Which blood collection method is least likely to cause discomfort in mice and rats?

Saphenous vein collection is considered the blood collection method that is least likely to cause discomfort in mice and rats due to several factors. This method involves accessing the saphenous vein, which is located on the lateral side of the hind leg, and it allows for relatively quick and easy blood collection. Additionally, this method can be performed while the animal is restrained in a manner that minimizes stress, making it a more humane option.

Saphenous vein collection typically causes less trauma compared to more invasive methods, leading to decreased discomfort for the animal. The procedure can often be done without the need for general anesthesia, making it a practical choice in many research settings.

In contrast, methods such as heart puncture, orbital sinus collection, and tail vein collection can lead to greater stress and discomfort. Heart puncture is invasive and can cause significant distress due to the potential for pain and the need for precise technique. Orbital sinus collection may also induce discomfort, as it requires access to a sensitive area and can result in irritation or pain. Tail vein collection, while common, may still cause discomfort, especially if the tail is manipulated or if multiple attempts are required.

Overall, the saphenous vein collection method stands out for its balance of