Rethinking U.S. Soybean Meal: functional compounds are reshaping swine nutrition

28 January 2026

7 minute read

By: Sarah Mikesell

North America

New research is reshaping how nutritionists think about soybean meal. Traditionally recognized as a highly digestible source of amino acids and protein, soybean meal derived from U.S. Soy is gaining fresh attention for its functional bioactive compounds, which influence immune response, gut integrity and resilience during outbreaks of respiratory disease and amid heat stress also known as the “summer dip”.

Dr. Tom D’Alfonso, Worldwide Director of Animal Nutrition at the U.S. Soybean Export Council (USSEC), said research is moving quickly and revealing layers of value that extend far beyond outdated crude protein measurements. 

Roughly 40% of soybean meal derived from U.S. Soy consists of bioactive compounds such as isoflavones, saponins, bioactive peptides and functional fibers. He said he industry is in the process of learning how these components support the immune system and increase digestive efficiency during disease and heat stress.

These compounds, D’Alfonso explained, are dramatically changing how researchers approach swine nutrition strategy. 

“The reason these compounds are interesting is because they all play a role in how an animal’s immune system responds to stress, pathogens and even dietary changes,” he said. 

Bioactive compounds support immune defense, reduce inflammation

While inflammation is a normal first response to pathogens and stress, prolonged inflammation diverts energy away from growth. D’Alfonso emphasized that this interaction between nutrition and immunity is central to understanding performance losses in challenged herds. Multiple functional compounds in soybean meal influence immune signaling, macrophage activity and metabolic energy use.

“In animals, health, nutrition, immune system and various other systems are working in dynamic processes together,” he said. “Inflammation is good. It’s often called a double-edged sword because it’s a defense mechanism. It clears out some pathogens, but too much inflammation starts to be a drain on the immune system.”

Compounds such as isoflavones and saponins appear to help regulate that response and allow pigs to allocate more metabolic energy toward growth rather than immune defense alone. 

“By having higher levels of macrophage activity, you get a faster, more efficient response,” he said.

Those effects become critically important when barns experience disease cycles or climatic heat variables that suppress feed intake and slow growth trajectories.

Respiratory disease: Protecting intake and feed conversion

Respiratory pathogens remain one of the most economically damaging challenges in finishing barns. When pigs become sick, they behave much like people do: they lose their appetite, rest more and consume less feed. That decline cascades into lower growth rates, wider herd variation and increased mortality risk.

“If you have a respiratory challenge, you just don’t feel like eating as much,” D’Alfonso explained. “A respiratory challenge creates lethargy; pig become less active and consumption goes down.” 

He noted that performance indicators worsen rapidly with the severity of infection.

“The most noticeable impact is a decrease in consumption, resulting in a decrease in feed efficiency. Unfortunately, it could be mean increases in mortality,” he said. 

Research findings underscore the potential economic impact. Feeding higher soybean meal inclusion levels of 20% to 30% during respiratory disease periods “alleviated many of these symptoms and in some cases reduced mortality by 50%,” he said, noting significant economic advantages when diets maintain high-quality soybean meal derived from U.S. Soy.

The benefits are not only health-based; they are directly quantifiable in feed savings. Pigs facing respiratory challenges but fed higher soybean meal levels required dramatically less feed to reach market weight. 

“The research shows that keeping inclusion levels of high-quality soybean meal in the diet at around 25% alleviated many of these symptoms,” he said. “The animal will need to consume more if it is digesting less,” he explained. 

Better digestibility means more efficient nutrient uptake and reduced metabolic waste.

The summer dip: How to recover performance during heat stress

Heat stress is another recurring obstacle producers prepare for each year. Known among US swine producers as the “summer dip,” higher temperatures trigger sharp declines in feed intake and growth rate and reduce uniformity across the finishing period.

Heat stress disrupts barn management and timelines by slowing the rate at which market weights are achieved. 

“Increasing the soybean meal level in hot weather diets recovers a lot of the performance that was lost,” D’Alfonso said. 

He cautioned that previous disease challenges amplify the problem, in particular, if there were respiratory challenges prior to the heat stress.

The variation in performance becomes an economic burden by forcing multiple marketing shipment groups, slowing throughput and reducing the percentage of pigs sold in processor target windows. 

“With heat stress, you get less uniformity,” he said. “It’s harder to manage the feeding schedule because you’re counting on some assumptions that you have the animals at a certain body weight at a certain time.”

D’Alfonso shared published findings showing the potential range of loss and revenue tied to soybean meal inclusion.

“Heat stress can impact consistency and cost about $1-$2 per pig, but in the case of a disease challenge or severe heat stress, it could cost $10 a pig on a traditional diet,” he said. “

Even seemingly modest dollar amounts scale quickly when barns turn over tens of thousands of animals.

“However, studies showed that having higher levels of soybean meal made from US soy in the diet was worth a $14 increase in revenue,” he said.

How isoflavones, saponins and bioactive peptides work

Among the functional compounds currently receiving the most attention, isoflavones stand out for their immune-modulating properties. D’Alfonso called them “some of the most exciting functional compounds that we’re seeing,” describing multiple modes of action. 

“Isoflavones are anti-inflammatory. They regulate immune modulation with macrophages that can surround pathogens and attack them.”

He added that performance benefits have also been observed in response to vaccination, noting “vaccines are more effective in the presence of isoflavones.”

Saponins act locally to protect the gut and strengthen the epithelial barrier in the gut, so pigs don’t get secondary infections amid disease challenges. Saponins also have a role in mucin production which is essential for protecting the respiratory tract. 

“Saponins are antimicrobial and they disrupt microbial membranes,” he said. “They basically break the cell walls and decrease pathogen load in the intestine.” 

Bioactive peptides, while newer to many nutritionists, are similarly promising. D’Alfonso explained: “The way to think about peptides is to think of them as a precursor to amino acids – a precursor to what’s collectively called protein.” 

Peptides also play roles in immunoglobulin production and antimicrobial activity, he said.

Gut integrity as the foundation of performance

Across all stress types, gut health repeatedly emerged as the essential platform for successful growth. 

“It’s good to think about digestion as being high quality ingredients that are highly digestible,” D’Alfonso said. “A high performing digestive system should function with good mucin production, healthy villi and a good balance of healthy bacteria versus pathogenic.”

When immune and digestive systems can operate efficiently, he said, reaching an animal’s genetic and production potential becomes a management outcome. 

Return to revenue, not just least-cost diet

While nutritionists often focus on cost per ton or feed conversion, D’Alfonso emphasized that economics must prioritize revenue gains from faster throughput, better uniformity and tighter processor grid targeting. 

“Revenue is often forgotten when making management decisions in animal production,” he said.

Uniformity directly affects processor payment schedules, particularly for branded programs. 

“We see this with companies like Hormel, who has the famous ‘red zone’,” he said, referring to carcass composition targets. Falling outside target thresholds reduces pay per pound.

Better performance through functional compounds positions producers to avoid multi-group marketing, minimize stress events and optimize processing windows.

Why use U.S. Soy? 

The conversation concluded with a broader overview of why origin matters. Soybean uniformity begins before the feed mill, with consistent agricultural practices and drying methods. 

“It is the sustainable farming practices of the U.S. Soy farmer that leads to a lot of this value in consistency and the composition of soybean meal,” D’Alfonso said. 

He noted multi-generation farming practices and expertise, early adoption of precision tools and natural field drying practices that protect amino acids and functional components from heat damage.

US Soybeans dry naturally in the field, while soy from tropical climates like Brazil typically undergoes mechanical furnace drying. 

“Those wet conditions in Brazil and Argentina require the soybeans to be mechanically dried typically with furnaces that are burning eucalyptus logs,” he said. “The functional compounds are affected by heat damage, so you can’t think of soybeans just as a commodity to buy because not all beans are created equally.”

For that reason, he recommended nutritionists establish minimum soybean meal inclusion thresholds across formulations, using soybean meal derived from U.S. Soy.

It’s time to rethink soybean meal

While the industry has long acknowledged soybean meal as a core protein source, research into functional compounds is demonstrating their importance as a bioactive ingredient that protects performance when it matters most. 

As D’Alfonso summarized, when performance, consistency and economics intersect, putting soybean meal at the foundation of swine diets is a strategic choice. 

“Healthy animals in a well-managed environment with low pathogens just need the right diet to reach their genetic potential. And that right diet should have a good amount of U.S. Soybean meal in it,” he concluded.