The goal of this retrospective study was to determine whether having added tiletamine–zolazepam to an anesthetic cocktail of ketamine and xylazine (KX) during an ongoing series of studies of renal function in domestic pigs changed baseline renal hemodynamics. Group A (10 pigs) had been anesthetized with KX, group B (25 pigs) was anesthetized with tiletamine–zolazepam combined with KX (TKX), and group C (10 pigs) was anesthetized with KX. Measurements of baseline glomerular filtration rate (GFR; inulin clearance), effective renal plasma flow (eRPF; para-aminohippuric acid clearance), and mean blood pressure (BP) were made during three 15-min urine collection periods. GFR and eRPF were lower in group B (TKX) than in groups A and C (KX only) by 34% to 40% and 39% to 49%, respectively. BP did not differ between the 3 groups. GFR and eRPF in groups A and C were not different from each other. These findings suggest that adding tiletamine–zolazepam to an anesthetic cocktail can cause an acute decline in GFR and eRPF independent of arterial BP in laboratory swine.
Accurate postoperative pain management is crucial for good animal welfare and science. We sought to evaluate mouse postoperative pain management efficacy by measuring activity using a novel triaxial acceleration device—the Rodent Fitbit-like telemetry device (RFB)—to monitor home cage activity. To determine if analgesics impacted activity levels, we evaluated activity in C57BL/6 male and female mice (n = 6) that were attached with the RFB and administered EthiqaXR (XR; 3.25 mg/kg), meloxicam sustained release (MSR; 6 mg/kg), combined XR/MSR, or bupivacaine (5 mg/mL) compared with control mice provided sterile saline (5 mL/kg) subcutaneously. Activity in XR/MSR and XR-treated mice was significantly increased on night 0 (N0) but only trended downward from N2 to N4 compared with baseline. No significant changes in activity were detected after administration of MSR, bupivacaine, and saline. We examined the effective analgesic period of XR, MSR, XR/MSR, and bupivacaine based on electric von Frey and the RFB using a hind paw incision pain model in C57BL/6 male (n = 8) and female mice (n = 7) attached with the RFB. Preoperative XR and XR/MSR mice had reduced pain based on von Frey with no reduction in activity based on the RFB compared with other treatment groups. Only mice provided saline demonstrated a significant decrease in activity on N0, suggesting limited duration of spontaneous pain elicited from the minor pain model. In summary, activity was an effective and sensitive indicator for detecting pain using a paw incision pain model in C57BL/6 mice within the first 24 h postsurgery. Additional studies using a major operative procedure should be performed to determine the effectiveness of activity as a pain detection indicator.
Porcine models can potentially bridge the gap between basic studies and clinical trials in humans due to their homologous similarities; the pig model aids in understanding the pathophysiology of diabetes. Continuous glucose monitoring is crucial for precise insulin control in this disease. Although the use of glucose sensors has been described in the literature, details relating to placement of the sensor are not provided. Hence, we describe here, in detail, the insertion, placement, and fixation of the sensor for continuous glucose level monitoring and its use in diabetes mellitus studies in swine. Four male minipigs, weighing 15 to 22 kg and aged 10 mo, were used and underwent induction of diabetes using streptozotocin. The sensors were placed on the 4 pigs to enable continuous glucose monitoring throughout the study (35 d), with sensor changes every 7 d. The results obtained allow us to consistently track changes in glucose. In conclusion, this article highlights the methodology’s effectiveness and reinforces its practical applicability in obtaining reliable results for analyzing trends in interstitial glucose levels, thus further optimizing the swine model for diabetes research.
The use of hydrochloric acid treatment of drinking water in many academic research rodent colonies and commercial vendors prompted us to investigate its effect on tooth enamel health in mice. Drinks with a low pH such as fruit juices and soft drinks have been demonstrated to cause demineralization of tooth enamel in humans and rodents. This study explored the hypothesis that acidified drinking water at the recommended range of 2.5 to 3.0 pH can lead to enamel erosion and compromised tooth integrity in mice. Specifically, we sought to quantify the effects of pH 2.5 or 3.0 daily drinking water exposure on molar enamel and bone mineral density over 1 and 3 mo. Methylene blue was used to quantify enamel erosion of the molar teeth, while dual-energy X-ray absorptiometry was used to quantify the bone mineral density of the mandible. After 1 mo of drinking water exposure, no statistically significant difference between the groups in enamel erosion or bone mineral density was observed. However, after 3 mo, a significant difference in enamel erosion for the pH 2.5 group compared with the other groups was identified, suggesting a potentially destructive process. There were no differences in bone mineral density between groups at any time point. These findings indicate that acidified drinking water of pH 2.5 may have deleterious effects on the enamel integrity of molar teeth in mice; however, drinking water of pH 3.0 seems safe for tooth enamel in mice during a short-term exposure of 3 mo. As this study only had a 1- to 3-mo exposure period, further study is needed to determine the effects of longer-term use of acidified drinking water at pH 3.0 in mice.
Intraperitoneal injections are commonly used for systemic drug administration in various laboratory animals, including rodents and zebrafish (Danio rerio). Although these fish have rapidly gained popularity in biomedical research, the accuracy of intraperitoneal drug delivery (due to potential leakage from the injection site) has not been previously evaluated in zebrafish. To investigate this issue, we injected adult zebrafish with 10 µL/g of a dye (1% Evans Blue) intraperitoneally and estimated dye leakage by measuring the optical density of water where the fish were kept for 20 min past injection. Overall, we found that intraperitoneal injections resulted in an estimated approximately 10% immediate leakage and approximately 0.01% secondary leakage (of the injected dye volume), confirming the relative accuracy of intraperitoneal injection as a reliable drug delivery method in adult zebrafish.
Rodent health monitoring (HM) programs are designed to detect infectious agents in rodents that have the potential to negatively impact animal health or research findings. These programs are an essential component for verifying the desired health status of a research mouse colony. While multiple factors can provide information about a colony’s health status, including clinical observations, gross and microscopic pathologies, unexpected experimental results, and other factors, the term ‘health monitoring program’ in this review refers specifically to the routine screening/testing of laboratory mice or their environment for the presence (for example, by bacterial culture or visual identification or ectoparasites)Introduction
Behavioral tests in laboratory animals, particularly rodents, are considered vital for understanding the mechanisms underlying depression and evaluating potential treatments. However, ethical concerns regarding the use of traditional methods, such as the tail suspension test and the forced swimming test, which induce significant distress, have led to calls for more humane alternatives. In this paper we explore the ethical considerations surrounding common behavioral tests used in depression research, focusing on the tail suspension test’s and forced swimming test’s potential to cause harm to animals and their controversial relevance to human depression. Alternative methods, including the nest building behavior assessment and social interaction observations, provide valuable insights into depression-like behaviors without inducing unnecessary stress. We advocate for a shift toward mild-stress testing methods aligned with the 3Rs principle (replacement, reduction, and refinement). By integrating these humane practices, and promoting education on alternative methods, the scientific community can enhance the ethical integrity and translational relevance of preclinical depression research.
Grapiprant belongs to the newer piprant class of nonsteroidal anti-inflammatory drugs (NSAIDs) and is FDA approved for treatment of osteoarthritis in dogs. The compounds act as an antagonist at the prostaglandin E2 EP4 receptor and is therefore also noncyclooxygenase inhibiting. This mechanism of action reduces the potential for adverse side effects associated with cyclooxygenase inhibition and makes it a promising drug for long-term use in nonhuman primates (NHPs) with chronic inflammatory conditions. In this study, we sought to establish pharmacokinetic parameters of an oral oil suspension of grapiprant in healthy, fasted male and female rhesus macaques (Macaca mulatta) with a single oral dose of 2 mg/kg, the current FDA-approved dose in dogs. Blood was collected at time 0 (baseline) and at 9 additional time points (0.25, 0.5, 1, 2, 4, 8, 12, 24, and 48 h) after dosing. Grapiprant plasma concentration was quantified using liquid chromatography–tandem mass spectrometry. Our data show that rhesus macaques absorb grapiprant more slowly (Tmax = 2 h for all subjects) and at a lower level (Cmax = 23.8 ± 19.6 ng/mL, AUClast = 77.5 ± 42.9 ng·h/mL) than published values in dogs. No significant difference was noted in pharmacokinetic parameters between males and females; however, females showed more variability in pharmacokinetic parameters than did males. Significant age effects were not observed, although a positive correlation between Cmax and AUClast with age in males was noted. Our data suggest that higher doses should be explored in rhesus macaques, with a need for further investigation into the pharmacodynamics of grapiprant to establish an efficacious therapeutic dose in this species and other NHPs.
Stress in research animals affects their welfare and alters physiologic responses, potentially impacting research outcomes. Laboratory rodents often experience stress from repeated parenteral drug administrations due to handling and needle punctures. In this study, we compared the efficacy of oral carprofen tablets and carprofen-treated nutritional gels compared with injectable carprofen for alleviation of postoperative mechanical and thermal hypersensitivity in NSG mice. Male and female mice (n = 59) were randomly assigned to one of 5 groups: 1) placebo (Placebo tablets or NutraGel, daily); 2) carprofen tablets (CarpTab; 2 mg, daily); and 3) carprofen injection (Carp25SC; 25 mg/kg SC, daily), low-dose carprofen-treated gels (CarpGel-low; 0.11 mg/mL, daily); and high-dose carprofen-treated gels (CarpGel-high; 0.22 mg/mL, daily). Mechanical and thermal hypersensitivities were assessed before surgery on D-1 and at D0 (4 h), D1, and D2 afterward. Plasma carprofen concentration (n = 56) was assessed over 1 to 4 d. Daily clinical observations, fecal occult blood testing, and gross necropsies were performed. Results showed that mechanical and thermal hypersensitivity persisted in the placebo group throughout the study (D0 to D2). CarpTab and Carp25SC groups effectively attenuated mechanical hypersensitivity compared with the baseline (D0 to D2). Compared with baseline, CarpGel-low attenuated mechanical hypersensitivity on D1 and CarpGel-high attenuated mechanical hypersensitivity on D2. All carprofen treatment groups, except CarpGel-high at D0, attenuated mechanical hypersensitivity compared with placebo. Thermal hypersensitivity persisted in all carprofen treatment groups compared with baseline values. However, compared with placebo, CarpTab, Carp25SC, and CarpGel-low provided attenuation of thermal hypersensitivity. Plasma carprofen concentrations did not significantly differ among oral formulations. Fecal occult blood testing was positive only in 1 of 6 mice in the CarpGel-high group at 1 and 2 d after administration. These findings support the use of orally administered CarpTab as an alternative analgesic to Carp25SC for incisional pain in NSG mice.
The Guide for the Care and Use of Laboratory Animals provides recommendations on sanitation frequencies for rodent caging equipment; however, it allows for performance standards to be used when extending this frequency for individually ventilated cage (IVC) caging. Our institution wanted to reexamine our current standards of care for mouse IVC caging, which includes a 14-d cage bottom and bedding change as well as the use of corncob bedding. This was driven by desire to reduce the stress to mice associated with cage change, and by recent literature showing a potential improved absorbency and multiple health and welfare benefits of paper pulp cellulose bedding products. Therefore, this study sought to compare the impact of different rodent bedding types (paper pulp cellulose and corncob) on mouse IVC microenvironmental parameters over a 14-d compared with a 21-d cage change frequency. Ammonia levels, temperature, humidity, urine latrine size, and the overall animal condition were assessed throughout the 21-d period. Our data indicate that IVC cage bottom and bedding change can be extended to 21 d for either paper pulp cellulose or corncob bedding based on ammonia levels, temperature, humidity, and the animal’s overall condition. However, based on early cage change criteria, more frequent cage changes may be warranted before 21 d in cages with corncob, as there was a significantly increased urine latrine size in cages with corncob bedding compared with paper pulp cellulose bedding.
Demodex musculi is a microscopic mite that inhabits the hair follicles of mice. It is the most frequently diagnosed mite in laboratory colonies and infests up to 13% of mice shipped from noncommercial vendors. Depending on the mouse infested, D. musculi may cause immunomodulation or debilitating clinical signs that can impact experimental reproducibility. Current treatment options are limited, and many infested mice are ultimately euthanized. Fluralaner, an isoxazoline-class ectoparasiticide, successfully treats demodicosis in other species. However, to our knowledge, its efficacy in treating demodicosis in mice has not been reported. This study aimed to explore the effects of 2 different doses of topical fluralaner for the treatment of D. musculi in NSG mice. We hypothesized that both doses of topical fluralaner would eliminate infestations in all animals. Female NSG mice infested with D. musculi were treated with topical fluralaner at 2 different doses (100 mg/kg or 250 mg/kg) every 2 wk for 4 treatments. Efficacy was determined by routine deep skin scrapes, fur plucks, quantitative PCR, and a pelt scroll histologic analysis. All diagnostic modalities indicated that no cage in either treatment group was successfully cleared of mites. However, quantitative PCR indicated a significant reduction in mite burden following treatments. After treatments ceased, mite burden remained similar between time points and then increased. There were no significant differences in mite burden between treatment groups at any time point. These data suggest that topical fluralaner could be useful in treating D. musculi infestations in NSG mice. However, additional research is needed to determine if higher and/or more frequent doses will improve efficacy.
An effective rodent pest control program is an important aspect of any animal care and use program. It ensures the SPF status of rodent colonies and also protects human safety as regards zoonoses prevention. According to the AVMA Guidelines for Euthanasia of Animals, kill traps do not always render a rapid or stress-free death, and thus, the use of live traps followed by euthanasia is preferred; however, they also state that, although newer technologies improve kill trap performance by assuring rapid loss of consciousness, individual testing of traps is recommended to ensure the device works properly. Here, we evaluated an electrical shock trap as an option for vermin control in animal facilities. We assessed the trap’s ability to quickly induce irreversible loss of consciousness and death with minimal pain and distress. This was performed by placing a modified trap (allowing visualization of the animal’s interaction within the trap) in a test chamber and allowing animals to freely interact with the trap. Assays were videotaped by an overhead and a side camera. We measured time to induce loss of consciousness and time to death using male (n = 10) and female (n = 10) Crl:CFW(SW) mice. A subset of electrical shock (n = 10) and CO2 (n = 4) euthanized animals were used for blinded comparative necropsy and histopathology. Our results indicate that the trap has a 100% kill rate. Mean time to unconsciousness was 7.35 ± 3.76 s, while mean time from unconsciousness to death was 25.62 ± 7.2 s. Histopathology revealed a 20% (2/10) occurrence of focal mild dermal lesions, indicative of perimortem burn injury, in the electrical shock animals. No other histologic changes associated with electrocution were identified. In conclusion, this system presents a viable alternative to current mouse traps, while improving animal welfare compared with other kill trap options, as well as allowing reduced labor investment associated with pest control management.
The previous article republished in this series was a review that covered some of the background, history, and genetics of the “Swiss” mouse stock. The installment in this issue is a rat-related follow-up. For the October 1969 issue of Laboratory Animal Care, in addition to the standard journal content (published as Part I), there was a second special issue released as Part II. This was composed of papers originally presented earlier in the year at a symposium sponsored by the New York Metropolitan Branch of AALAS entitled “The Long-Evans Rat in Biomedical Research.” The 11 articles comprising the
Gavage-Needle Voluntary Consumption Administration of a Dose-Specific Measure to Mice (Mus musculus)
Orogastric gavage is a common technique used to administer test articles to rodents with risks ranging from increased stress to death of the animal. In this study, we propose a novel technique to administer treatments to mice for voluntary consumption through a plastic gavage needle: gavage-needle voluntary consumption (GVC) with a sweetened condensed milk carrier. GVC was successful at orally dosing mice in 95.0% (n = 459) of 483 total GVC opportunities. BALB/c mice (n = 61 [27 males/34 females] for analysis) were randomized into 8 intervention-treatment groups with 2 treatment allocations. Mice habituated to the GVC technique in less than 5 d and continued to consume the condensed milk with or without capromorelin for a 3-d treatment period that commenced after receiving their assigned interventions. The GVC technique allowed for efficient transition to orogastric gavage when the treatment was not consumed in 3.8% (n = 7) of 183 GVC attempts in the treatment period, thereby ensuring that every mouse received its treatment. The proportion of mice that consumed their treatments voluntarily was not affected by the intervention the mice received prior to the treatment period but was affected by the addition of the treatment article capromorelin. It is recommended to consider the GVC technique as a replacement and refinement to oral gavage when orogastric administration of treatments to mice is required.
The common marmoset (Callithrix jacchus) is an increasingly popular animal model, and while carprofen is a frequently used NSAID in this species, there are no published studies evaluating dosage needs to achieve appropriate analgesia. The aim of this study was to determine the pharmacokinetics of low-dose (2 mg/kg) and high-dose (4 mg/kg) carprofen following oral and subcutaneous routes of administration in marmosets. Three (2 females, 1 male) adult (3.1 ± 1.6 y old [mean ± SD]) common marmosets were used for this study. Blood was collected at 0, 1, 2, 4, 6, 12, and 24 h after administration. The plasma concentrations of carprofen were determined using HPLC and pharmacokinetic parameters. The 4 mg/kg carprofen yielded a significantly higher plasma concentration than did 2 mg/kg carprofen. However, our data show that neither administration route, nor dose, result in plasma concentrations at or above the desired therapeutic threshold. The poor pharmacokinetic properties suggest that these doses of carprofen are not adequate and that either higher doses should be considered or carprofen should not be used as the NSAID of choice in the common marmoset.
Early detection of pathogens is imperative for the health of laboratory zebrafish and to ensure reproducible scientific results. While most pathogens are present as subclinical or chronic infections, their presence can be a confounding factor in data collection, and some infections can affect zebrafish health and reproduction. Current methods to test for pathogens sample myriad sources, including sump swabs, detritus, water collection or filtration, and whole-fish PCR or histopathology. Sentinel mice have been used in the past for mouse health monitoring, but there has been a recent shift to replace sentinel animals with filters in rack exhausts. We wanted to determine whether such methods could be translated from mouse racks to zebrafish systems. First, we tested whether nitrocellulose filters would affect the health and behavior of adult and larval zebrafish and found no adversary effects. Next, we placed filters in the sumps of zebrafish racks to be collected and tested for pathogens at monthly intervals using PCR, and results were compared with those detected on filters in which water was actively vacuum pumped through or swabs of sump biofilm. Results suggest that the efficacy of filters may wane with prolonged use, with sensitivity being greatest at 60 d and then decreasing at 90 d. Results also showed the limitations of current testing methods for zebrafish health monitoring, with efficacy of detecting pathogens varying widely based on the method of collection. Our recommendation is to test the filters after 6 wk of exposure, and supplement with whole-fish testing of clinically ill fish.
The soles of staff shoes accessing vivaria can become contaminated on urban streets, potentially serving as a source of fomite-mediated transmission of adventitious agents to laboratory rodents. While shoe covers may mitigate this risk, donning them can lead to hand contamination. Staff accessing our vivaria use motor-driven shoe cleaners hundreds of times daily to remove and collect particulates via a vacuum collection system from the top, sole, and sides of shoes instead of shoe covers. Shoe cleaner debris (SCD) and contact media (CM) exposed to SCD from shoe cleaners in 5 vivaria were assessed by PCR for 84 adventitious agents. SCD and CM samples tested positive for 33 and 37 agents, respectively, and a combined 39 agents total. To assess SCD infectivity, NSG (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) and Swiss outbred mice were housed for 7 d in direct contact with SCD and oronasally inoculated with a suspension created from SCD collected from each of the 5 vivaria. Mice were tested by PCR and serology at 3, 7, 14, and 63 d postinoculation. All mice remained healthy until the study’s end and tested negative for all agents found in SCD/CM except murine astrovirus 1, Staphylococcus xylosus, and Candidatus Savagella, agents known to be enzootic in the experimental mouse source colony. In a follow-up study, the soles of 27 staff street shoes were directly sampled using CM. Half of CM was used for PCR, while the other half was added as bedding material to a cage containing NSG and Swiss outbred mice. While CM tested positive for 11 agents, all mice were healthy at 63 d postexposure and again positive for only enzootic agents. These results suggest that shoe debris might not be a significant biosecurity risk to laboratory mice, questioning the need for shoe covers or cleaners when entering experimental barrier vivaria.
Lidocaine infusions are used in several species to reduce anesthetic requirements and decrease the negative impact of high inhalant concentrations on the cardiorespiratory system. The objective of this study was to determine the effect of 2 dosages of lidocaine administered as constant rate infusions on isoflurane requirement (IR) in swine and to measure plasma concentrations of lidocaine and, its metabolite, monoethylglycinexylidide (MEGX) corresponding to IR. Six healthy commercial-bred pigs aged 74 ± 5.3 d and weighing 31.7 ± 5.4 kg were anesthetized and maintained with isoflurane during mechanical ventilation. Baseline IR was determined using a supramaximal mechanical stimulus on the dewclaw of the hind limb. After randomization for treatment allocation, lidocaine (loading dose; 2 mg/kg IV) was administered, followed by either 50 (CRI50) or 200 (CRI200) µg/kg/min and maintained for 30 min to reach a steady state and redetermination of IR. The study was repeated with the alternate infusion rate after a minimum washout period of 6 d. Lidocaine and MEGX plasma concentrations were quantified with HPLC and compared between groups. Heart rate, arterial blood pressure, end-tidal partial pressure of carbon dioxide, body temperature, and time to extubation were measured and compared between treatment groups. Baseline IR was 1.77% ± 0.34%. In pigs receiving CRI50 (1.53%) and CRI200 (1.61%), IR was lower than baseline IR, with a sparing effect of 7.8% (P = 0.046) and 13.4% (P = 0.041), respectively. Plasma concentrations of MEGX were inversely correlated to IR in pigs receiving CRI50 but not CRI200. Cardiovascular variables did not differ between treatments. Time to extubation was similar between groups (P = 0.92), 10.2 ± 4.5 min in subjects receiving CRI50 and 11 ± 3.6 min in pigs receiving CRI200. Infusion of lidocaine produced a nonlinear sparing effect on isoflurane requirement without appreciable, clinically relevant changes in cardiovascular variables or extubation time.
Mice are commonly anesthetized (or sedated) with drugs injected via the intraperitoneal or subcutaneous interscapular routes. The Governing Vessel 20 (GV20) site, located at the top of the head, is an alternative subcutaneous injection route, shown to be successful in dogs and cats. In a multicenter, randomized, blinded study design, C57BL/6 mice (n = 66: 60 males, 6 females) were assigned to injection with ketamine (60 mg/kg) and xylazine (5 mg/kg). Injection distributions were as follows: site 1, GV20 (n = 10) and intraperitoneal (n = 9); site 2, GV20 (n = 16), interscapular subcutaneous (n = 15), and intraperitoneal (n = 16). Outcome measures were times to ataxia, sternal recumbency, and the loss of righting reflex. Data from sites 1 and 2 were pooled following confirmation that there were no significant differences (Mann–Whitney test). Outcome measures were compared between injection routes with a Kruskal–Wallis test followed by a Dunn multiple comparisons test. Results are reported as median (range) times. Intraperitoneal injection was faster acting than the other injection routes, and there were no significant differences between the GV20 and interscapular subcutaneous routes: ataxia (GV20, 187.0 s [120 to 272]; subcutaneous, 165.0 s [120 to 372]; intraperitoneal, 88.5 s [58 to 171]), sternal recumbency (GV20, 305.5 s [153 to 400], subcutaneous, 305.0 s [249 to 384]; intraperitoneal, 184.5 s [120 to 397]), loss of righting reflex (GV20, 399.0 s [208 to 589]; subcutaneous, 347.0 s [249 to 468]; intraperitoneal, 190.0 s [142 to 402]). In summary, the GV20 subcutaneous injection route does not appear to have benefits compared with the intraperitoneal route and is not superior to the interscapular subcutaneous injection route in C57BL/6 mice when evaluated using a combination of ketamine and xylazine.
Housing in metabolic cages for quantitative collection of urine and feces is necessary for nitrogen (N) metabolism studies but may have negative consequences for rat welfare. We hypothesized that providing shelters in metabolic cages would affect the rats’ behavior and reduce the precision of measuring N metabolism. Forty-eight growing male Sprague–Dawley rats were housed in metabolic cages for 9 d, constituting 4 d of adaptation and 5 d for quantitative measurement of feed intake and urine and feces excretion. Using a 2-factorial approach, half of the rats were fed a soybean meal diet, and the other half were fed a diet based on green protein (GP). Half of the rats in each dietary group were provided a ball-shaped shelter in their metabolic cage, and the other half had no shelter (n = 12 per treatment). Video recordings of rat location (cage floor, feed tube, or shelter) were performed on days −3 (adaptation period), 1, and 4 (collection period). Dry matter (DM) and nitrogen (N) digestibility were determined based on DM and N intake and fecal excretion. N metabolism was calculated based on additional measurements of urinary N excretion. The rats used the shelter primarily during the daytime and spent less time in the feed tube during the day than during the night (P = 0.0002). For rats without shelter, there was no difference between day and night in their presence in the feed tube (P = 0.94). The shelters did not interfere with measurements of feed intake, fecal DM, N excretion, or any of the derived N-metabolism-associated responses. There was also no significant effect on the variation associated with the estimated values, and no differences in contamination were detected visually or by rinsing the shelters. We conclude that using ball-shaped shelters to enrich metabolic cages is not a major risk of biocontamination and may improve the rats’ welfare.
While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechani- cal pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague–Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.Abstract
The Whitten effect is a widely used tool for manipulating the mouse estrous cycle and generating reproductively active females within the laboratory setting. Typically, peak numbers of sexually receptive mice occur following exposure to male pheromones, resulting in a higher number of successful copulations on the third day after exposure. Although this method has improved efficiencies, the percentage of females mated and subsequently deemed to be pregnant/pseudopregnant remains relatively low, around 50%. In experiment 1, we aimed to 1) further understand cyclicity; 2) determine whether the initial cycle stage plays an importance on day 3 receptivity; and 3) identify any repetitive patterns/cycle stabilization. Mice (n = 27) were assigned to group cages according to cycle stage (proestrus, estrus, metestrus, diestrus). Experiment 2 was developed to determine an optimum treatment to promote receptivity by exposure to various pheromone stimuli. Mice (n = 45) were randomly assigned to 5 treatment groups (PBS-treated sham soiled bedding, male soiled bedding, live male, pregnant females, and lactating females). In both experiments, daily vaginal cytology was performed for 21 days to determine the cycle stage. Results from experiment 1 indicate that the initial cycle stage did not contribute to day 3 receptivity, although synchronization within several groups/cages was noted, and that the greatest numbers of estrous animals were obtained on days 6 and 7. Experiment 2 revealed that exposure to live males and lactating females both significantly improved receptivity compared with the PBS, male soiled bedding, and pregnant female groups. These results indicate that current strategies used for routine synchronization could be further improved through alternative housing regimens without compromising animal welfare.Abstract