Unwavering loyalty: Piglet devotion to the chosen sow teat

Health impacts of piglets choosing a teat from their mother sow.

for decorative purposes only
Piglets suckling on mother sow. Photo by: Madonna Benjamin, Michigan State University Extension

Modern sows are highly prolific and as such the number of piglets born often outnumbers viable teats, both at an individual sow level and a farrowing room or batch level. Research proves piglet access to colostrum and milk is essential for their growth and survival. Colostrum is crucial for piglets for several reasons.

Piglets are born with limited energy reserves and deprived of antibodies and immunoglobulins. Piglets have a large surface area and very little body fat, leaving them prone to hypothermia. Ingestion of energy-dense colostrum helps piglets to maintain body temperature. It provides passive immunity to ensure their survival and development. It contains antibodies and immunoglobulins that are primarily accessed from colostrum in piglets. Furthermore, the growth factors found in colostrum assist in the closure of the gut lining, which prevents the absorption of harmful bacteria and toxins. During that suckling period, the piglet acquires essential elements to develop a good immune status, proper gut microbiota and high disease resilience for its future life.

Piglets exhibit one of the most complex nursing behaviors among mammals. The sow continuously exposes the piglets in the initial hours after birth and colostrum is always available. Newborn piglets perform the so-called ‘teat sampling behavior’ for the first 8 hours. Piglets compete over any functional teat as they move along the udder. Each piglet can suckle from seven different teats during this period, and the highest frequency of fighting occurs around 3 hours after birth.

In the next stage of nursing milk, teat sampling behavior evolves into synchronized suckling bouts over the first 12 hours. The sow initiates the nursing in early lactation. As noted by David Fraser, the sow’s milk ejection is remarkably brief, lasting only about 10-25 sec during the established lactation because the sow’s mammary gland cannot hold large volumes; the milk is available to the piglets only during milk injection. When the sow calls, the piglets are present and in position during this brief suckling event.

There are five stages or phases to piglet nursing: nursing initiation,  pre-ejection, milk ejection, postejection  and nursing termination

Most of a sow’s piglets begin to suckle and get settled permanently at their chosen nipples after 2-3 days of age. Suckling event frequency averages 25 times in 24 hours with diminished frequency throughout the lactation. Suckling synchronization and teat fidelity of littermates is achieved by day 3 or 4 post-partum.

However, sow prolificacy does not equate to more colostrum production by the sow. Subsequently, managing piglets requires strategies to equate the number of functional teats to the number of piglets, understanding how piglets select their choice of teats and understanding the exciting phenomenon of piglet teat fidelity.

Research has demonstrated that an intake of about 180 grams of colostrum per kilogram of body weight is required to provide the piglet with sufficient energy and IgG for survival. Moreover, the sow’s colostrum production was independent of her litter size and overall litter weight. There was an overall decrease of 22 grams of colostrum per additional piglet born in large litters. Therefore, in larger litters, piglets are more likely to have a reduced/inadequate colostrum intake due to competition.

If the litter is undisturbed, the piglets will have chosen their preferred teat by day 3 of nursing. Interesting, by day 10, 85% will have kept the same preferred teat pairing. This study suggests that, when possible, a high level of teat fidelity is an advantage to piglets because it reduces teat disputes and the chance of missing nursing. When we can retain good sow health, sow comfort to reduce her heat stress and ensure access to teats, then it is likely that management methods, split suckling, or cross-fostering, would affect litter teat fidelity.

However, if there are limited resources, such as less access to teats than piglets and an attempt to establish or maintain their position in the teat order, fighting would be one negative outcome of this mismatching of established and desirable teats. Fighting behavior during lactation can reduce individual piglet milk intake and increase stress, injuries and susceptibility to disease. However, if managed appropriately, the overall outcomes might improve piglet wellbeing.

While piglets have unwavering teat fidelity if undisrupted when the number of piglets outnumbers teat access, litter management strategies such as cross-fostering piglets away from their selected teats may have positive long-term impacts on survival, growth, behavior, reproductive successand immunity. For example, if cross-fostering to improve access to sow colostrum and milk is conducted post-20 hours after birth (or one day after birth), there have been no adverse effects on adopted piglet survival and growth performance. Further, cross-fostering in the first two weeks of life might increase socialization and reduce subsequent aggressive behaviors such as tail-biting in the nursery or grower stage.

Additionally, in a sow’s (gilt) first lactation, stockpersons and farmers must maximize her capacity for both current and future mammary development. Matching piglet numbers to functional teats ensures teat development for the subsequent parity. Dr. Chantal Farmer, Research Canada, notes that for those teats to have an adequate milk yield in the subsequent parity, they must be used in the first parity for at least two days of suckling.

Thus, the piglet’s loyalty to suckling their chosen teat is also responsible for establishing and maintaining milk production and is increasingly important with progressively prolific sows.