During assistant professor Crystal Levesque's doctoral research at the University of Alberta, the pig nutritionist found that a sow's protein requirement in late pregnancy was substantially higher than in early pregnancy.

The bulk of piglet growth takes place in the final trimester, she explained.

In 2012, the US National Research Council developed nutritional models for gestating and lactating sows, but Ms Levesque said: "those models are based on very little data."

Phase feeding is used to meet the changing nutritional requirements of nursery and growing pigs, but gestation barns are not designed for feeding multiple diets, according to Ms Levesque.

Consequently, the solution thus far has been simply to increase or bump up the sow's feed ration.

However, she pointed out, the question remains whether phase feeding a diet formulated especially to meet a sow's changing gestational needs would produce a better outcome.

"The hierarchy of nutrient demand shifts during late gestation," she said. "The developing fetuses become the primary target for dietary nutrients and the sow takes what's left over."

Once the piglets are born, milk production in the first week or so generally requires more feed than the sow can consume. That means that a sow that goes into lactation at a low body condition will become even more nutritionally deficient.

A young sow also needs to be able to develop her own body as well as support growing fetuses and then nursing piglets, she added.

In a 30-sow pilot study comparing bump feeding and stage feeding, Ms Levesque has found "fairly clear preliminary evidence that we're impacting at least piglet survivability in the first week post-weaning."

According to 2014 National Pork Board statistics, the average pre-weaning mortality rate is 17.3 per cent, Ms Levesque noted. If bump feeding results in saving even one piglet per sow each year, the producer stands to gain $200 per animal, depending on the market price, without changing herd size or genetics.

However, Ms Levesque admitted: "The cost of changing the barn to allow us to phase feed is phenomenal."

The economic benefit must justify the cost of retrofitting the barn and changing the way things are done.

To determine whether phase feeding is cost-effective, research trials using at least 100 animals of equal age per treatment are necessary. Following the successful pilot study, the researchers hope to repeat the study and complete a full-scale economic analysis in a new swine research facility planned in South Dakota.

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