Light is an extrinsic factor that exerts widespread influence on the regulation of circadian, physiologic, hormonal, metabolic, and behavioral systems of all animals, including those used in research. These wide-ranging biologic effects of light are mediated by distinct photoreceptors, the melanopsin-containing intrinsically photosensitive retinal ganglion cells of the nonvisual system, which interact with the rods and cones of the conventional visual system. Here, we review the nature of light and circadian rhythms, current industry practices and standards, and our present understanding of the neurophysiology of the visual and nonvisual systems. We also consider the implications of this extrinsic factor for vivarium measurement, production, and technological application of light, and provide simple recommendations on artificial lighting for use by regulatory authorities, lighting manufacturers, designers, engineers, researchers, and research animal care staff that ensure best practices for optimizing animal health and wellbeing and, ultimately, improving scientific outcomes.

Evidence showing a relationship between the mouse gut microbiome and properties such as phenotype and reaction to therapeutic agents and other treatments has increased significantly over the past 20 to 30 y. Recent concerns regarding the reproducibility of animal experiments have underscored the importance of understanding this relationship and how differences in husbandry practices can affect the gut microbiome. The current study focuses on effects of different barrier practices in 2 barrier facilities at the same institution on the fecal microbiome of breeding C57Bl/6J mice. Ten female and 10 male C57Bl/6J mice were obtained in one shipment from Jackson Laboratories and were housed under different barrier conditions upon arrival. Fecal samples were collected on arrival and periodically thereafter and were sent to TransnetYX for microbiome analysis. Mice used for collection of feces were housed as breeding pairs, with a total of 5 breeding pairs per barrier. An additional fecal sample was collected from these mice at 8 wk after arrival. One F1 female and one F1 male from each breeding cage were housed as brother-sister breeding pairs and a fecal sample was collected from them at 8 wk of age. Brother-sister breeding colonies were continued through F3, with fecal samples for microbiome analysis were collected from each generation at 8 wk of age. Breeding colonies in the 2 barriers showed differences in relative abundance, α -diversity, and β -diversity. Our data indicate that differences in barrier husbandry practices, including the use of autoclaved cages, the degree of restricted access, feed treatment practices, and water provision practices, can affect fecal microbiome divergence in both the parental and filial generations of different breeding colonies. To our knowledge, this is the first study to examine the effect of barrier husbandry practices on the microbiome of breeding colonies through the F3 generation.

Insects are potential disease vectors for research animals. Therefore, implementing an effective pest control program is an essential component of any animal care and use program. The Guide for the Care and Use of Laboratory Animals emphasizes the humane use of traps; however, insect traps commonly use glue that can entrap escaped research mice, leading to their potential distress and injury. This situation is challenging for research facilities attempting to identify insect populations. In an effort to improve pest control in animal facilities, we sought to characterize the behavioral interactions of mice with common vermin traps. Three experiments using different combinations of traps (glue trap, live mouse trap with a clear viewing window, and live mouse trap with a red-tinted viewing window) were used in multiple behavioral testing arenas to address these questions. Experiments 1 and 2 were performed in a small arena, and Experiment 3 was performed in a simulated mouse housing room. Dependent measures included exploration of the test environment, grooming behavior, time spent near each trap, and latency to capture. Results indicate that mice were captured significantly more quickly by live traps than by glue traps, and were far more likely to enter a live trap as compared with a glue trap. Mice did not appear to differentiate between clear or red-tinted window live traps. Taken together, the results indicate that deploying both a live trap and a glue trap will allow humane capture of escaped mice yet will also capture insects in the same environment.

Sanitation guidelines for animal research facilities state that disinfection is achieved by application of high-temperature water (143 to 180 °F [62 to 82 °C]) or detergents and disinfectants. However, these guidelines are based on requirements for pasteurization, which may be unnecessarily stringent for the sanitation of nonfood items and do not address the theoretical sanitation potential of water at temperatures below 143 °F (62 °C). Recent literature indicates that water temperatures below 143 °F (62 °C) can also provide effective sanitation. In this study, we compared cagewash cycles at low (100 °F [38 °C] and 120 °F [49 °C]) and high (standard) (180 °F [82 °C]) temperatures and evaluated sanitation efficacy by using ATP swabs and RODAC plates. Low-temperature loads were washed either with or without prior treatment of a chemical disinfectant (10% bleach). The 100 °F (38 °C) cycle was not sufficient for sanitization without bleach pretreatment. However, the 120 °F (49 °C) cycle effectively sanitized cages without bleach pretreatment. Validation of effective sanitation at a lower water temperature (120 °F [49 °C]) can improve cagewash logistics and reduce costs as compared with standard (180 °F [82 °C]) high-temperature cycles.

Myocoptes musculinus is a common ectoparasite of wild mice and is occasionally found on research mice. Infestations of research mice are often subclinical but can cause severe dermatitis. Perhaps more importantly, infestations can cause immunologic reactions that may alter research outcomes, and most animal research facilities strive to prevent or eliminate mites from their mouse colonies. M. musculinus infestations are currently detected by using microscopic evaluation of the fur and skin and PCR assays of pelt swabs targeting the rRNA genes of this mite. In our facility, we encountered multiple, false-positive 18S rRNA PCR results from a closed mouse colony. We could not identify the source of the false positives even after performing PCR analysis of other Myocoptes gene targets using assays developed from the few other target genomic sequences available for M. musculinus or Myocoptes japonensis in public databases. This situation highlighted the limited genetic resources available for development of diagnostic tests specific for this ectoparasite. To expand the available genetic resources, we generated a metagenome of M. musculinus derived by sequencing from fur plucks of an infected mouse. We also determined the completeness of this metagenome and compared it with those of related mites.

Tens of thousands of rodents are used each year in Rodent Health Monitoring programs. However, Environment Health Monitoring (EHM) could replace sentinel rodent use while maintaining or even improving diagnostic quality. Despite its advantages, widespread implementation of EHM appears to be relatively low. To better understand EHM's prevalence and factors influencing its use, we surveyed research animal professionals. Our hypotheses were (1) EHM prevalence would be low and (2) EHM use would be associated with beliefs and knowledge about EHM. Participants were recruited via online promotion. A total of 158 individuals completed a mixed-methods survey about current practices, beliefs, and knowledge about EHM. Qualitative data were coded using thematic analysis and analyzed using generalized linear models. Results showed that current EHM implementation was low; only 11% of institutions used EHM exclusively. Across the 111 institutions surveyed, over 20,000 soiled bedding sentinels were used each year. However, most participants believed EHM to be advantageous in replacing sentinel animals (78% of participants). Some participants believed EHM could save time (31%), cost less (27%), and be highly accurate (15%). Conversely, some participants believed EHM would be difficult to use due to their current caging type (40%), higher costs (21%), lower accuracy (16%), and personnel attitudes/expertise (14%). Overall, respondents with higher planned EHM use also had more positive attitudes, norms, and control of EHM. We also identified several factors that could promote the implementation of EHM. Communication efforts should emphasize that EHM is compatible with various types of caging, can provide cost savings, has high accuracy, and is consistent with the 3Rs as a replacement. Efforts should also focus on improving attitudes, encouraging peers, and providing resources to facilitate implementation. Implementation in just the surveyed institutions could eliminate the need for well over 20,000 rodents each year, consistent with 3Rs goals.

Meloxicam is a nonsteroidal anti-inflammatory analgesic drug that is often used in mice. However, doses of 1 to 5 mg/kg given twice daily were recently reported to provide inadequate analgesia. Some studies suggest that doses of up to 20 mg/kg may be necessary for adequate pain management. We investigated the analgesia provided by a high-dose of meloxicam in female CD1 mice. Pharmacokinetic analyses demonstrated that a subcutaneous injection of 10 mg/kg or 20 mg/kg of meloxicam produced therapeutic plasma concentrations for at least 12 h. Ovariectomies via ventral laparotomy were performed to assess analgesic efficacy. Mice were treated immediately before surgery with a high-dose of 10 mg/kg, a low-dose of 2.5 mg/kg, or saline, followed by every 12 h for 36 h. At 3, 6, 12, 24, and 48 h after surgery, mice were assessed for pain based on the following behaviors: distance traveled, time mobile, grooming, rearing, hunched posture, orbital tightening, and von Frey. Initially, some mice received a 20-mg/kg loading dose followed by 10 mg/kg every 12 h. This regimen caused severe morbidity and mortality in 2 mice. Subsequently, this regimen was abandoned, and mice assigned to the high-dose group received 10 mg/kg every 12 h. Mice that received the 10-mg/kg dose after surgery showed less orbital tightening between 3 to 6 h and reduced frequency of hunched posture for 48 h compared with mice that received either the low-dose or saline. However, mice were significantly less mobile for 6 to 12 h after surgery regardless of treatment. These data indicate that a meloxicam dose of 10 mg/kg every 12 h provides better analgesia than a 2.5-mg/kg dose but does not completely alleviate pain.

The goal of this study was to evaluate the effect of a human observer on Rabbit Grimace Scale (RbtGS) scores. The study scored video footage taken of 28 rabbits before and after orthopedic surgery, as follows: 24 h before surgery ( baseline), 1 h after surgery ( pain), 3 h after analgesia administration ( analgesia), and 24 h after surgery ( 24h) in the presence and absence of an observer. Videos were assessed twice in random order by 3 evaluators who were blind to the collection time and the presence or absence of an observer. Responses to pain and analgesia were evaluated by comparing the 4 time points using the Friedman test, followed by the Dunn test. The influence of the presence or absence of the observer at each time point was evaluated using the Wilcoxon test. Intra- and interrater reliabilities were estimated using the intraclass correlation coefficient. The scale was responsive to pain, as the scores increased after surgery and had decreased by 24 h after surgery. The presence of the observer reduced significantly the RbtGS scores (median and range) at pain (present, 0.75, 0 to 1.75; absent, 1, 0 to 2) and increased the scores at baseline (present, 0.2, 0 to 2; absent, 0, 0 to 2) and 24h after surgery (present, 0.33, 0 to 1.75; absent, 0.2, 0 to 1.5). The intrarater reliability was good (0.69) to very good (0.82) and interrater reliability was moderate (0.49) to good (0.67). Thus, the RbtGS appeared to detect pain when scored from video footage of rabbits before and after orthopedic surgery. In the presence of the observer, the pain scores were underestimated at the time considered to be associated with the greatest pain and overestimated at the times of little or no pain.

This study investigated whether the use of commercially available diet gels prevented the postoperative weight loss associated with major survival surgery in mice. C57BL/6 mice were divided into 3 groups ( n = 9 per group) that received moistened chow pellets alone or with one of 2 commercially available diet gels. Mice began receiving the test diets 3 d before surgery (baseline) and were weighed daily for 7 d after surgery. On day 0, mice underwent ventral midline laparotomy, during which the intestines were manipulated for 2 min and a segment of jejunum was briefly clamped. Compared with the baseline value for the same group, body weights for the mice that received moistened chow only were significantly lower on all postoperative days (days 1 through 7). In contrast, body weights of mice that received both moistened chow and diet gel differed from baseline only on days 2 and 3 for one product and were never different from baseline for the other product. This study indicates that the combination of diet gel and moistened chow prevented or mitigated postoperative weight loss after a laparotomy procedure in mice.

The submental route is an option for nonterminal and serial blood collection in mice. This study compared the submental route to the maxillary route (also referred to as the submandibular route). The study used male CD1 and C57BL/6 strains of mice in 2 age groups: 8 and 19 wk. To simulate repeated toxicokinetic blood collection, blood was collected from each mouse at 1 and 24-h on Study Day 1, and at 1, 4 and 24 h on Study Day 16. Food consumption, body weights, and clinical observations were assessed daily. No apparent differences were found between the 2 blood collection sites in terms of either food consumption or body weight. Mice bled via the submental route showed fewer adverse clinical effects than did mice bled via the maxillary route. Clinical pathology showed no differences between the 2 methods. In addition, 7 trained technicians, who were inexperienced with the 2 bleeding methods prior to these evaluations, were surveyed to gain insights into expectations and overall experience of using the 2 routes. All 7 technicians preferred the submental route to the maxillary route. Furthermore, the average time needed to become proficient in submental blood collection (1.6 d) was less than that required to become proficient in maxillary blood collection (2.6 d). The qualitative aspects of this study, combined with fewer adverse clinical events, suggest ways to improve both animal and staff welfare. Our findings suggest that the submental route is safe, effective, and easier than the maxillary route for nonterminal serial blood collection in mice.