Researchers studied how a natural protein found in soybeans affects young pigs’ health and growth. They tested three different levels of this soybean protein in pig feed and exposed some pigs to a harmful bacteria. Pigs eating feed with high levels of the soybean protein grew slower and got sicker when exposed to the bacteria compared to pigs eating feed with lower levels. The findings suggest that the quality of soybean ingredients used in animal feed matters more than previously thought, especially when animals are at risk of getting sick.

The Quick Take

  • What they studied: Whether poorly processed soybean ingredients in pig feed slow growth and make pigs more vulnerable to a specific type of food-poisoning bacteria
  • Who participated: 288 newly weaned piglets (about 12 pounds each) divided into groups that either received normal conditions or were exposed to harmful bacteria
  • Key finding: Pigs eating feed with high levels of unprocessed soybean protein grew 13-16% slower, and when exposed to bacteria, they had death rates up to 23% compared to 0% in pigs eating better-quality feed
  • What it means for you: If you raise pigs or work in animal agriculture, choosing soybean feed ingredients that are properly processed may help pigs grow better and stay healthier. However, this study only looked at pigs, so results may not apply to other animals or situations.

The Research Details

Scientists divided 288 young pigs into six groups based on the quality of their soybean feed (three different quality levels) and whether they were exposed to harmful bacteria or kept healthy. Half the pigs received feed with low levels of problematic soybean protein, while others received feed with medium or high levels. On day 10, some pigs were intentionally exposed to a specific bacteria that causes diarrhea in pigs. The researchers then tracked the pigs’ growth, health, weight gain, and how many needed antibiotics or died over the next 28 days.

The study carefully controlled for pig genetics and sex to make sure these factors didn’t affect the results. Researchers also collected fecal samples regularly and examined the pigs’ intestines to understand what was happening inside their bodies when they got sick.

This research approach is important because it tests whether soybean quality matters in real-world conditions where animals might get sick. Rather than just measuring growth in healthy animals, the researchers created a realistic disease scenario to see if poor-quality feed makes illness worse. This helps farmers and feed manufacturers understand whether investing in better soybean processing is worth the cost.

This study is fairly strong because it used a large number of animals (288 pigs), carefully controlled which pigs got which feed, and measured multiple outcomes including growth, illness, and death. The researchers also examined intestinal tissue to understand the biological mechanisms. However, the study only looked at one type of bacteria and one breed of pig, so results may not apply to all situations. The study was published in a peer-reviewed journal, meaning other experts reviewed it before publication.

What the Results Show

Pigs eating feed with the highest level of problematic soybean protein (4.2 units) grew 13-16% slower than pigs eating feed with the lowest level (1.1 units), regardless of whether they were exposed to bacteria. This slower growth happened consistently across all pigs in this group.

When pigs were exposed to the harmful bacteria, the results were even more dramatic. Pigs eating medium-quality feed (2.4 units) had a 20.8% death rate when sick, compared to 0% death in healthy pigs eating the same feed. Additionally, 22.9% of sick pigs on this medium-quality feed needed antibiotics, while none of the healthy pigs on the same feed needed treatment.

Interestingly, pigs eating the highest-quality feed (1.1 units) did much better even when exposed to bacteria, suggesting that feed quality provides some protection against illness. The researchers also found that sick pigs had softer stools (lower fecal dry matter) from days 3-11 after infection, which is expected with this type of bacterial infection.

When researchers examined the pigs’ intestines under a microscope, they found that the amount of bacteria attached to the intestinal lining was similar across all feed quality groups. This was surprising because it suggested the soybean protein wasn’t directly helping the bacteria stick to the intestines. The researchers also measured fermentation byproducts in the colon and found no major differences between groups, suggesting the harmful effects weren’t simply due to changes in gut fermentation.

Previous research had shown that high levels of unprocessed soybean protein reduce how well pigs digest nutrients and can change the bacteria living in their guts. This study confirms those findings and adds new information by showing that poor-quality soybean feed makes pigs more vulnerable to specific infections. The results support the idea that feed quality matters not just for normal growth, but especially for disease resistance.

This study only tested one type of bacteria and one breed of pig, so results may not apply to other bacteria or pig breeds. The researchers didn’t measure exactly how much of the problematic soybean protein the pigs’ bodies actually absorbed, which could have provided more detail about the mechanism. Additionally, the study was conducted in controlled laboratory conditions, which may not perfectly match real farm environments where pigs face multiple stressors at once.

The Bottom Line

Feed manufacturers should prioritize proper processing of soybean ingredients to reduce levels of problematic proteins (moderate confidence). Pig farmers should consider sourcing feed from suppliers who test for soybean protein quality, especially if their pigs are at risk of infection (moderate confidence). However, more research is needed to confirm these findings apply to other situations and other types of animals.

Pig farmers, feed manufacturers, and veterinarians working with pigs should pay attention to these findings. The results are most relevant for operations raising young pigs that may be exposed to bacterial infections. Pet owners and people raising other types of animals should not assume these results apply to their situation without additional research.

Slower growth from poor-quality feed appears within the first 10 days of feeding. If pigs are exposed to infection, increased illness and death can occur within 5-12 days. Improvements in growth and health should be noticeable within 2-3 weeks of switching to better-quality feed.

Want to Apply This Research?

  • If managing a pig operation, track weekly weight gain and compare it against expected growth rates for your pig breed and age. Record any illness events, antibiotic treatments, and mortality rates weekly. Compare these metrics before and after changing feed sources to measure real-world impact.
  • Work with your feed supplier to request testing results for soybean protein quality in your feed. Request feed batches with lower levels of problematic soybean proteins (below 2.4 units if possible). Document the feed source and quality metrics for each batch used.
  • Establish a baseline of current growth rates and health outcomes over 4 weeks. After switching to higher-quality feed, continue tracking the same metrics for 8-12 weeks to see if improvements occur. Keep records of feed costs versus health improvements to determine if the investment is worthwhile for your operation.

This research was conducted on pigs and may not apply to other animals or species. The study describes laboratory conditions that may not perfectly match real-world farm environments. These findings should not replace professional veterinary advice. If you raise pigs or other livestock, consult with a veterinarian or animal nutritionist before making significant changes to feeding practices. This summary is for informational purposes only and is not a substitute for professional agricultural or medical guidance.