A Comparison of Blood Collection Techniques in Mice and their Effects on Welfare

Venipuncture Site Influences Blood-drop Volume in C57BL/6 Mice

Many experiments require the collection of serial blood samples from mice. However, the size of mice limits the volume of blood that can be safely collected as a survival procedure. In IACUC protocols, investigators may report the amount of blood they collect from mice as a number of drops. Many institutions, including ours, use an anecdotal conversion factor (1drop of mouse blood = 25μL) to ensure that blood-collection volumes are compliant with institutional guidelines. To our knowledge, previous work has not experimentally determined the volume of a drop of mouse blood. In this 10-wk crossover experiment, 2 phlebotomists bled 30 C57BL/6J mice from 3 sites (facial, saphenous, and tail) using one or 2 different needle gauge sizes per site. Male and female mice were weighed weekly and divided among 5 groups (n = 6): left and right tail vein, left and right saphenous vein, and facial vein. A single blood drop from each site was weighed, and the volume of each drop was calculated using the average blood density determined from 8 mice terminally bled at the end of the study. Venipuncture site and side significantly influenced blood-drop weight and thus calculated volume. Facial vein puncture produced the largest drop volume (mean: 21.7μL), followed by the saphenous vein (mean: 9.97μL) and tail vein (mean: 4.96μL). Collection from the facial vein was associated with more hemorrhage and morbidity. Left-sided venipuncture was associated with slightly larger-volume blood drops, though the effect size of side was small. The results of this study may be useful in more accurately estimating blood loss via conversion of drops to volume. Our data indicate that blood collection from saphenous and tail veins minimizes blood loss relative to facial vein puncture and may optimize both serial collection of small-volume blood samples and animal welfare.

Comparison of Novel and Traditional Bleeding Techniques in Neonatal and Juvenile Mice

Blood collection is frequently used for neonatal and juvenile mice in toxicology, developmental, and immunology studies and is often a terminal procedure. However, the use of nonterminal blood collection techniques, including the submandibular and the submental collection techniques described for adult mice, may offer opportunities to reduce animal numbers and refine current methods. The use of the submental technique has not been described for neonatal or juvenile mice. In this study, we compared the submental and submandibular blood collection techniques to determine their suitability for use in neonatal and juvenile mice. Male and female CD1 mice, ages 7, 14, 21, and 28 d, were randomized by sex into submental (n = 16), submandibular (n = 16), or control (n = 8) groups. Each mouse was weighed, bled per its assigned group (or only restrained in the case of control mice), and then decapitated without anesthesia for terminal blood collection. Blood collection volume and corticosterone concentrations were measured. The 2 methods showed significant differences in the volume of blood collected at ages 14 and 28, with the submandibular technique yielding significantly higher volumes. No significant differences were detected in corticosterone levels between the 2 techniques based on age or sex. A subset of mice (n = 8, 2 per age group) were bled via submental or submandibular technique and were evaluated 48 h later for gross and histopathologic evidence of trauma. Seven of the 8 mice showed expected inflammation and healing at the collection sites, with 4 mice having embedded strands of fur in the tissue. These data indicate that the submental blood collection is a viable method for nonterminal blood collection method in neonatal and juvenile mice, especially when smaller amounts of blood are needed.

Perspectives of FTIR as Promising Tool for Pathogen Diagnosis, Sanitary and Welfare Monitoring in Animal Experimentation Models: A Review Based on Pertinent Literature

Currently, there is a wide application in the literature of the use of the Fourier Transform Infrared Spectroscopy (FTIR) technique. This basic tool has also proven to be efficient for detecting molecules associated with hosts and pathogens in infections, as well as other molecules present in humans and animals' biological samples. However, there is a crisis in science data reproducibility. This crisis can also be observed in data from experimental animal models (EAMs). When it comes to rodents, a major challenge is to carry out sanitary monitoring, which is currently expensive and requires a large volume of biological samples, generating ethical, legal, and psychological conflicts for professionals and researchers. We carried out a survey of data from the relevant literature on the use of this technique in different diagnostic protocols and combined the data with the aim of presenting the technique as a promising tool for use in EAM. Since FTIR can detect molecules associated with different diseases and has advantages such as the low volume of samples required, low cost, sustainability, and provides diagnostic tests with high specificity and sensitivity, we believe that the technique is highly promising for the sanitary and stress and the detection of molecules of interest of infectious or non-infectious origin.

Acclimation and Blood Sampling: Effects on Stress Markers in C57Bl/6J Mice

Blood sampling in rodents is common practice in scientific studies. Some of the refined methods widely used are the puncture of the saphenous vein or tail vein, or even tail docking. The handling needs of these different blood sampling methods are different and can directly affect stress, increasing the variability of the study. Moreover, there is less aversion and stress if the animal is accustomed to the environment, handling and technique. Therefore, our study aimed to assess the influence of these three blood sampling techniques (saphenous puncture, tail vein puncture and tail vein docking) and the use of previous acclimation on different indicators of animal stress, assessing blood glucose concentrations and faecal corticosterone metabolites (FCMs). Twenty-four young adult male and female C57Bl6/J mice were divided in three groups by sampling method: tail docking (TD), saphenous vein puncture (SV) and caudal vein puncture (CV) groups. All mice were studied with and without acclimation, which was performed during 9 consecutive days. The results showed that both males and females present very similar responses to the different handling and sampling methods without significant differences. Nevertheless, acclimation in all sampling methods decreased glucose and FCM levels significantly. The method that obtained the lowest glucose and FCM levels with significance was saphenous vein puncture. Therefore, we can say that it causes less stress when performing prior acclimation, even when this involves greater handling of the animal. Our results contribute to refinement within the 3R concept and could serve researchers to programme and select a good handling technique and a welfare-friendly blood sampling method for their experiments.

Post Mortem Study on the Effects of Routine Handling and Manipulation of Laboratory Mice

Routine handling and manipulation of laboratory mice are integral components of most preclinical studies. Any type of handling and manipulation may cause stress and result in physical harm to mice, potentially leading to unintended consequences of experimental outcomes. Nevertheless, the pathological effects of these interventions are poorly documented and assumed to have a negligible effect on experimental variables. In that context, we provide a comprehensive post mortem overview of the main pathological changes associated with routine interventions (i.e., restraint, blood drawing, and intraperitoneal injections) of laboratory mice with an emphasis on presumed traumatic osteoarticular lesions. A total of 1000 mice from various studies were included, with 864 animals being heavily manipulated and 136 being handled for routine husbandry procedures only. The most common lesions observed were associated with blood collection or intraperitoneal injections, as well as a series of traumatic osteoarticular lesions likely resulting from restraint. Osteoarticular lesions were found in 62 animals (61 heavily manipulated; 1 unmanipulated) with rib fractures and avulsion of the dens of the axis being over-represented. Histopathology and micro-CT confirmed the traumatic nature of the rib fractures. While these lesions might be unavoidable if mice are manipulated according to the current standards, intentional training of research personnel on appropriate mouse handling and restraint techniques could help reduce their frequency and the impact on animal wellbeing as well as study reproducibility.