Short communication: Impact of blood collection site and sampling protocol on plasma glucose and uric acid concentrations in wild-caught mourning doves, Zenaida macroura.

Circulating biomarkers are commonly measured by researchers to assess the health of wild animals. Previous studies of mammals have reported variations in plasma glucose concentrations between peripheral and cardiac blood samples, as well as between venous and arterial samples. To our knowledge, however, no studies have compared plasma metabolites collected from different sampling sites in wild-caught birds. Adult mourning doves of both sexes (n = 13) were captured using walk-in style funnel traps as part of a separate study. Blood samples were collected from the ulnar vein of unanesthetized birds. Following euthanasia with sodium pentobarbital (200 mg/kg, i.p.), blood samples were also collected from the cardiac left ventricle (LV). Plasma was separated from formed elements and analyzed for glucose and uric acid concentrations using commercially available kits. In contrast to mammals, there were no significant differences in glucose concentrations between sampling sites (paired t-test; p = 0.6582), and glucose concentrations from ulnar vein and cardiac LV samples were positively correlated (Spearman r = 0.7363; p = 0.0041). In contrast, ulnar vein samples had higher uric acid concentrations (paired t-test; p = 0.0007), and no correlation was observed between ulnar vein and cardiac LV samples for this metabolite (Spearman r = 0.3956; p = 0.1809). Additionally, glucose and uric acid concentrations were not significantly correlated within either the ulnar vein (Spearman r = -0.2363; p = 0.4371) or cardiac LV (Spearman r = 0.3462; p = 0.2466) samples. These findings highlight the importance of considering sampling site and condition when measuring plasma metabolites and when comparing results across studies.