloride caused significantly less aversive behaviors than benzocaine. Finally, we tested several buffers to refine the lidocaine hydrochloride immersion. The most efficient buffer for euthanasia induction using 1g/L lidocaine hydrochloride was 2 g/L NaHCO3 with 50 mL/L 96% ethanol, inducing immobility in less than 10 s and with only 2% of adult zebrafish displaying aversive behaviors during treatment.

Voluntary Oral Ingestion of a Sedative Prior to Euthanasia with CO2: Behavioural Responses of Mice.

Simple SummaryCarbon dioxide (CO2) inhalation is the most common euthanasia method for laboratory mice despite causing distress, pain and suffering. Since many laboratories will continue to use CO2 until a suitable alternative is identified, there is merit in exploring options for reducing its aversiveness. We evaluated the potential of using a voluntarily ingested sedative (tiletamine-zolazepam; Zoletil®) prior to euthanasia. Male and female C57BL/6 mice were offered cream cheese mixed with Zoletil® in one of the following doses: 0, 10, 20, 40, 80, or 100 mg/kg. Behaviour during the sedation and euthanasia periods was recorded. A dose of 20 mg/kg was found to achieve mild sedation and was likely to reduce the aversiveness of euthanasia with CO2. Higher doses also produced sedation, but these resulted in an incomplete intake of the dosed cream cheese in some mice. The voluntary ingestion of a sedative (20 mg/kg) prior to CO2 deployment could be a valid option for reducing the stress of this euthanasia method for both mice and staff. Additionally, we suggest that since mice readily ingested dosed cream cheese, this could also be an easy, effective, non-invasive, and low-cost means of reducing stress in other applications (e.g., repeated handling or sampling).Laboratory mice are commonly euthanised with carbon dioxide (CO2); however, there is ample evidence that this gas is aversive. Previous work suggests that sedation achieved via injection with benzodiazepines prior to CO2 administration could reduce aversive behaviours during euthanasia. We explored the potential of using a voluntarily ingested sedative (tiletamine-zolazepam, Zoletil®) prior to euthanasia. Male and female C57BL/6 mice were allocated into one of the five experimental groups, which differed in the dose of Zoletil: 0, 10, 20, 40, 80 or 100 mg/kg. A dose of 20 mg/kg was found to achieve mild sedation prior to euthanasia; mice which received this dose numerically reared and walked on the cage lid less, and showed ataxia, immobility and recumbency for longer than mice that received a lower dose. During euthanasia, mice that received 20 mg/kg showed fewer aversive responses to CO2. Doses of 40 to 100 mg/kg were associated with signs of moderate to severe sedation, but resulted in an incomplete intake of the sedative, which made the interpretation of the aversiveness to CO2 difficult. Voluntary oral administration of a sedative is an effective, affordable, and easy way to minimize the stress of mice to euthanasia with CO2.

USE OF TRICAINE METHANESULFONATE, CLOVE OIL AND 2-PHENOXYETHANOL FOR IMMERSION EUTHANASIA OF UNGA CICHLIDS (SAROTHERODON LINELLII).

Fish may warrant euthanasia for a variety of reasons, but euthanasia may be difficult to accomplish or confirm because fish can recover from deep anesthesia even after cardiac and respiratory arrest. The efficacies of three types of anesthetics were evaluated to compare their suitability for euthanasia of Unga cichlids (Sarotherodon linellii). Thirty cichlids were randomly assigned to be immersed in one of the three anesthetic solutions: tricaine methanesulfonate (MS-222), 2-phenoxyethanol (2-PE), and clove oil (CO) at doses of 1,000 mg/L, 2 mL/L, and 500 mg/L respectively. The opercular rates and caudal fin stroke rates were quantified, and the time to cessation of physiological measures (CPM) including caudal fin strokes, the reaction to external stimuli, the righting reflex, swimming, and operculation were recorded. Varying anesthetic induction times were observed with all three euthanasia solutions; the time to CPM in the 2-PE group occurred at a significantly slower rate than in the MS-222 group (P < 0.01). No significant differences were identified for the time to CPM when comparing the standard length or weight of the cichlids in all euthanasia solutions (P > 0.05). The cost of euthanasia per cichlid was calculated, with the most economically viable option being 2-PE; at more than seven times the price of 2-PE, MS-222 was the most expensive. After a 60-min immersion in the euthanasia solution, the presence of an audible heartbeat was identified in 100% of the cichlids immersed in 2-PE, 100% immersed in CO, and 90% in MS-222, indicating that they were not reliably euthanized. Therefore, a two-step protocol is recommended in cichlids for euthanasia: heavy anesthesia via immersion followed by an intravenous or intracardiac injection of euthanasia solution, or other secondary method of euthanasia.

Plasma oxidative stress in reproduction of two eusocial African mole-rat species, the naked mole-rat and the Damaraland mole-rat

One of the most prominent life-history trade-offs involves the cost of reproduction. Oxidative stress has been proposed to be involved in this trade-off and has been associated with reduced life span. There is currently an unclear relationship between oxidative cost and the reproduction-longevity trade-off. The current study, using a non-lethal and minimally invasive (only a single blood sample and no euthanasia) method, investigated whether an oxidative cost (oxidative stress) to reproduction would be apparent in two long-lived eusocial mole-rats, the naked mole-rat (NMR), Heterocephalus glaber, and the Damaraland mole-rat (DMR), Fukomys damarensis, where breeding colony members live longer than non-breeder conspecifics. We measured the direct redox balance in plasma by measuring the oxidative stress index (OSI) based on the ratio of total oxidant status and total antioxidant activity in breeders and non-breeders of both sexes, in the two species. NMR had significantly higher OSI between breeders and non-breeders of each sex, whereas DMR showed no significant differences except for total antioxidant capacity (TAC). The mode of reproductive suppression and the degree of reproductive investment in NMR may explain to some degree the redox balance difference between breeders and non-breeders. DMR show minimal physiological changes between breeders and non-breeders except for the mode of reproduction, which may explain some variations in TAC and TOS values, but similar OSI between breeders and non-breeders.

Use of potassium chloride for low-residue euthanasia of anesthetized California sea lions (Zalophus californianus) and northern elephant seals (Mirounga angustirostris) with life-threatening injury or disease.

To demonstrate the efficacy of potassium chloride (KCl) for low-residue euthanasia of anesthetized pinnipeds in field settings for which carcass retrieval for disposal is not feasible. Stranded, free-ranging California sea lions (CSLs; Zalophus californianus; n = 17) and northern elephant seals (NESs; Mirounga angustirostris; 6) with life-threatening injury or disease between May and August 2020. Each animal was anesthetized and then received a lethal dose of KCl solution administered by IV or intracardiac injection. The effective KCl dose; durations to cardiac arrest, respiratory arrest, and pupil dilation; and presence or absence of agonal breaths, muscle fasciculations, or skeletal movements were recorded. Mean effective dose of KCl was 207.4 mg/kg (94.3 mg/lb) for the 17 CSLs and 209.1 mg/kg (95.0 mg/lb) for 5 of 6 NESs (1 outlier NES was excluded). The range in duration from the beginning of KCl injection to cardiac arrest was 0 to 6 minutes, to pupil dilation was 0 to 5 minutes, and to respiratory arrest was 0 to 5 minutes. Muscle fasciculations, skeletal movements, and agonal breaths were observed in both species during and after KCl administration. The use of KCl provides an effective, low-residue method of euthanasia in anesthetized CSLs and NESs. Our recommended dose for these species is 250 mg KCl/kg (113.6 mg KCl/lb) delivered by intracardiac injection. Compared with euthanasia by barbiturate overdose, the use of KCl reduces the potential for secondary intoxication of scavengers and is appropriate in field scenarios in which the carcass cannot be retrieved for disposal.

Attitudes of laboratory animal professionals and researchers towards carbon dioxide euthanasia for rodents and perceived barriers to change.

Evidence indicates that carbon dioxide (CO2) induces negative affective states (including anxiety, fear and distress) in laboratory rodents, but many countries still accept it for euthanasia. Alternative methods (e.g. inhalant anaesthetic) may represent a refinement over CO2 but are not widely adopted. We conducted an online survey of Canadian and European laboratory animal professionals and researchers (n = 592) to assess their attitudes towards the use of CO2 and alternative methods for rodent euthanasia using quantitative 7-point scale (from 1 (= strongly oppose) to 7 (= strongly favour) and qualitative (open-ended text) responses. CO2 was identified as the most common method used to kill rodents, and attitudes towards this method were variable and on average ambivalent (mean ± SD score on our 7-point scale was 4.4 ± 1.46). Qualitative analysis revealed four themes relating to participant attitude: (a) the animal’s experience during gas exposure; (b) practical considerations for humans; (c) compromise between the animal’s experience and practical considerations; and (d) technical description of the procedure or policies. Many participants (51%) felt that there were alternatives available that could be considered an improvement over CO2, but perceived barriers to implementing these refinements. Qualitative analysis of these responses revealed five themes: (a) financial constraints; (b) institutional culture; (c) regulatory constraints; (d) research constraints; and (e) safety concerns. In conclusion, concerns regarding the use of CO2 often focused on the animal’s experience, but barriers to alternatives related to operational limitations. New research is now required on to how best to overcome these barriers.

Practical Euthanasia Method for Common Sea Stars (Asterias rubens) That Allows for High-Quality RNA Sampling.

Simple SummarySea stars are iconic marine invertebrates and are important for maintaining the biodiversity in their ecosystems. As humans, we interact with sea stars when they are used as research animals or displayed at public or private aquaria. Molecular research requires fresh tissues that have thus far been considered to be of the best quality if collected without euthanasia. This is the first paper describing a method to euthanize sea stars that still allows for sampling of high-quality tissue that can be used for advanced research. Since it can be difficult to tell if an invertebrate has died, it is important to use a two-step method where the first step makes it non-responsive and the next step ensures it has died. Sea stars were placed in a solution of magnesium chloride until they no longer reacted to having their underside or oral surface tapped. Sea stars did not seemingly find the magnesium chloride solution unpleasant. After they were no longer reactive, the sea stars were immediately sampled. Tissue from their digestive glands was extracted and interpreted to be of adequate quality for molecular research techniques. This study promotes animal welfare while maintaining high-quality tissue sampling for molecular research.Sea stars in research are often lethally sampled without available methodology to render them insensible prior to sampling due to concerns over sufficient sample quality for applied molecular techniques. The objectives of this study were to describe an inexpensive and effective two-step euthanasia method for adult common sea stars (Asterias rubens) and to demonstrate that high-quality RNA samples for further use in downstream molecular analyses can be obtained from pyloric ceca of MgCl2-immersed sea stars. Adult common sea stars (n = 15) were immersed in a 75 g/L magnesium chloride solution until they were no longer reactive to having their oral surface tapped with forceps (mean: 4 min, range 2–7 min), left immersed for an additional minute, and then sampled with sharp scissors. RNA from pyloric ceca (n = 10) was isolated using a liquid–liquid method, then samples were treated with DNase and analyzed for evaluation of RNA integrity number (RIN) for assessment of the quantity and purity of intact RNA. Aversive reactions to magnesium chloride solution were not observed and no sea stars regained spontaneous movement or reacted to sampling. The calculated RIN ranged from 7.3–9.8, demonstrating that the combination of animal welfare via the use of anesthesia and sampling for advanced molecular techniques is possible using this low-cost technique.

Evaluation of Euthanasia Methods on Behavioral and Physiological Responses of Newly Hatched Male Layer Chicks

Simple SummaryYoung poultry that are malformed, fail to hatch, or are not economically viable must be humanely killed at the hatchery. Maceration is the predominant method used and is instantaneous and humane. However, it is possible that new methods may be developed which could improve animal welfare and reduce suffering. In this study, we used gases and a vacuum system to kill chicks by reducing available oxygen. We found that using carbon dioxide or the vacuum system resulted in better welfare, as compared to the nitrogen treatment.Newly hatched male layer chicks are considered as “by-products” in the egg industry and must be humanely euthanized at the hatchery. Instantaneous mechanical destruction (maceration) is the predominant euthanasia method applied in poultry hatcheries and is approved by the American Veterinary Medical Association (AVMA). However, maceration is not perceived by the public to be a humane means of euthanasia. The effects of alternative euthanasia methods, including carbon dioxide (CO2) or nitrogen (N2) inhalation, and a commercial negative pressure stunning system on behavioral and physiological responses of day-of-hatch male layer chicks, were evaluated in a field trial. Chick behaviors, including ataxia, loss of posture, convulsions, cessation of vocalization, and cessation of movement, were monitored. Serum hormones were assessed at the end of each of the alternative euthanasia treatments, including a control group allowed to breathe normal atmospheric air. The N2 method induced unconsciousness and death later than the CO2 and negative pressure methods, and increased serum corticosterone concentrations of neonatal chicks. Carbon dioxide inhalation increased serotonin concentrations as compared to controls, as well as the N2 and the negative pressure methods. The behavioral and physical responses observed in this study suggest that both CO2 inhalation and negative pressure stunning can be employed to humanely euthanize neonatal male layer chicks.

The efficacy of three on-farm euthanasia methods for broiler chickens throughout the production cycle

ABSTRACT 1. There is a need to humanely kill moribund or injured broiler birds on-farm with no reasonable chance of recovery. Two experiments evaluated the efficacy of three commercially applicable killing methods; manual cervical dislocation (CD), mechanical cervical dislocation with the Koechner Euthanising Device (KED) and a non-penetrative captive bolt device (Zephyr-EXL; ZEXL), at 7, 21 or 35 d of age, on their ability to induce insensibility (unconsciousness and loss of brain stem reflexes) and death. 2. Experiment one assessed the damage to the cranial-cervical region resulting from the methods applied to cadavers of cull birds (n = 180) by radiography and gross pathology observation. 3. Experiment two evaluated the latency to insensibility and death when cull broiler birds (n = 240) were killed by CD, KED or ZEXL, using behavioural and reflexive indicators. Insensibility and death were measured by the absence of pupillary light, palpebral blink and nictitating membrane reflexes and cessation of rhythmic breathing, cloacal winking and convulsions. Analysis of variance for the main effect of the method was performed to determine the differences. 4. In experiment one, only the Zephyr resulted in skull fractures. A higher number of vertebral fractures occurred with KED application compared to CD, at 21 and 35 d. 5. In experiment two, indicators of sensibility were absent earliest with the ZEXL (μ < 2 s); then,CD (μ = 28 s) and were longest with KED (μ = 47 s), at 21 and 35 d. Cloacal winking and convulsions ceased earlier after CD (88 s), compared to either KED (124 s) or Zephyr (118 s). Death after a single application occurred 100%, 100% and 98% of time for CD, KED and ZEXL, respectively. 6. Overall, all methods were efficacious at inducing insensibility and death. Insensibility occurred earliest with ZEXL, whilst death occurred earliest with CD. KED resulted in the longest time to insensibility and death.

Deathly Silent: Exploring the Global Lack of Data Relating to Stranded Cetacean Euthanasia.

Simple SummaryCetacean strandings are frequent in occurrence and are likely to become even more common globally because of the effects of escalating anthropogenic activities. Due to the compromised state of stranded animals, euthanasia is often recommended or required. However, current knowledge and implementation of euthanasia methods remain highly variable, with limited data on the practicalities and welfare impacts of procedures. This study sought to evaluate the available published data on cetacean euthanasia in order to highlight significant knowledge gaps and provide direction to improve the welfare of stranded cetaceans. Data from the peer-reviewed literature and published reports were analysed, and significant knowledge gaps highlighted. Two main euthanasia methods, chemical and ballistics, were reported, with few details provided on the specific application of these. Few data were available about time to death/insensibility, parameters commonly required to assess the welfare impacts of killing methods. Overall, the findings highlight the lack of available information on cetacean euthanasia and suggest avenues for future work to improve welfare through the use of appropriate methods and increased data collection.The compromised state of stranded cetaceans means that euthanasia is often required. However, current knowledge and implementation of euthanasia methods remain highly variable, with limited data on the practicalities and welfare impacts of procedures. This study evaluated the available published data on cetacean euthanasia, highlighting knowledge gaps and providing direction to improve stranded cetacean welfare. A total of 2147 peer-reviewed articles describing marine mammal euthanasia were examined. Of these 3.1% provided details on the method used, with 91% employing chemical methods. Two countries, the United Kingdom (UK) and New Zealand (NZ), provided euthanasia reports to the International Whaling Commission (IWC) between 2007 and 2020. Methods employed were reported for 78.3% and 100% of individual cetaceans euthanised in the UK and NZ, respectively. In the UK, chemical euthanasia was most common (52%), whilst in NZ only ballistics methods were used. Few data were available about time to death/insensibility (TTD); 0.5% of peer-reviewed articles provided TTD, whilst TTD was reported for 35% of individuals in the UK and for 98% in NZ. However, IWC reports lacked detail on how death/insensibility were assessed, with multiple individuals “presumed instantly” killed. Overall, the findings highlight the lack of available information on cetacean euthanasia, and suggest increased data collection and the application of appropriate methods to improve welfare.

PSI-4 Quantification of Cooling Effects on Basic Tissue Measurements and Exposed Cross-sectional Brain Area in Cadaver Heads from Market Pigs

Abstract The objective of this project was to determine the impact of cooling on the soft tissue thickness, cranial thickness, and cross-sectional brain area of cadaver heads from market pigs. Documenting the effect of cooling on tissue dimensions of swine heads is valuable and important for future investigations of physical stunning and euthanasia methods that use cadaver heads. Cadaver heads were sourced from market pigs stunned with CO2. After transport to the data collection location, a captive bolt shot was applied in the frontal position. Following captive bolt application, each head (n=36) underwent an UNCHILLED and CHILLED treatment. The UNCHILLED treatment involved images collected immediately after splitting the head along the bolt path and the CHILLED treatment involved images of the same heads after storage in a walk-in cooler for 24 h at 2–4°C. All measurements for each treatment were determined from images of the heads cut along the plane of the bolt path immediately prior to and immediately after the refrigeration treatment. Measurements were performed by two observers; across all measurements, mean interobserver percent coefficient of variation (%CV) was 11.3±0.6%. The soft tissue posterior to the bolt path was different (P=0.0120) between treatments (CHILLED: 6.4±0.2mm; UNCHILLED: 7.2±0.2mm). The soft tissue thickness anterior to the bolt path was different (P=0.0378) between treatments (CHILLED: 5.5±0.2mm; UNCHILLED: 6.1±0.2mm). There was not a significant difference (P=0.8659) in cranial thickness posterior to the bolt path (CHILLED: 18.1±0.6mm; UNCHILLED: 18.3±0.6mm), nor was there a significant difference (P=0.2593) in cranial thickness anterior to the bolt path between treatments (CHILLED: 16.2±0.6mm; UNCHILLED: 15.2±0.6mm). Cross-sectional brain area did not differ (P=0.0737) (CHILLED: 3633.4±44.1mm; UNCHILLED: 3519.9±44.1mm). A correction factor of 1.12 was determined from this study for cases where estimation of UNCHILLED soft tissue thickness from CHILLED soft tissue thickness is necessary.