Researchers fine-tune nitrogen in pig diets

Kansas State University swine nutritionist Jason Woodworth says 70% of the costs in swine production relate to feed — a figure that can be reduced by substituting conventional crude protein sources like soybean meal with synthetic amino acids.

While that practice cheapens rations, it creates imbalances in amino acid to crude protein, which caused Woodworth and other researchers at Kansas State University to investigate how to economically formulate swine diets while keeping growth on track.

“When adding target amino acids and removing some of the crude protein that comes with the soybean meal, we can get into deficiencies of other non-essential amino acids or some of the other active components that soybean meal brings to the diets,” he said in a university news release.

In turn, Kansas State University master’s student Jessica Smallfield completed multiple feeding trials looking at the effects of standardized ileal digestible lysine to crude protein ratio on the growth performance of young pigs using different feeding strategies to answer that nutrition query.

Smallfield said, “In one instance, we composed diets to 1.15% and 1.30% SID lysine and found that pigs performed better at the higher percentage.”

Smallfield then assembled numerous diets using soybean meal and distiller’s dried grains with similar standardized ileal digestible lysine to crude protein ratios as the previous study to determine which source had the more sizable impact on growth.

“We found that pigs fed the diets with DDGs did not perform as well,” she said. “The findings from the first two studies contributed to a third trial where we added different non-protein nitrogen sources to the diets.

“Our team wanted to determine how to bring back feed efficiency and performance by supplementing nitrogen, which becomes deficient as you remove things like soybean meal and lower crude protein levels.”

Smallfield said all three trials had similar findings in determining the correct digestible lysine to crude protein ratio to feed.

“In diets with ratios above 6.5, nitrogen became the limiting growth factor,” she said. “Keeping them below 6.5 with different protein or non-protein nitrogen sources will help pigs recover lost performance.”

Beyond performance and efficiency, researchers also evaluated gut health.

“Those pigs fed the correct ratios had hindguts that were in better condition and produced less diarrhea,” Smallfield said. “Getting this ratio right can lead to better waste management, less slurry production and healthier pigs that grow more efficiently with less nitrogen excretion.”

Woodworth said, “Less nitrogen excretion is better for the environment and more sustainable at the end of the day.”