Introduction
This year we would like to introduce you to “pigs as laboratory animal models”, which have led to great achievements in biomedical research. In the following sections you will learn more about different breeds, which can be grouped into two main categories: The domestic pigs and the mini pigs.
The standard breeds of domestic pigs used in research in Germany are often the German Landrace and Landrace hybrids. However, there are also minipigs, including the Göttingen Minipig, the Aachen Minipig and the Cardio Pig - three breeds that have been bred specifically to meet the requirements of biomedical research by crossing other breeds.
In the following, we have compiled information that shows why and in which areas pigs are used in research, what characteristics they have and what milestones have been achieved with pigs.
Why are pigs used in research?
Pigs have a similar anatomy and physiology to humans, which is why they can be used to make more accurate predictions about our bodies and how they function and react to different substances. Our immune system alone is about 80% similar to that of pigs. And the pig's heart in particular has many similarities in structure and size to ours. This is why pigs are often used for human cardiovascular research.
Pigs can be genetically modified using modern technologies to make them even more similar to humans. Although there are currently fewer established methods available in this area than for mice, such modifications open up promising potential applications. For example, pigs can serve as potential organ donors for transplant medicine or be used in the development and testing of new drugs and therapies. Their physiological reactions provide valuable insights into how the human body might react to certain interventions or active substances.
While the standard breeds of domestic pigs (German Landrace or Landrace hybrid) are suitable for short-term/acute trials, minipig breeds are advantageous for long-term and chronic studies. In addition to the advantages of limited growth and body weight, other characteristics can also speak in favor of mini pigs. However, the use of minipigs is limited in certain research questions. For example, in the field of xenotransplantation, animals should be chosen in which the size of the organs corresponds to that of human organs. In the case of standard breeds, it must be borne in mind that they are still in growth when a weight class comparable to that of humans is reached.
In addition, the breeding of standard breeds of domestic pigs for agricultural purposes is based on continuous selection with the aim of preserving genetic diversity, which contradicts genetic standardization in research.
In contrast to rodents, genetic standardization is not an ultimate goal for large animal models used in preclinical research. The goal of the breeding concept of large animal models is to mimic the genetic structure of non-bred populations by creating and maintaining constant genetic heterogeneity.
In which areas of biomedical research do pigs play a role?
The biomedical research areas in which pigs are chosen as model laboratory animals are:
- Surgical training: prospective surgeons are initially trained on dummies or surgical trainers in line with the 3Rs. Nevertheless, in some areas it is still necessary to train surgical procedures on pigs in order to provide full surgical training.
- Testing of medicinal products and medical devices: It is a legal requirement that newly developed medicines and therapies must be tested on animals before they can be marketed. Pigs are often used for these tests in addition to a rodent species, although a non-rodent species is always required. The similarity of pigs to humans also plays a role in the selection of such a model.
- Skin diseases: Pig skin has approximately the same thickness and composition as our own skin. Through research on pigs, we can better understand allergies, our wound healing and the skin disease psoriasis (non-contagious skin and joint disease that causes inflamed, itchy skin and dandruff) and develop antidotes.
4. Gene editing: Genetically modified pigs map human disease processes more accurately than conventional pigs or other genetically engineered animals. Using techniques such as CRISPR-Cas9, scientists can perform targeted genetic modifications to better study diseases such as Huntington's disease (a neurodegenerative disease that leads to the loss of more and more areas of the brain and thus to the loss of control of muscle movements as well as mental and cognitive functions).
Profile - Domestic pig vs. mini pigs
Domestic pig
- Adult animals can reach up to 80-90 cm shoulder height
- The weight is approx. 140-300 kg
- Sows give birth to 10-14 piglets per litter
- The gestation period is approx. 115 days
Göttingen minipig
- Adult animals can reach up to 32-38 cm (females) or 35-45 cm (males) shoulder height
- The weight is approx. 35-45 kg (females) or approx. 40-60 kg (males)
- Sows give birth to 6-7 piglets per litter
- The gestation period is 112-114 days
Aachen minipig
- Adult animals can reach up to 32-38 cm (females) or 35-45 cm (males) shoulder height
- The weight is approx. 40-50 kg (females) or approx. 40-55 kg (males)
- Sows give birth to 6-7 piglets per litter
- The gestation period is approx. 115 days
Cardio Pig
- Adult animals can reach a shoulder height of up to 50 cm (females) or 55 cm (males)
- The weight of adult animals is approx. 70-85 kg (females) or approx. 75-90 kg (males)
- Sows give birth to 6-7 piglets per litter
- No purebred animals, therefore no cardio breeding sows
Innovative pig models from Aachen:
Aachen minipig and cardio pig for biomedical research
From 2013, the “Aachen Minipig” was established in Aachen as a robust, non-specific pathogen-free pig breed with a final weight of 30-60 kg in strict compliance with the 3R principle (Refinement, Reduction, Replacement). In 2021, the slow-growing “Cardio Pig” was added, which at around 80 kg provides a model more similar to human organ dimensions. Both lines are bred in North Rhine-Westphalia and offer ideal conditions for medical and pharmacological research thanks to their stable health status and adapted body size.
The Aachen minipigs have already been successfully used in orthopaedic experiments, long-term safety tests of temperature-controlled whole-body therapies against external pathogens, as an in vivo model for investigating intracranial artery diameters, for microbiological characterization in xenotransplantation researcht.
Husbandry, dietary preferences, behavior, social structure and enrichment methods of pigs as laboratory animals
Housing conditions
- Domestic pigs with a live weight of 100 kg or more require at least 1.35 m² of space per animal. Adult mini pigs in the 30-50 kg weight range require around 0.50 m² of space per animal.
- The barn temperature is set between 15 °C and 20 °C for adult animals and between 30 °C and 36 °C for newborns.
- Lighting of at least eight hours at 80 lux or equivalent daylight is required.
- The floor must be non-slip and dry, with gap widths adapted to the age stage. Bedding such as straw, sawdust or paper is provided autoclaved to encourage burrowing and nest-building behavior and to keep it hygienic.
- Newly arrived animals remain in quarantine for two to four weeks and must have a health certificate with serology results.
- Automatic drinking systems should be checked twice a day to ensure they are working properly, as pigs can manipulate them.
- Padded recovery boxes are available for intensive medical aftercare, which allow access for infusions and oxygen.
Dietary preferences
- Pigs are omnivores with a preference for sweet foods, and the texture of the feed has a strong influence on acceptance.
- Feeding is age-appropriate in the starter, rearing, maintenance and breeding phases. Pelleted feed is preferred in laboratory husbandry, and the feed from the farm of origin is initially retained during acclimatization. Immediately after weaning, a multi-feed system with many small meals is recommended to stabilize the intestinal flora.
- Mini pigs are given energy-reduced feed with 10-14% crude fiber and 13-16% protein to counteract their tendency to obesity.
- Feed additives such as probiotics, organic acids and medium-chain fatty acids support the stability of the gastrointestinal tract.
Behavior
- Pigs exhibit pronounced burrowing, nest-building and exploratory behavior, which must be taken into account when keeping them.
- They consistently separate lying and excrement areas and avoid contact with their excrement.
- Regular showering can promote grooming and thermoregulation behavior.
- Positive training with clicker or target methods reduces anxiety and stress during handling.
Social structure
- Domestic pigs and minipigs are social animals with a fixed hierarchy and should be kept in stable groups. Individual housing is only permitted if medically indicated and must allow visual, auditory and olfactory contact with conspecifics.
- Mini pigs from SPF (specified pathogen-free) breedings are often kept individually, but also require social contact opportunities.
Enrichment and training
- Activity materials such as chains, balls and teething rings must be replaced regularly to avoid habituation. These materials must be robust, non-toxic and easy to clean; wood is usually only suitable for single use.
- Hay, straw, fruit and vegetables are hidden in feeding toys to encourage exploratory behavior. Food rewards such as corn rings or sugar cubes serve as positive reinforcers during training and help to reduce stress.
- Clicker and target training facilitates sampling, medication application and handling.
Milestones in biomedicine with pigs
For more than a century, pigs have provided us with answers to essential biological processes. In the timeline you can discover the most important groundbreaking developments and successes that have shaped biomedical research.
For the interactive version, please click here: Pigs in Biomedical Research
To download the PDF version, please click here:
Number of pigs used in research 2023
According to the latest report (2023) from the Bf3R - German Center for the Protection of Laboratory Animals at the Federal Institute for Risk Assessment, pigs account for 0.66% of the total number (approx. 1.46 million animals) of laboratory animals used in Germany in 2023. 40% of these pigs were used for translational and applied research and 32% for training to acquire, maintain or improve professional skills. 14% of the 9643 pigs were used for fundamental research and 11% for regulatory purposes and routine production. 3% of the pigs used in 2023 were used in university education.
Selected publications on research projects with pigs from NRW
RWTH Aachen
- Implementation of the Surgical Apgar Score in Laboratory Animal Science: A Showcase Pilot Study in a Porcine Model and a Review of the Literature - PubMed
- Orthotopic Kidney Auto-Transplantation in a Porcine Model Using 24 Hours Organ Preservation And Continuous Telemetry - PubMed
- A Novel Hypobaric Perfusion Method to Remove Microthrombi in Kidney Grafts with Prolonged Circulatory Arrest: A Pilot Study on a Porcine Model - PubMed
- A Proof-of-Concept Preclinical Study Using a Novel Thermal Insulation Device in a Porcine Kidney Auto-Transplantation Model - PubMed
References and further links
Efficacy of the porcine species in biomedical research
The Pig as a Model for Human Wound Healing
Importance of the pig as a human biomedical model
The role played by protozoa in causing disease
Novel therapies to treat parasitic infections
Xenotransplantation: Interview mit Univ.-Prof. Dr. med. René Tolba
First pig-to-human heart transplantation
Verwendung von Versuchstieren im Berichtsjahr 2023
Glodek P: Entstehung und züchterische Fortentwicklung; in Glodek P, Oldigs B (eds): Das Göttinger Miniaturschwein. Berlin/Hamburg, Paul Parey, 1981, pp 9–17.
Ellegaard L, Damm Jørgensen K, Klastrup S, Kornerup A, Svendsen O: Haematologic and clinical chemical values in 3 and 6 months old Göttingen minipigs. Scand J Lab Anim Sci 1995; 22: 239–248.
Acknowledgments
We would like to thank all network members who have contributed to this page “Pigs in biomedical research” from its conception to its creation.