Blood sampling: Pig
Approaches for sampling blood in the pig, covering non-surgical and surgical techniques.
On this page
General principles
You should read the general principles of blood sampling page before attempting any blood sampling procedure.
Ear vein (non-surgical)
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 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 | Up to 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 |
|
| 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
- Xu J et al. (2020). Blood collection from the porcine ear using a jet injector, 42nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Montreal (Canada), 20-24 July 2020. doi: 10.1109/EMBC44109.2020.9175421
- Swindle MM (2010). Blood collection in swine.
- Diehl KH et al. (2001). A good practice guide to the administration of substances and removal of blood, including routes and volumes. Journal of Applied Toxicology 21(1) 15-23. doi: 10.1002/jat.727
- O'Malley CI et al (2022). Refining restraint techniques for research pigs through habituation. Frontiers in Veterinary Science. 23(9):1016414. doi: 10.3389/fvets.2022.1016414
External jugular vein (non-surgical)
Technique
Venepuncture from the external jugular vein is the most common route of blood collection in the pig due to the comparative ease of the technique and the capacity to draw repeat samples of blood at relatively large volumes. While greater volumes can be taken, typically less than 20ml of blood is collected from the animal at any one time due to the stress of handling and restraint the procedure can cause.
Images of jugular 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.
The procedure 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 external jugular vein can be accessed in the jugular furrow which is visible after extending the neck and retracting the foreleg caudally. Depending on the size of the pig, a 19-21G needle should be inserted perpendicular to the skin at the deepest point of the jugular groove found between the medial sternocephalic and lateral brachiocephalic muscles. It is vital that the animal is held firmly while the procedure is carried out, as struggling poses a high risk of damage to the jugular vein. Use of a vacuum tube to collect samples can reduce the risk of injury to the animal and operator by limiting the level of manipulation required to draw blood. Be aware that the needles used in vacuum tubes are typically too short to reach the jugular vein in large sows. When sampling from larger animals, ensure the needle is inserted to its full length and gently compress the adipose tissue above the vein to ensure successful venepuncture.
Blood flow should be stopped by applying finger pressure on a gauze pad or other absorbent material placed on the blood sampling site for between 30 seconds and two minutes. The pig should not be returned to its pen until the blood has stopped flowing.
Summary
| Number of samples | Up to eight in any 24-hour period dependent on volume |
| Sample volume | 20 ml, depending on the size of pig. A vacuum tube system can be used to collect smaller samples (e.g. 3 ml). |
| Equipment | 19G-21G needles for pigs and 20-21G needles for minipigs (1" long for minipigs/young pigs and 2" long for larger pigs). |
| Staff resource | Four people are required, three to hold the pig in position (head, stifle and front legs) and one person to take the blood sample. Two to three people are sufficient for minipigs, pigs that are used to the procedure or pigs in slings. |
| Adverse effects |
|
| 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. When sampling from large pigs, correct positioning of the snout rope is important to reduce the potential for injury to the mouth and undue pressure on sensitive nasal tissues. |
Resources and references
- Swindle MM (2010). Blood collection in swine.
- Diehl KH et al. (2001). A good practice guide to the administration of substances and removal of blood, including routes and volumes. Journal of Applied Toxicology 21(1): 15-23. doi: 10.1002/jat.727
- O'Malley CI et al (2022). Refining restraint techniques for research pigs through habituation. Frontiers in Veterinary Science. 23(9):1016414. doi: 10.3389/fvets.2022.1016414
Cranial vena cava (non-surgical)
Technique
Sampling from the cranial vena cava is suitable for all breeds commonly used, including the large white and minipig. It is the best technique for taking a single blood sample from a pig at any one time. It can be used to obtain a relatively large volume of blood (e.g. >20 ml). For smaller volumes, the peripheral ear veins of the pig can be used, or saphenous cannulation when repeat sampling is required. Sampling from the cranial vena cava is not suitable for taking multiple samples as repeated sampling from this area will result in hematoma or blood clot formation in the thoracic inlet. Multiple samples can be collected via the jugular vein (see below) or use of a catheter (either surgical or percutaneous).
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.
The technique should be carried out aseptically. To limit injury and bruising at the sampling site no more than three attempts should be made. Small pigs should be held in a supine position; head and neck straightened out and front limbs drawn backwards. An adjustable V-shaped cushioned restrainer, or sling, can help hold the animal in position. Large pigs (>15kg) can be bled whilst standing (a snout rope is positioned behind the canine teeth and the neck lifted upwards). If it is necessary to place the animal in dorsal recumbency, this should be for the minimum length of time possible; five minutes should be sufficient time to collect a sample. Inhaled anaesthesia may be used if the animal needs to be restrained for longer (up to 20 minutes).
The needle is inserted at a 45o angle into the vena cava approximately 1" (0.5 1" for minipigs) cranial to the sternum a little lateral and to the right of the midline. Blood flow should be stopped by applying finger pressure on a gauze pad or other absorbent material placed on the blood sampling site for between 30 seconds and two minutes. The pig should not be returned to its pen until the blood has stopped flowing.
Summary
| Number of samples | Usually one in seven days. |
| Sample volume | 5-30 ml, depending on the size of pig. A vacutainer system can be used to collect smaller samples (e.g. 3 ml). |
| Equipment | 19G-21G needles for pigs and 20-21G needles for minipigs (1" long for minipigs/young pigs and 2" long for larger/older pigs). |
| Staff resource | Four people are required, three to hold the pig in position (head, stifle and front legs) and one person to take the blood sample. Two to three people are sufficient for minipigs, pigs that are used to the procedure or pigs in slings. |
| Adverse effects |
|
| 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. When sampling from large pigs, correct positioning of the snout rope is important to reduce the potential for injury to the mouth and undue pressure on sensitive nasal tissues. |
Resources and references
- Diehl KH et al. (2001). A good practice guide to the administration of substances and removal of blood, including routes and volumes. Journal of Applied Toxicology 21(1): 15-23. doi: 10.1002/jat.727
- Swindle MM (2010). Blood collection in swine.
- O'Malley CI et al (2022). Refining restraint techniques for research pigs through habituation. Frontiers in Veterinary Science. 23(9):1016414. doi: 10.3389/fvets.2022.1016414
Saphenous cannulation (surgical)
Technique
Cannulation of the saphenous veins of pigs is suitable for repeat sampling of small volumes (<2 ml). The technique can be used as an alternative to repeat sampling of the ear veins of minipigs which are small and can collapse if too much vacuum is applied when withdrawing the sample. Cannulation can also be used to administer as well as withdraw fluids.
For cannulation surgery, pigs need to be sedated or anaesthetised. Fasting of the pig is required before anaesthesia, and removal of the bedding overnight is recommended as pigs may consume bedding if hungry. To provide warmth to compensate for the removal of the bedding, heat lamps may be provided. Stress can be minimised by training the animal to accept the anaesthetic mask or face cone (and any restraint or lifting).
This technique should be carried out aseptically, with the hind legs clipped and cleaned around the area to be cannulated. The hind legs should be warmed in order to dilate the vessel. A glove filled with warm water and tied off can be used as a simple means to dilate the vessel. A tourniquet can also be used also to help dilate the vessel.
A VeinViewer® or similar product may also be used. This piece of equipment uses near-infrared light (which is absorbed by blood and reflected by surrounding tissue) to show the position of the veins to aid good placement of the cannula.
The vein is occluded below the area of insertion of the cannula. A small incision is made with a scalpel above the vein, this aids in placing of the cannula as pig skin is very tough and the cannula can be damaged (kinked) without this. The cannula is slid up the vein until blood is seen within the cannula. At this point, the guide needle should be withdrawn carefully and the cannula can then be positioned in the vessel without damaging it. The cannula is then capped and 200µl of lock solution (e.g. heparin) administered into the cannula to maintain patency. The cannula can then be secured in place with adhesive tape. The pig can then be recovered in home pen or sling.
All subsequent blood samples can be taken from the cannula, and patency maintained with the administration of locking solution each time a sample is taken. Pigs can be trained to sit in slings for sampling or gently restrained. The cannula should be checked after sampling before the animal is returned to its pen and during routine checks.
Multiple samples may be collected, taking into account project licence and sample volume limits.
Summary
| Number of samples | Multiple in any 24-hour period. |
| Sample volume | Up to 1-3 ml, depending on the size of the pig. |
| Equipment | 18G cannula |
| 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 to restrain the pig, anaesthetize, cannulate and take the blood sample. |
| Adverse effects |
|
| 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
References
- Schmidt W et al. (1988). A central venous catheter for long-term studies on drug effects and pharmacokinetics in Munich minipigs. European Journal of Drug Metabolism and Pharmacokinetics 13(2): 143-7. doi: 10.1007/BF03191316
- Diehl KH et al. (2001). A good practice guide to the administration of substances and removal of blood, including routes and volumes. Journal of Applied Toxicology 21(1): 15-23. doi: 10.1002/jat.727Ettrup KS et al. (2011). Basic surgical techniques in the Göttingen minipig: Intubation, bladder catheterization, femoral vessel catheterization, and transcardial perfusion. Journal of Visualized Experiments: JoVE (52): 2652. doi: 10.3791/2652
- Usvald D et al. (2008). Permanent jugular catheterization in miniature pig: treatment, clinical and pathological observations. Veterinarni Medicina 53(7): 365-72. doi:10.17221/1992-VETMED
- Pinkernelle J et al. (2009). Sonographically guided placement of intravenous catheters in minipigs. Lab Animal 38(7): 241-5. doi: 10.1038/laban0709-241
- Pluschke AM et al. (2017). An updated method for the jugular catheterization of grower pigs for repeated blood sampling following an oral glucose tolerance test. Laboratory Animals 51(4):397-404. doi: 10.1177/0023677216682772
- Klein P et al. (2019). The method of long-term catheterization of the vena jugularis in pigs. Journal of Pharmacological and Toxicological Methods 98: 10658. doi: 10.1016/j.vascn.2019.106584
- Furbeyre H and Labussiere E (2020). A minimally invasive catheterization of the external jugular vein in suckling piglets using ultrasound guidance. PLoS ONE 15(10): e0241444. doi: 10.1371/journal.pone.0241444
You should read the general principles of blood sampling page before attempting any blood sampling procedure.
