Cage-Side Blood Collections from the Ear Can Be Used for Hematological Evaluations in Japanese Macaques (Macaca fuscata)

Japanese macaques (Macaca fuscata) are used in biomedical research where frequent, small-volume blood sampling for monitoring the animal's health may be required. Femoral blood collected under anesthesia is the standard for obtaining CBC analyses from nonhuman primates to assess their health. However, anesthetizing animals to obtain these collections may not be ideal due to adverse impacts of frequent anesthesia. Cage-side blood sampling from the pinna of the ear is a convenient and less invasive method for blood collection without anesthesia. However, it is unknown whether hematologic parameters from blood collected from the pinna are representative of femoral blood collections. The objective of this study was to determine whether hematologic parameters obtained from blood collected from the pinna of the ear can be used as a surrogate for hematologic parameters from blood collected from the femoral vein in Japanese macaques. Ten male Japanese macaques were trained to present their pinnae for blood collections without anesthesia, after which the macaques were anesthetized for pinna and femoral blood sampling for comparison. Anesthesia, rather than blood sampling site, was responsible for statistically significant differences in leukocyte parameters between pinna and femoral blood samples. In contrast, differences in erythrocyte and platelet parameters between pinna and femoral blood were driven by the collection site, with anesthesia contributing to a lesser degree. While statistical differences were identified, the clinical relevance of these differences was minimal. Taken together, this study indicates that cage-side pinna blood samples collected from conscious Japanese macaques are different than femoral blood samples collected under anesthesia but are suitable for frequent hematologic monitoring.