“The first three days are critical”: Danish research aims to improve survival of low birth weight piglets

The increasing size of litters has brought with it a mounting industry challenge: low birth weight piglets. While genetic advancements have boosted productivity, they have also resulted in more small, vulnerable piglets at birth. These piglets often struggle to compete for colostrum, are more prone to hypothermia and face a significantly higher risk of death.  

Dr. Madsen is working to understand why these piglets fail to thrive, or even catch up with their pen mates, and how to change that trajectory. 

“From my point of view, the biggest challenge low birth weight pigs pose is that they increase the mortality rate in the litter,” said Dr. Madsen. “They simply die because they have low energy reserves, hypothermia and/or undernutrition.” 

The long-term effects are just as concerning. According to Madsen, low birth weight piglets that survive often lag behind their litter mates throughout their lifespan. They grow more slowly, have poorer feed efficiency and typically reach market weight later. Even at slaughter, their carcasses may yield less desirable traits, ultimately diminishing economic returns. 

“They probably have lower quality carcass traits,” Madsen explained. “So overall, they are impairing the economy and the sustainability of the pig production.” 

How low is “low”? 

There’s no universal definition of a low birth weight piglet. In Denmark, where larger litters are the norm, Dr. Madsen tends to view piglets under 800 grams as particularly at risk. However, he noted that some industry professionals set the cut-off as high as 1.2 kilograms. 

“It really depends on the genetics that you use and the litter size,” he said. “But I would say below 800 grams, they start to get complicated. They are tough.” 

The lasting impact of IUGR 

A major contributing factor to low birth weight is intrauterine growth restriction (IUGR), a condition in which the fetus fails to develop properly during gestation. Not all low birth weight piglets suffer from IUGR – some may simply be small but otherwise healthy. However, identifying the difference is not easy. 

“There is a fairly great proportion that have been exposed to IUGR, and they will be negatively impacted the rest of their life,” said Madsen. “It’s very difficult to reverse the negative impact.” 

The implications for producers are serious: many of these piglets consume resources while delivering reduced performance throughout their lifespan. Finding effective interventions is important not just for animal welfare but for the economic sustainability of the industry.

An artificial sow udder mimics nursing 

To help piglets better engage with artificial nutrition, Madsen’s collaborators developed an innovative tool: a simulated sow udder. Created by Danish agricultural research group SEGES, this “artificial udder” included soft teats to mimic the natural nursing experience. 

“There have been some older studies that suggested that piglets are more likely to drink if it’s an artificial udder rather than a cup,” Madsen noted. “But they can learn to drink from the cup very early, that’s for sure.” 

More research is needed to determine which feeding methods are most effective, and how to encourage consumption among the smallest and weakest animals. Madsen pointed out that behavioral stress, environmental conditions, and even social cues from litter mates may play a role. 

“We don’t know enough about how we can get them to eat,” he admitted. “And we don’t know enough about how they respond to the artificial rearing?” 

Practical on-farm strategies 

Many farms in Denmark already use nurse sows to support the care of low birth weight piglets. While effective in redistributing feeding pressure, nurse sow systems require careful management and come with trade-offs. 

“If you use the nurse sows, you have to move the piglets around a lot and you don’t know the age of the piglets,” Madsen said. “And that may cause a problem when you wean the piglets, because the development of the digestive system depends on age and not size.” 

Moreover, high piglet movement can increase the risk of disease transmission and labor costs. As a result, some researchers advocate combining nurse sow use with other strategies like temporary artificial rearing or supplemental nutrition. 

“You could maybe combine different strategies – maybe use nurse sows only for the small piglets, for example, for the IUGR, in combination with some temporary artificial rearing and some optimized milk replacer,” he suggested. 

However, the economics of such systems remain a concern for producers.  

“They will not buy a very expensive milk replacer if they don’t get anything out of it,” Madsen noted. 

Can sow nutrition help? 

Madsen has explored how sow nutrition during gestation can influence piglet birth weight and survivability. His work includes studying the effects of l-arginine supplementation. 

“It has some effect enlarging the myofibers or the muscle cells, which offers the potential for better muscle development in utero that could enhance postnatal growth performance,” he said.  

There is also growing interest in strategies to reduce the duration of farrowing. If piglets are born faster and more efficiently, they may have a better shot at getting colostrum before becoming hypothermic or energy deficient. 

“If you get piglets out faster, there is a longer time for all the pigs to get sufficient amounts of colostrum,” Madsen noted. 

Researchers have also considered glucose supplementation for sows before farrowing and the use of colostrum alternatives.