What technique is used for blood collection in animals that lack large veins, particularly certain rodents?

The retro-orbital technique is specifically designed for blood collection in small animals, particularly rodents that may not have easily accessible large veins for venipuncture. This technique involves accessing the venous sinus located behind the eye, allowing for collection of sufficient blood volume with minimal stress to the animal.

It is especially useful for species like mice or rats, which have smaller blood volumes and veins that are difficult to access directly. By utilizing this method, technicians can efficiently obtain blood samples for various laboratory analyses, such as hematology or serology.

Other techniques mentioned may not be ideal for these particular rodents. Intraarterial methods are generally more invasive and not frequently employed for routine blood sampling in small animals. Cardiac puncture, while effective, poses greater risks and is more suitable in terminal procedures rather than routine sampling. Tail transection is also not considered an appropriate method for blood collection due to ethical concerns and the pain it would cause to the animal. Thus, retro-orbital blood collection remains the preferred choice in these cases.