Ear vein

Technique

Pigs are intelligent and can be trained to accept handling and restraint. They will remember receiving a reward (e.g. food treat) after the procedure, which can make them easier to handle on subsequent occasions.

Venepuncture from the marginal ear veins of pigs is suitable for single and repeat sampling of small volumes (<1 ml). The technique can be used with all breeds, although the ear veins of minipigs are small and can collapse if too much vacuum is applied when withdrawing the sample.

Images of marginal ear vein sampling and other techniques for blood sampling from pigs are available on the website of the Norwegian School of Veterinary Science.

The pig needs to be restrained for sampling and this can be stressful. Stress can be minimised by training the animal to cooperate with the procedure and by conducting it in a quiet environment, if possible. Sedation of the pig should be considered, particularly when withdrawing larger blood volumes. Large pigs can be bled whilst standing and restrained by a snout rope. Minipigs and small pigs can be held across the lap or against the body.

The technique should be carried out aseptically. To limit injury and bruising at the sampling site no more than three attempts should be made. Local anaesthetic cream (e.g. EMLA cream) can be applied to the site 30 minutes prior to blood sampling. 

The ear should be warmed in order to dilate the vessel. This can be done by gently stroking and applying a swab soaked with warm water and then drying the area. Alternatively, an alcohol swab can be used, but it is important to note that the evaporation of alcohol will cool the surface of the ear.

The vein is occluded at the base of the lateral surface of the ear. The needle is slid towards the base of the ear. When the vein has been punctured, the emerging blood can be collected directly by capillary action into appropriate tubes. Serial blood samples can be taken by moving towards the base of the ear on the same vein and by alternating ears. Blood flow should be stopped, before the animal is retuned to its pen, by applying finger pressure to the soft tissue. A finger should be placed at the blood sampling site for approximately two minutes.

Up to eight samples can be collected in any 24-hour period, taking into account limits on sample volume.

Summary

Number of samples Up to eight in any 24-hour period.
Sample volume 1 - 3 ml, depending on the size of the pig.
Equipment 21G - 23G needle, depending on the size of the pig.
Staff resource Resource requirements will vary depending on the size of the animal and the amount of training and handling received. A minimum of two people will be needed: one to restrain the pig and the other to take the blood sample. 
Adverse effects
  • Bruising
  • Haemorrhage
  • Infection
Other Pigs should be trained to cooperate with blood sampling in order to minimise stress. A reward (e.g. food treat) should be given, where possible, after the procedure.

Resources and references

Ear vein sampling in other animals

This technique is only appropriate for use in the pig

All blood sampling techniques in the pig

Click here for information on cranial vena cava sampling in the pig