Ear vein

Please read the general principles of blood sampling page before attempting any blood sampling procedure.

Technique

Venepuncture from the marginal ear veins of pigs is suitable for single and repeat sampling of small volumes (1-3 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 NORECOPA website.

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. Pigs are intelligent animals and will remember receiving a reward (e.g. food treat) after the procedure, which can make them easier to handle on subsequent occasions. Positive reinforcement training should be used where possible for all procedures from weighing to procedural work to minimise stress to technician and pig.

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. Minipigs can also be sling trained for blood collection to minimise the risk of injury to both handler and pig.

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. 

Cannulation of the ear vein may also be considered as an alternative to repeat venepuncture and multiple samples may be taken once the cannula is in place. Heparin or a suitable lock solution will need to be used to maintain patency of the cannula and so may not be suitable for all studies.

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. A latex glove filled with warm water and tied off can also be used to dilate the ear vein for blood sampling.

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 returned 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 ear vein sampling in the pig