Evaluation of Various IVC Systems According to Mouse Reproductive Performance and Husbandry and Environmental Parameters

IVC systems are marketed for improving the health and management of mouse colonies. The current study compared mouse reproductive performance and husbandry and environmental parameters among 3 high-density (HD) IVC rack systems (RS1, RS2, and RS3), which were present in separate but comparable rooms. Three breeding trios each of Swiss Webster (CFW) and BALB/c mice were placed in each rack (n = 36 female, n = 18 male). Reproductive indices were measured for 3 breeding cycles over 2 generations; indices included time to parturition, litter size and pup weight, survivability, and interbirth interval. Over 18 wk, personnel used scoring systems to evaluate each RS daily to every other week according to cage dirtiness, need for spot changing, ease of cage changing, daily health checks, and cage wash processing. Macroenvironmental parameters (temperature, relative humidity, noise, total particulate matter) were measured weekly over 14 wks. Microenvironmental parameters (temperature, relative humidity, NH3, CO2, O2) of 2 cages each of male and female CFW mice (4 mice/cage) on each RS were measured at 6 time points over 2 wks. RS1 had significantly smaller mean litter sizes of CFW mice (mean ± 1 SD, 6.5 ± 2.9 pups) as compared with both RS2 (9.5 ± 1.7 pups) and RS3 (9.3 ± 3.8 pups). RS1 scored as beingsignificantly easier to process through the cage wash. RS2 had significantly lower room noise levels (46.0 ± 5.0 dBA) but higher humidity (58.6% ± 8.9%) as compared with both RS1 (43.7% ± 9.9%) and RS3 (46.0% ± 12.0%) over the 2-wk cycle, particularly at 8 and 12 d after cage change. In conclusion, in terms of mouse reproductive performance and husbandry and environmental parameters, each system had at least 1 advantage over the other 2. Therefore, various factors should be considered when choosing an IVC system for mice.

Influence of Pair-housing on Sleep Parameters Evaluated with Actigraphy in Female Rhesus Monkeys

Rhesus monkeys are naturally social animals, and behavioral management strategies have focused on promoting pairhousingin laboratory settings as an alternative to individual or group housing. In humans, co-sleeping can have a major impact on bed partners’ sleep, raising the possibility that pair-housing also may influence sleep parameters in monkeys. In the present study, we investigated if pair-housing would impact home-cage partner’s sleep in female rhesus monkeys, and if nighttime separation using socialization panels would alter this pattern. Sleep parameters of 10 experimentally naïve adult female rhesus monkeys (5 pairs) were evaluated for 7 consecutive days using actigraphy monitors attached to primate collars. Paired animals then were separated by socialization panels during the night, and sleep-associated measures were evaluated for 7 consecutive days. The data showed that sleep efficiency was significantly lower when monkeys were pairhoused as compared with when they were separated. On the nights when subjects were pair-housed, a positive correlation was detected for sleep measures (both sleep latency and efficiency) of both members of a pair (R2’s = 0.16–0.5), suggesting that pair-housing influences sleep quality. On nights when subjects were separated, no correlations were observed for sleep measures between members of the pairs (R2’s = 0.004–0.01), suggesting that when separated, the home-cage partner’s sleep no longer influenced the partner’s sleep. Our results indicate that pair-housing has a strong impact on the home-cage partner’s sleep, and that this pattern can be prevented by nighttime separation using socialization panels. Studies evaluating sleep in pair-housed monkeys should consider the effects that the partner’s sleep may have on the subject’s sleep. Sleep is a biologic phenomenon and experimental outcome that affects physical and behavioral health and altered sleep due to pair-housing may affect a range of research outcomes.

Short-Term Housing in Metabolic Caging on Measures of Energy and Fluid Balance in Male C57BL/6J Mice (Mus musculus)

Metabolic caging is an important tool for quantitative urine and feces collection in rodents, although significant limitationsand problems accompany its use. Despite strong opinions among investigators regarding the effects of metabolic caging onenergy and fluid homeostasis, careful quantitative analysis of the impact of this caging type—particularly when used for mice—is lacking. The current study assessed the effects of metabolic caging, with or without modifications such as plastic platform inserts, on ingestive behaviors, energy expenditure, accuracy of urine and fecal collection, and ambulatory activities in male C57BL/6J mice. Housing mice in metabolic cages, regardless of platform inclusion, increased energy expenditure without modifying food intake, presumably due to the inability of mice to perform normal thermoregulatory behaviors (burrowing and huddling). Surprisingly, mice in metabolic cages actively avoided platforms, and the inclusion of platforms modified the behavior of the mice and had position-dependent effects that reduced the accuracy of urine collection. Moving mice from cohousing to individual housing in home cages also increased ingestive behaviors and energy expenditure. We conclude that single housing of male C57BL/6J mice increases energy expenditure, that this increase is potentiated in metaboliccaging conditions, and that platforms in metabolic cages alter mouse behavior and urine collection. Additional future workis needed to determine the potential benefits of using higher ambient temperature for studies of mice in metabolic cagingand whether the above effects occur in females and other strains of mice and other rodent species.

Factors Affecting Hematologic and Serum Biochemical Parameters in Healthy Common Marmosets (Callithrix jacchus)

Physiologic changes during development, aging, and pregnancy may affect clinical parameters. Previously available reference values have been based on samples that may include wild and captive marmosets, with little representation of geriatricor pregnant animals. Establishing reference values under various conditions would support better recognition of pathologic conditions in marmosets. One hundred and forty-seven (70 males and 77 females) healthy marmosets from a research colony were included in this study. Exclusion criteria were abnormal physical exam findings at the time of blood sampling, chronicmedications, or clinical or pathologic evidence of disease. Reference intervals were calculated for serum chemistry andhematology. Using metadata, samples were classified based on age, sex, colony source and pregnancy status. Multiple testsindicated significant differences with varying effect sizes, indicating that developing reference intervals based on metadatacan be useful. Across all the comparisons, medium or large effect sizes were observed most frequently in blood urea nitrogen (BUN), calcium, total protein, alkaline phosphatase (ALP), weight and serum albumin. We report normative clinical pathologic data for captive common marmosets through all life stages and reproductive status. Significant differences were observed in most parameters when stratifying data based on age, sex, colony source, or pregnancy, suggesting that developing reference intervals considering this information is important for clinicians.

Performance and Consistency of Circulating Warm Water Blankets for Rodents

General anesthesia as used for rodent research can have adverse effects on physiologic mechanisms. Thermoregulation is often greatly inhibited, with resultant deleterious effects on cardiac and respiratory function. These potential effects can be mitigated by providing external heat support. The circulating warm water blanket and associated heat pump are often used in rodent procedures. The current study demonstrated that the heating pump and water blanket require quality control assessment to ensure adequate function. Our data showed that of the 6 pumps tested, 5 were able to achieve a temperature thatmet or exceeded the documented thermoneutral zone for mice. Pumps required 20 min of warming to reach their maximal attainable temperatures for the designated user setting. Although the pumps reached a temperature that was sufficient toprovide external thermal support, only 1 of the 6 pumps reached the temperature that was set by the user during the trial.Surface temperatures across the water blanket were recorded to analyze whether a difference in heat support was influencedby animal placement along the water blanket; however, the location points did not yield statistically different results. Two pumps were eliminated from the study due to failure to pass the preparation phase of the trial. The results of this studysupport the need for facilities to establish quality control measures to ensure that heat support systems are functioning at a level required to maintain normothermia during anesthetic procedures.

Improving the Quality of EDTA-treated Blood Specimens from Mice

Nonterminal blood sampling in laboratory mice is a very common procedure. With the goal of improving animal welfare, different sampling sites and methods have been compared but have not achieved a consensus. Moreover, most of these studies overlooked the quality of blood specimens collected. The main preanalytical concern with EDTA-treated blood specimens for hematology analyses is platelet aggregation, which is known to cause analytical errors. Our objective was to find a nonterminal blood sampling method with minimal adverse effects on mice and few or no platelet aggregates. We tested and compared 2 collection sites, 4 sampling methods, and 3 antithrombotic drugs in 80 C57BL6/j male and female mice by evaluating platelet aggregates on blood smears and platelet, WBC, and RBC counts. In addition, the blood collection process was carefully evaluated, and adverse effects were recorded. Platelet aggregation was lower in specimens collected from the jugular vein than from the facial vein, with no effect of the sampling device or the presence of an antithrombotic additive. Highly aggregated specimens were significantly associated with lower platelet counts, whereas aggregation had no effect on WBC or RBC counts. Adverse events during sampling were significantly associated with more numerous platelet aggregates. The jugular vein is thus a satisfactory sampling site in mice in terms of both animal welfare and low platelet aggregation. Using antithrombotic agents appears to be unnecessary, whereas improving sampling conditions remains a key requirement to ensure the quality of EDTA-treated blood specimens from mice.

Assessment of Microbial Reduction by Cage Washing and Thermal Disinfection using Quantitative Biologic Indicators for Spores, Viruses and Vegetative Bacteria

Cage washing is a key process of the biosecurity program in rodent facilities. For the current study, we developed systems (i. e., magnet attachments, quantitative biologic indicators (Q-BI), and measurement of thermal disinfection at equipment level) to assess the microbial decontamination achieved by a rodent equipment washer with and without thermal disinfection. 99% of the magnets remained in position to hold Q-BI and temperature probes inside cages, water bottles or at equipment level across a cabinet washer chamber with loads dedicated to either housing or drinking devices. Various types of Q-BI for Bacillus atrophaeus, Enterococcus hirae and minute virus of mice were tested. To simulate potential interference from biologic material and animal waste during cage processing, Q-BI contained test soil: bovine serum albumin with or without feces. As a quantitative indicator of microbial decontamination, the reduction factor was calculated by comparing microbial load of processed Q-BI with unprocessed controls. We detected variation between Q-BI types and assessed the washer's ability to reduce microbial load on equipment. Reduction factor results were consistent with the Q-BI type and showed that the washing and thermal disinfection cycle could reduce loads of vegetative bacteria, virus and spore by 5 log10 CFU/TCID50 and beyond. Thermal disinfection was monitored with temperature probes linked to data loggers recording live. We measured the period of exposure to temperatures above 82.2 °C, to calculate A0, the theoretical indicator for microbial lethality by thermal disinfection, and to assess whether the cabinet washer could pass the minimum quality standard of A0 = 600. Temperature curves showed an A0 > 1000 consistently across all processed equipment during thermal disinfection. These data suggest that, when sterilization is not required, a cabinet washer with thermal disinfection could replace an autoclave and reduce environmental and financial waste.

Development and Testing of a Sedation Scale for Use in Rabbits (Oryctolagus cuniculus)

In biomedical research, rabbits are commonly sedated to facilitate a variety of procedures. Developing a sedation assessment scale enables standardization of levels of sedation and comparisons of sedation protocols, and may help in predicting sedation level requirements for different procedures. The goal of this study was to develop a rabbit sedation assessment scale using a psychometric approach. We hypothesized that the sedation scale would have construct validity, good internal consistency, and reliability. In a prospective, randomized, blinded study design, 15 (8 females, 7 males) healthy 1-y-old New Zealand white rabbits received 3 intramuscular treatments: midazolam (0.5 mg/kg; n = 6); midazolam (1.5 mg/kg)–ketamine (5 mg/kg; n = 7); and alfaxalone (4 mg/kg)–dexmedetomidine (0.1 mg/kg)–midazolam (0.2 mg/kg; n = 3). One rabbit received 2 treatments. A sedation scale was developed by using psychometric methods, with assessment performed by 6 independent raters who were blind to treatment. Final sedation scale items included posture, palpebral reflex, orbital tightening, lateral recumbency, loss of righting reflex, supraglottic airway device placement, toe pinch, and general appearance. The scale showed construct validity, good to very good interrater reliability for individual items (6 raters; intraclass correlation coefficient, 0.671 to 0.940), very good intrarater reliability (5 raters; intraclass correlation coefficient, 0.951 to 0.987), and excellent internal consistency (Cronbach α, 0.947). The sedation scale performed well under the conditions tested, suggesting that it can be applied in a wider range of settings (different populations, raters, sedation protocols).