Evaluation of a Commercially Available Euthanasia Solution as a Voluntarily Ingested Euthanasia Agent in Laboratory Mice.

All currently accepted methods of euthanasia for laboratory mice involve some degree of stress, fear, anxiety, or pain. We evaluated the voluntary oral administration of a euthanasia drug in 99 male and 81 female mice of various strains. We first explored the palatability of sugar-cookie dough with various flavorings added. We placed the cookie dough in the cage with an adult mouse and recorded the amount ingested after 1 h. Mice readily ingested all flavors of sugar-cookie dough. We then added a euthanasia solution containing pentobarbital and phenytoin to all flavors of cookie dough and placed a small bolus in the cage of each mouse or mouse pair. We observed the mice for 1 h for clinical signs of pentobarbital intoxication and then weighed uneaten dough to determine the dose of pentobarbital ingested. Palatability declined sharply when euthanasia solution was present. Mice ingested higher doses of pentobarbital in cookie dough during the dark phase and after fasting. Ingestion caused ataxia in some mice but was not sufficient to cause loss of righting reflex, unconsciousness, or death in any mouse. We successfully identified sugar cookie dough as a drug vehicle that was readily and rapidly eaten by mice without the need for previous exposure. Additional research is needed to identify euthanasia compounds for mice that do not affect the palatability of cookie dough.

Effects of Topical Anesthetics on Behavior, Plasma Corticosterone, and Blood Glucose Levels after Tail Biopsy of C57BL/6NHSD Mice (Mus musculus).

Tail biopsy is a common procedure that is performed to obtain genetic material for determining genotype of transgenic mice. The use of anesthetics or analgesics is recommended, although identifying safe and effective drugs for this purpose has been challenging. We evaluated the effects of topical 2.5% lidocaine-2.5% prilocaine cream applied to the distal tail tip at 5 or 60 min before biopsy, immersion of the tail tip for 10 seconds in ice-cold 70% ethanol just prior to biopsy, and immersion of the tail tip in 0.5% bupivacaine for 30 s after biopsy. Mice were 7, 11, or 15 d old at the time of tail biopsy. Acute behavioral responses, plasma corticosterone, and blood glucose were measured after biopsy, and body weight and performance in elevated plus maze and open-field tests after weaning. Ice-cold ethanol prior to biopsy prevented acute behavioral responses to biopsy, and both ice-cold ethanol and bupivacaine prevented elevations in corticosterone and blood glucose after biopsy. Tail biopsy with or without anesthesia did not affect body weight or performance on elevated plus maze or open-field tests. We recommend the use of ice-cold ethanol for topical anesthesia prior to tail biopsy in mice 7 to 15 d old.

Physiological, Behavioral, and Histological Responses of Male C57BL/6N Mice to Different CO2 Chamber Replacement Rates.

Rodent euthanasia with CO2 by using gradual displacement of 10% to 30% of the chamber volume per minute is considered acceptable by the AVMA Panel on Euthanasia. However, whether a 50% to 100% chamber replacement rate (CRR) of CO2 is more painful or distressful than 10% to 30% CRR is unclear. Therefore, we examined physiological and behavioral parameters, corticosterone and ACTH levels, and lung histology of mice euthanized at CRR of 15%, 30%, 50%, or 100%. Adult male C57BL/6N mice were euthanized at different CO2 CRR as physiological parameters were recorded telemetrically. Video recordings were reviewed to determine when the mouse first became ataxic, when it was fully recumbent (characterized by the mouse's nose resting on the cage floor), and when breathing stopped. Overall, CO2 euthanasia increased cardiovascular parameters and activity. Specific significant differences that were associated with 50% to 100% compared with 15% to 30% CO2 CRR included an increase in systolic blood pressure per second from initiation of CO2 until ataxia, a decrease in total diastolic blood pressure until ataxia, and a decrease in total heart rate until ataxia, immobility, and death. All physiological responses occurred more rapidly with higher CRR. Activity levels, behavioral responses, plasma adrenocorticotropic hormone and corticosterone levels, and lung pathology were not different between groups. We found no physiological, behavioral, or histologic evidence that 15% or 30% CO2 CRR is less painful or distressful than is 50% or 100% CO2 CRR. We conclude that 50% to 100% CO2 CRR is acceptable for euthanizing adult male C57BL/6N mice.

Effects of repeated petting sessions on leukocyte counts, intestinal parasite prevalence, and plasma cortisol concentration of dogs housed in a county animal shelter.

OBJECTIVE: To describe changes in WBC counts, plasma cortisol concentration, and fecal parasite shedding of dogs housed in an animal shelter and determine the effects of daily petting sessions on these variables. DESIGN: Hybrid prospective observational and experimental study. ANIMALS: 92 healthy dogs newly arrived to an animal shelter and 15 healthy privately owned dogs (control group). PROCEDURES: Blood and fecal samples were collected from shelter dogs 1, 3, and 10 days after arrival and from control dogs once. A subset of shelter dogs (n = 15) was assigned to receive 30 minutes of petting daily. Plasma cortisol concentration was measured, CBCs were performed, and fecal samples were evaluated for parasite ova. RESULTS: For shelter dogs, total leukocyte, neutrophil, and lymphocyte counts increased significantly between days 1 and 10, with less consistent increases in monocyte count and neutrophil-to-lymphocyte count ratio. Parasite shedding was unaffected by duration of shelter stay but was greater for shelter versus control dogs. For shelter dogs, plasma cortisol concentration decreased with time and was higher than that of control dogs on each day. Total leukocyte, neutrophil, and monocyte counts and neutrophil-to-lymphocyte count ratios were also higher for shelter versus control dogs. Petting sessions resulted in a decrease in plasma cortisol concentration but in no other variables. CONCLUSIONS AND CLINICAL RELEVANCE: Large increasing immunologic responses, heavy parasite shedding, and high but decreasing plasma cortisol concentration were identified in shelter dogs. Daily 30-minute petting sessions affected only cortisol values, so the clinical importance of petting for immunologic and other health outcomes remains unclear.

Incidence of dental lesions in musk shrews (Suncus murinus) and their association with sex, age, body weight and diet.

Both wild and laboratory strains of the musk shrew (Suncus murinus) have a high incidence of periodontitis. The authors completed necropsy examinations in 51 shrews to identify dental lesions including tooth loss, mobility and fractures. Dental lesions were identified in significantly more females than males, and older animals were more likely to have lesions present. Shrews with one or more dental lesions weighed significantly less than those without lesions present. Dietary supplementation with mealworms did not significantly affect the incidence of dental lesions or the body weight of male or female shrews. The authors recommend routine body weight measurement as a simple, noninvasive method of detecting shrews with an increased likelihood of having dental lesions.

Gastric volvulus in guinea pigs: comparison with other species.

Gastric volvulus has been documented in several species of animals and is associated with high morbidity and mortality. We report 2 cases of gastric volvulus in guinea pigs that died without detection of prior clinical signs. Both guinea pigs were adult female guinea pigs in a breeding colony and had given birth to multiple litters; one was pregnant at the time of death. Gastric rotations of 540° and 360° were identified at necropsy examination. These cases include the first known report of gastric rotation greater than 360° in any species. Although gastric volvulus has been reported to occur in guinea pigs, little is known about its risk factors, etiology, and pathogenesis. We conducted a literature review to compare gastric volvulus between guinea pigs and other species.

Healing of iatrogenic skeletal muscle wounds is affected by incision device.

Orthopedic joint procedures frequently require extensive dissection of skeletal muscles resulting in tissue injury, formation of scar tissue, pain, and potentially, functional impairment. The authors hypothesized that using a low-temperature ultrasonic cutting and coagulating device (Harmonic Blade, Ethicon Endo-Surgery, Cincinnati, OH) would result in reduction in tissue trauma in terms of reducing acute and chronic inflammation during healing. Bilateral longitudinal incisions were made into the tibialis cranialis muscles of rabbits with either a Harmonic Blade or a standard monopolar electrosurgical scalpel. At 3, 7, and 21 days postoperatively, necropsy and histological evaluations indicated a significant attenuation of acute inflammation (P = .011) for the Harmonic incisions compared with electrosurgery. No significant differences were observed for chronic inflammation, necrosis, or fibrosis. Use of a Harmonic scalpel during dissection of skeletal muscle in orthopedic surgery may result in reduced influx of neutrophils, reducing acute inflammation, and potentially aid in reducing postoperative pain and functional impairment.