A pilot study on alternative blood sampling methods in pigs

The collection of blood samples allows the monitoring of animal health and can be achieved by puncture or catheterization of specific veins. However, this process raises ethical concerns regarding animal welfare. As an alternative to traditional invasive blood collection methods, we tested the use of kissing bugs (Dipetalogaster maxima, a blood-sucking insect) and devices derived from human medicine, such as vascular imaging (VeinViewer^®) and prick lancets used for finger pricking. These methods were compared against the catheter collection method, which is considered the gold standard method for repeated blood sampling. The blood collection methods were tested in six female Large White pigs at four time points. Methods were compared for ease of collection, animal stress indicators, and obtained concentrations of plasma cortisol and glucose.

Among the methods, the catheter and insects were the least stressful, followed by the prick lancet, and the VeinViewer^®. The VeinViewer^® was the most stressful, mainly because the pig had to be restrained with a snout rope. According to the operators, the VeinViewer^® and prick lancet sampling were the most difficult methods to perform, whereas catheter and kissing bug sampling were easier. However, kissing bug sampling took up to 50 min compared to other methods (2-3 min). The method of sampling has a significant effect on glucose concentrations, with lower concentrations obtained with prick lancet (6.1 mg/dL, p < 0.05) and kissing bugs (73.8 mg/dL, p > 0.05) compared to the catheter method (93.2 mg/dL) and the VeinViewer^® (94.7 mg/dL). Glucose concentrations obtained by catheter were significantly correlated with those obtained by the VeinViewer^® (r = 0.47) or kissing bugs (r = 0.54). Differences in cortisol levels were less pronounced, with only the prick lancet method showing lower concentrations (2.9 ng/dL, p < 0.05) compared to the other methods (catheter 19.3 ng/dL, kissing bugs 20.8 ng/dL, and VeinViewer^® 20.4 ng/dL). Significant Spearman's correlations were observed between cortisol concentration of samples obtained by catheter and VeinViewer^® (r = 0.64) or prick lancet (r = 0.52).

These findings underscore the reliability of catheterization as the gold standard, although the prick lancet appears promising to reduce pig's stress. However, the method could be further refined, both in terms of animal acceptability and especially analytical procedures.