Sow Udder Health: How Morphology Impacts Piglet Survival
"Uncover the critical link between a sow's udder traits and piglet well-being, with key insights for modern swine farming."
In modern swine farming, rapid genetic selection has increased efficiency in feed conversion, growth rate, and carcass leanness. However, these improvements have often come at the cost of piglet mortality around farrowing. Sow maternal ability is crucial for improving overall production and welfare, which is often similar across livestock sectors.
While udder characteristics in dairy cattle have been extensively studied, pig udder morphology has received less attention, despite its fundamental role in nursing piglets. Swine breeding programs typically focus on teat number and functionality, but a comprehensive genetic evaluation of udder morphology and its relationship to production traits has been lacking.
This article explores the heritability of udder morphology traits and colostrum quality in sows, along with their genetic and phenotypic correlations with other production and reproduction criteria. The aim is to provide insights into how udder traits influence piglet survival and inform breeding strategies to enhance maternal performance.
Why Udder Morphology Matters
Sow udder morphology can influence how effectively piglets locate and use functional teats during the vulnerable period from birth to weaning. Differences in udder structure may therefore affect access to nursing, growth, and survival, although the specific scale of these effects depends on the sow, litter, and farm environment. A cautious assessment should treat morphology as one factor within a broader maternal and neonatal system.
Measuring Udder and Survival Traits
Research has developed a methodology for measuring sow udder conformation so that udder traits can be studied in relation to piglet survival, health, and performance. Other studies evaluate survival using multiple characteristics, including parity, litter weight, mean piglet birth weight, sow backfat, gestation length, farrowing duration, litter size, birth order, and farrowing assistance. A 2025 study also investigated simulated udders as an alternative to sow nursing, with the aim of addressing starvation, chilling, and death while potentially reducing reliance on nurse sows.
An Evolving Field
The study of sow udder health has gradually moved from broad observations of maternal performance toward more structured evaluation of udder conformation and piglet outcomes. Foundational work in this area established the importance of describing measurable udder traits rather than treating the udder as a uniform structure. This progression has helped frame piglet survival as a result of interacting sow, piglet, and environmental factors.
What Udder Traits Really Matter?
The study, conducted on 988 Meidam sows, recorded several udder morphology traits, including teat length, teat diameter (DIA), interteat distance within the same row (SAMER), and teat distance from the abdominal midline (AML). Researchers also assessed udder development score (DEV), the proportion of teats oriented perpendicular to the udder, and the proportion of nonfunctional teats. Colostrum IgG concentration was estimated using a Brix refractometer.
- Teat length: h² = 0.46
- Teat diameter (DIA): h² = 0.56
- Interteat distance (SAMER): h² = 0.37
- Teat distance from the abdominal midline (AML): h² = 0.22
- Udder development score (DEV): h² = 0.25
- Proportion of nonfunctional teats: h² = 0.30
- Proportion of teats oriented perpendicular to the udder: h² = 0.10
- Colostrum IgG concentration: h² = 0.35
Current Research Directions
Recent work is examining both the physical characteristics of the sow udder and possible alternatives to conventional nursing. Research on simulated udders addresses survival and weight gain in neonatal piglets, while narrative reviews consider the combined effects of sow characteristics, piglet characteristics, and the environment on pre-weaning survival. Together, these directions suggest that current research is combining morphology, management, and broader survival biology.
Limits of Simulated Nursing
A practical farm study found that using a simulated udder did not produce significant changes in piglet survival, although it affected weight gain compared with sow nursing. The authors cautioned that the sample size was too small to detect smaller effects, while reporting no negative consequences from simulated udders. This result limits claims that simulated udders reliably improve survival, even though they may remain a potentially safe management tool.
Simulated Udders and Piglet Safety
The simulated udder was designed to use attractive stimuli in the farrowing crate to draw piglets away from the sow and into a safer area. This approach specifically targeted crushing by the sow, which the research describes as a major financial loss for the swine industry. However, a later practical-farm study reported no significant improvement in survival, though it did observe an effect on weight gain and noted that the sample size limited detection of smaller effects.
Why Sow Udder Health Should Be a Priority
This study underscores the importance of udder morphology traits for piglet survival and overall farm productivity. By including udder quality traits in breeding goals and appropriately weighting them with other important traits, breeders can enhance maternal performance and reduce piglet mortality. Further research is needed to develop comprehensive udder evaluation scores and explore the relationships between udder traits and piglet outcomes in different farming systems.
Survival Is Multifactorial
Pre-weaning piglet mortality remains a serious challenge because it affects animal health, welfare, performance, and overall farm success. The cited narrative review emphasizes that survival reflects a complex relationship among sow traits, piglet traits, and environmental factors. Udder morphology should therefore be interpreted as part of an interconnected system rather than as an isolated explanation for survival outcomes.
Breeding for Longevity
Recent analysis of sows born from 2000 to 2024 found that total number born increased steadily by 0.16 piglets per litter each year. The study used continuous-time survival analysis, stratified by sow birthyear and adjusted for a random farm effect, while modeling average lifetime total number born per sow as a curvilinear covariate. These findings point toward future breeding and management work that must consider both increasing litter size and the long-term survival of sows.
The Hyperprolific Sow Challenge
The rapid adoption of hyperprolific sow genetics has created new possibilities while intensifying challenges for neonatal health, welfare, and survival. Larger litters increase variation in birth weight, intensify competition for colostrum, and heighten vulnerability to early-life disorders. Udder function and morphology must therefore be considered within the wider pressures created by modern litter sizes.
Nutrition Around Parturition
Sow nutrition around parturition has been examined in relation to fetal glycogen deposition and the production and composition of colostrum and transient milk. These maternal nutritional processes are directly relevant to the conditions neonatal piglets experience immediately after birth. The research highlights how practical decisions around the sow can influence the biological resources available during early survival.