Göttingen Minipigs are a well-known non-rodent species used for developmental and juvenile toxicity studies (1, 2). To ensure research quality and animal welfare, knowledge about the normal reproductive characteristics of the Göttingen Minipigs, correct handling of the sow before, during, and after farrowing, and the care of the newborn piglets is critical.
Gestation
The gestation period for Göttingen Minipigs lasts for an average of 115 days. Sows that have fewer piglets or are breeding for the first time may experience delayed farrowing. However, Göttingen Minipigs have a low rate of reproductive failure and a high success rate for both pregnancy and farrowing. On average, Göttingen Minipigs give birth to a litter of 8.1 piglets, but this number may vary depending on parity (as shown in Figure 1).
It is possible to synchronize estrus in Göttingen Minipigs, and farrowing can be induced, which allows a group of sows to farrow within a short time frame of typically 24-48 hours. Additionally, the incidence of congenital external and visceral malformations in Göttingen Minipigs is low (3).
Average number of piglets born alive (in turquoise) and stillborn (in orange) in the period 2020-2023 divided into parity at Ellegaard Göttingen Minipigs, Dalmose, Denmark.
Taking care of the sow
Pregnant sows should be transferred to the farrowing pen 7–10 days prior to the farrowing date. The farrowing pen should be designed to provide the best environment for the sow and the piglets e.g. space and opportunity for the sow to perform nest building, bars to protect the piglets from the sow, and an area with additional heat for the newborn piglets.
Socialization of the pregnant sow, for example through hand-feeding or petting/scratching before and after farrowing creates a calm and trusting environment, even when staff members are interacting with the piglets. Having the sow habituated to touching and manipulation also makes it easier to get a sense of how close to farrowing the sow is. As she nears parturition, her udder will be harder, and her teats will have milk in them.
The temperament of the sow has an impact on the piglets and their reaction to humans, and a calm sow typically will foster calm piglets. However, a certain amount of protective maternal behavior is beneficial for the sow to care for her piglets. Primiparous sows may be more nervous than more experienced breeders and it is important to respect the individual sow’s temperament in the socialization and care immediately after farrowing.
It is essential for sows to get the correct amount of feed up to farrowing, so that they have enough energy to farrow, but also to avoid problems with constipation and prolonged farrowing. Sup-optimal energy and dietary conditions may also affect milk production after farrowing. The eating habits and general condition of the sow must be observed closely, and the amount of diet should be decreased or increased accordingly. Sows with problems keeping their weight should be fed multiple small meals daily and treats (e.g. fruit, juice, yogurt) until normal body condition is regained.
The sows must have access to plenty of fresh clean water, either from a water nipple supplying a minimum of 2–4 liters per minute or from a well-attached bowl.
The ambient temperature at sow height should be 18–20°C.
Parturition
Sows usually become more restless a day or two before farrowing and start nest-building behavior. To facilitate this, it is important to provide sufficient bedding material in the pen (as shown in Picture 1).
Sow after farrowing. The provision of material for nest building not only improves the wellbeing of the sows, but also gives a good indication of imminent farrowing.
When a sow lies down in the nesting area and begins to go into labor, it is essential not to disturb her. Sows usually give birth during the night, and they usually don't need any assistance. However, if the sow has been in labor for more than two hours, and no piglets are born, take her out of the pen and walk her for 5-10 minutes in the aisle. It is good if the sow urinates while she is up and walking. The time it takes from the first piglet's birth until the last piglet and the placenta are expelled varies greatly. The sow may eat the placenta which is thus not always observable in the pen. After farrowing, the sow must be checked to confirm she is alert and interested in the piglets. A veterinary examination must be performed if there are any signs of clinical disease, depressed behavior, or refusal to nurture the piglets, and treatment should be initiated accordingly.
Göttingen Minipigs can be milked and used in lactation studies to evaluate the transfer of drugs from the sow to the piglets through the milk. A suitable method for milking is based on positive reinforcement training, where the desired behavior is rewarded with a treat. Training should start weeks prior to farrowing by training the sow to accept being touched and simulated milking. In addition, it is beneficial to train the sows to stand with the front legs on a step board or similar object during the milking process. The board has two main functions. It gives the sow a focus point, and it helps to overcome the anatomical challenge of the teats being close to the ground on postpartum minipigs, thus providing working space for the milking process (Ellegaard Göttingen Minipigs, Internal training protocol for milking Gottingen Minipigs).
Colostrum can be sampled immediately after farrowing without previous training of the sow as the production is high. Colostrum can be frozen without losing its immunological properties (4) and can be used when needed. Colostrum should be heated gently to 37 °C before administration and used immediately after being thawed. Although parity has no effect on the concentrations of immunoglobulins in colostrum (5), we recommend collecting colostrum from multiparous sows, since primiparous sows yield less amount (6). Furthermore, it is important to eliminate potential stress factors (such as milking) for first-time sows.
The newborn piglet
From 6 to 48 hours after birth, piglets require an iron supplement to prevent anemia (7). At this time, each piglet should be marked with their individual animal identification number to ensure proper recordkeeping. Identification can be by a chip, ear notching, or temporary marking with a dye.
Maternal antibody transfer is entirely via colostrum and not the placenta. Consumption of sufficient amounts of colostrum within the first few hours of life is thus essential for the survival and subsequent well-being of newborn piglets (8, 9). The piglets should be satisfied and alert with a rounded rather than sunken belly – in the latter case, this could indicate insufficient intake of colostrum. To increase the chance of survival for cold and weak-born piglets, colostrum can be administrated orally with a needleless syringe multiple times within the first 24 hours of life. In general, piglets should not be given more than 1 ml colostrum at a time, as larger amounts increase the risk of accidental inhalation and subsequent risk of pneumonia.
In the piglet area, the temperature must be at least 34–37°C for the first week. After that, the temperature in the area should be gradually reduced. If the piglets are cold, it may reduce their ability to absorb antibodies in the gut and they will need extra energy to raise their body temperature and maintain their metabolism. Thus, keeping the piglets warm will increase the survival rate (Picture 2).
If piglets are removed from the sow, they must be kept warm, for example by placing an electric heating blanket or a soft warming cover in the box the piglets are transported in. The time separated from the sow should be as short as possible.
Cross-fostering
Cross-fostering can be done if piglets have to be removed from an aggressive sow, to equalize litter size between sows, and for research purposes. It is crucial that all the piglets get colostrum before cross-fostering takes place, and it is recommended not to remove the piglets until their umbilical cord is dry (see Picture 3). To be certain that all piglets get a functioning teat, cross-fostering allocation must be completed preferably no more than 48 hours after farrowing. The piglets that are moved must be strong enough to handle the move, and it is advisable to remove the largest piglets from the large litter and mix them in a small warm area (34–37°C) with the piglets from the smaller litter that they are allocated to. The mixed piglets should remain together for about 30 minutes to make their scent uniform before introducing them to the sow . To stimulate milk production and facilitate the acceptance of the new piglets, the foster sow can be given ½ ml oxytocin IM in the neck muscle. It is imperative to observe the sow and her behavior for a while to make sure the piglets are accepted.
A: Newborn Göttingen Minipig with a fresh umbilical cord.
B: The umbilical cord is now dry, the belly is rounded as a sign that the piglet has received sufficient colostrum and the piglet is now ready to be placed with a foster sow.
REFERENCES
- Mikkelsen LF, Van Cruchten S, Makin A: The use of Göttingen Minipigs in juvenile studies. in Drug Discovery and Evaluation: Safety and Pharmacokinetic Assays. Edited by Hock FJ, Gralinski MR, Pugsley MK. Cham, Springer International Publishing; 2022. pp. 1-19.
- Svendsen O. The minipig in toxicology. Exp Toxicol Pathol. 2006;57:335-339.
- Ellemann-Laursen S, Marsden E, Peter B, Downes N, Coulby D, Grossi AB. The incidence of congenital malformations and variations in Göttingen minipigs. Reprod Toxicol. 2016;64:162-168.
- Ramírez-Santana C, Pérez-Cano FJ, Audí C, Castell M, Moretones MG, López-Sabater MC, Castellote C, Franch A. Effects of cooling and freezing storage on the stability of bioactive factors in human colostrum. J Dairy Sci. 2012;95:2319-2325.
- Segura M, Martínez-Miró S, López MJ, Madrid J, Hernández F. Effect of Parity on Reproductive Performance and Composition of Sow Colostrum during First 24 h Postpartum. Animals (Basel). 2020;10.
- Nuntapaitoon M, Juthamanee P, Theil PK, Tummaruk P. Impact of sow parity on yield and composition of colostrum and milk in Danish Landrace × Yorkshire crossbred sows. Preventive Veterinary Medicine. 2020;181:105085.
- National Research Council: Nutrient Requirements of Swine. 11th edition ed, The National Academies Press; 2012.
- Dividich JL, Esnault T, Lynch B, Hoo-Paris R, Castex C, Peiniau J. Effect of colostral fat level on fat deposition and plasma metabolites in the newborn pig. Journal of Animal Science. 1991.
- Quesnel H, Farmer C, Devillers N. Colostrum intake: Influence on piglet performance and factors of variation. Livestock Science. 2012;146:105-114.
