By Madonna Benjamin, DVM, Michigan State University

Modern sows are highly prolific ¹, and as such, the number of piglets born often outnumbers viable teats, both at an individual sow level and a farrowing room/batch level.

Research is conclusive that piglets' access to both colostrum and milk are essential for their growth and survival ^2,3. 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 ⁴. In the initial hours after birth, the sow continuously exposes the piglets and colostrum in always available. Newborn piglets perform the so-called ‘teat sampling behavior’: for the first eight hours. At this time, piglets compete over any functional teat as they move along the udder⁵. Each piglet can suckle from seven different teats during this period, and the highest frequency of fighting occurs around three 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 seconds during the established lactation because the sow's mammary gland lacks the capacity to hold large volumes; the milk is available to the piglets only during milk injection ⁶.  When the sow calls, the piglets are present and in position during this brief suckling event⁷.

There are five stages or phases⁸ to piglet nursing:

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 is on average of 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 ⁴.

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 and understand how piglets select their choice of teats and the exciting phenomenon of piglet teat fidelity.  

Research by Quesnel ⁵ and others has demonstrated that an intake of about 180 g colostrum/ kg 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. In large litters, there was an overall decrease of 22 g of colostrum per additional piglet born⁹. Therefore, in larger litters, piglets are more likely to have a reduced/inadequate colostrum intake due to competition.

According to de Passille ¹⁰, if the litter is undisturbed, the piglets will have chosen their preferred teat by day 3 of nursing. Interestingly, 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. Certainly, when we can retain good sow health, sow comfort to reducer her heat stress, and ensure access to teats, then it is likely that management methods, split suckling or cross-fostering, would affect litter teat fidelity².  

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 lead to reduced individual piglet milk intake and increase stress, injuries, and susceptibility to disease.  However, if managed appropriately, the overall outcomes might improve piglet well-being.

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 success, and 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 the survival and growth performance of adopted piglets ¹¹. 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 stage¹².

Additionally, it is important in a sow’s (gilt) first lactation that stockpersons and farmers maximize her capacity for both current and future mammary development. Matching piglet numbers to functional teats ensures teat development for the subsequent parity. Chantal Farmer, Research Canada, notes that for/those teats to have an adequate milk yield in the next parity, it needs to be used in the first parity for at least two days of suckling.¹³

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.  

References