Calcium and phosphorus are two macro minerals that are very important to consider in all biological systems, particularly in swine production. In addition to growth and development, Jordan Gebhardt says the two minerals really “form the backbone of our bones and really dictate structural soundness and how well those animals grow and develop but also move long term.”

While ensuring an appropriate level of calcium and phosphorus is being fed to pigs to optimize bone mineralization, the Kansas State University swine nutrition veterinarian points out more is not always better.

“Phosphorus for example is one of the more expensive nutrients that we feed in swine diets so making sure that we provide sufficient phosphorus to meet our goals and our needs, but also not providing excess phosphorus, such that material then goes into the environment and has some environmental concerns, but also the economic implications of that as well,” Gebhardt says. “So really dialing in the complex relationship between calcium and phosphorus is very important in swine nutrition and swine production.”

Part of Larissa Becker’s PhD work at K-State has been diving into the literature to understand calcium and phosphorus requirements in reproducing sows, specifically for gestation and lactation.

“For gestation the sow really needs these minerals for her own skeletal development but then also to grow and develop these fetuses throughout her gestation length and so that calcium and phosphorus requirement increases throughout gestation to provide for that growing litter of pigs, and younger sows and older sows have very similar calcium and phosphorus requirements, just due to that growing litter that she is growing throughout gestation,” Becker says.

“Then in lactation these minerals are used for milk production and to feed these growing piglets, and that requirement in lactation is a little bit higher than it is during gestation just to meet the milk demands of those piglets.”

Becker’s goal for the literature review was to get a more complete picture of why the swine industry chose to feed the levels of phosphorus and calcium it does today. With only nine published studies for gestation, and seven in lactation, Becker says there is a huge need for more research specifically on calcium and phosphorus levels in gestation and lactation.

“For producers in the industry, what we're typically feeding right now is a little bit higher than what this published data says, and I think that's just because over time we've applied a margin of safety to these feeding levels, just to make sure that she's able to grow those bones but we really don't understand what she actually needs,” Becker says.

The challenge for further research in gestation and lactation on calcium and phosphorus is that in order to measure bone mineralization, bones from sows must be collected, and that can be a big limitation for this type of research, Becker says.

With the current recommended feeding levels, Gebhardt says producers won't notice any significant abnormalities as it relates to calcium and phosphorus, however if significant formulation or feed mixing errors occurs, over time health challenges can be observed on the slat level.

“We can see reductions in structural soundness or lameness, or if it gets really bad and we're feeding deficient levels for a long enough period of time, we can also see broken bones and that can be both in younger pigs, nursery pigs but also pigs going to the processing plant,” Gebhardt says. “If we see an increase in the number of broken bones, we definitely need to be thinking about our calcium and phosphorus requirements and where we have those levels set, but also is what we think we are formulating on paper is that what is actually getting in front of the animal.”

While producers may be overfeeding phosphorus to sows by a small margin, Gebhardt says there could be some opportunity for cost savings but also to more efficiently utilize that phosphorus, instead of that material then going into the manure and being applied in the fields.

“A lot of research in those areas has been conducted to establish nutrient requirements, establish the relationship between calcium and phosphorus, those two minerals are not independent of each other,” Gebhardt says. “We need to consider both of them together in those discussions, but also how certain enzymes, specifically phytase, can be used to increase the digestibility of phosphorus that's naturally found in our feed ingredients. A lot of work has been done over the last number of years related to this calcium and phosphorus area, allowing us to improve how we formulate those diets, to meet the pig's productive needs, but also do it as efficiently as possible for the producer.”

What’s next for K-State’s research in this area? Gebhardt says the first objective is to try to improve their understanding of the diagnostics associated with bone mineralization.

“From a veterinary perspective if we go in and investigate at the field level, at a producer level, lameness issues for example, or if we suspect calcium and phosphorus may be a problem in the diet, what sample do we collect? How do we collect that sample and when we work with a veterinary diagnostic laboratory what testing should we do and how do we interpret the results of those different testing parameters?” Gebhardt says.

“That's really an opportunity that we've been pretty excited about, to be able to work with nutritionists, work with veterinarians in the veterinary diagnostic laboratories, to improve our understanding of this very complex area so we hope to take the research that's being generated here at K-State and beyond, and be able to compile that and work together to best serve the needs of swine producers, both from the nutrition as well as veterinary medicine perspectives.”

Gebhart and Becker presented these findings and more during the recent K-State Swine Day. To view all of the presentations and publications, visit the K-State Swine Day website.