Soybean meal’s effect on pig growth depends on the pig’s age, according to a 2026 research analysis of six experiments involving 2,676 pigs. In very young nursery pigs (10 kg), increasing soybean meal reduced feed intake slightly. In growing pigs (43 kg), moderate soybean levels improved feed efficiency on corn-only diets. In finishing pigs (102 kg), soybean levels had no effect on growth or meat quality. Gram Research analysis shows that farmers should adjust soybean amounts based on pig age and other diet ingredients for optimal results.
Researchers conducted six large experiments to test how much soybean meal (a common protein source) should be added to pig feed at different growth stages. According to Gram Research analysis, the results showed that soybean meal affects young pigs differently than older pigs. In very young nursery pigs around 10 kg, adding more soybean actually slowed growth slightly. But in older growing pigs, moderate amounts of soybean improved how efficiently they converted feed to body weight—unless the feed also contained corn byproducts. In finishing pigs ready for market, soybean levels didn’t matter much. These findings help farmers choose the right feed recipes for each stage of pig growth.
Key Statistics
A 2026 research analysis of six experiments with 2,676 pigs found that increasing soybean meal from 25% to 36% in nursery pig diets decreased feed intake in 10 kg pigs, though growth rate remained unchanged.
In growing pigs weighing 43 kg, a 2026 study showed that increasing soybean meal in corn-only diets improved feed efficiency (the amount of feed needed to gain one pound of body weight), but this benefit disappeared when corn byproducts were included in the diet.
A 2026 analysis of finishing pigs weighing 102 kg found that soybean meal levels ranging from 10% to 23% had no effect on growth performance or meat quality characteristics, regardless of diet formulation.
Research involving 615 growing pigs showed that soybean meal increased average daily gain and feed efficiency in corn-based diets, but produced no performance differences when the diet contained 20% corn byproducts.
The Quick Take
- What they studied: How different amounts of soybean meal in pig feed affect how fast pigs grow, how well they convert feed into body weight, and the quality of their meat at different life stages.
- Who participated: Six separate experiments with a total of 2,676 pigs, ranging from very young pigs (10 kg) to nearly market-ready pigs (102 kg). Each experiment tested different soybean levels in corn-based diets, with some also including corn byproducts.
- Key finding: Soybean meal’s effect depends on pig age: it slightly reduced growth in the youngest pigs (10 kg), improved growth efficiency in medium-sized growing pigs (43 kg) when fed corn-only diets, and had no effect on the largest finishing pigs (102 kg).
- What it means for you: If you raise pigs, this research suggests you should adjust soybean levels based on your pig’s age and what other ingredients are in the feed. For very young pigs, less soybean may be better. For growing pigs on simple corn diets, moderate soybean improves efficiency. For market-ready pigs, soybean level matters less. Always consult with a nutritionist for your specific operation.
The Research Details
Researchers conducted six separate but related experiments over different pig growth stages. In each experiment, they divided pigs into groups and fed each group a different diet with varying amounts of soybean meal—ranging from as low as 9.5% to as high as 40% of the diet. Some experiments also included corn byproducts (called DDGS) to test how soybean works with other ingredients.
The experiments were carefully designed so that pigs in each group started at similar weights and were tracked for 28-30 days. Researchers measured how much the pigs ate, how much they grew, how efficiently they converted feed to body weight, and examined their manure to see how well they digested the food. For finishing pigs, they also measured the quality and composition of the meat.
This multi-experiment approach is powerful because it tests the same question across different ages and diet combinations, making the results more reliable and applicable to real farm conditions.
Testing soybean meal at multiple pig ages is important because young pigs have different digestive systems and nutritional needs than older pigs. By running six separate experiments instead of just one, researchers could see that soybean meal isn’t a one-size-fits-all ingredient. The inclusion of corn byproducts in some experiments also reflects real farming practices, where farmers often mix different ingredients to manage costs. This practical approach makes the findings directly useful to pig farmers.
This research was published in a peer-reviewed scientific journal, meaning other experts reviewed it before publication. The large sample size (2,676 pigs total across six experiments) provides strong statistical power. The experiments were randomized, meaning pigs were randomly assigned to different diet groups, which reduces bias. The researchers measured multiple outcomes (growth, feed efficiency, digestion, meat quality) rather than just one, giving a complete picture. However, the study was conducted in controlled research settings, so real-farm conditions might produce slightly different results.
What the Results Show
In the youngest nursery pigs (around 10 kg), increasing soybean meal from 25% to 36% of the diet decreased how much they ate and slightly reduced their manure quality, though it didn’t significantly slow their growth rate or feed efficiency. Interestingly, when researchers tested slightly older nursery pigs (13.5 kg), increasing soybean had no negative effects at all.
In the growing phase with medium-sized pigs (43 kg), soybean meal showed benefits—pigs grew faster and converted feed more efficiently when soybean levels increased in corn-only diets. However, when corn byproducts were included in the diet, these benefits disappeared, suggesting that soybean and corn byproducts may compete for similar digestive pathways.
In the finishing phase with the largest pigs (102 kg), soybean meal levels had essentially no effect on growth, feed efficiency, or meat quality, regardless of whether the diet contained corn byproducts or not. This suggests that by the time pigs reach market weight, their digestive systems are mature enough to handle varying soybean levels without any performance difference.
Fecal characteristics (manure quality) were affected by soybean levels in young nursery pigs, with higher soybean levels producing slightly wetter manure. This could have practical implications for barn management and pig health. In growing pigs fed corn-only diets, feed efficiency improvements with higher soybean were notable enough to potentially affect farm profitability. The lack of any carcass quality differences in finishing pigs suggests that soybean meal doesn’t negatively impact meat characteristics at any level tested.
This research builds on decades of soybean meal studies in pig nutrition by systematically testing multiple levels across all major growth stages in a single research program. Previous studies often focused on single stages or didn’t account for diet interactions with other ingredients like corn byproducts. These findings confirm that younger pigs are more sensitive to dietary changes and that ingredient interactions matter—a nuanced finding that advances practical farm nutrition.
The experiments were conducted in controlled research settings with standardized conditions, so results may differ slightly on commercial farms with variable conditions. The study didn’t test extremely high soybean levels beyond 40%, so we don’t know if even higher levels would show different effects. Individual pig genetics and health status weren’t analyzed, so some variation between individual pigs wasn’t explained. The study focused only on corn-based diets with or without corn byproducts, so results may not apply to diets based on other grains or ingredients.
The Bottom Line
For nursery pigs around 10 kg, keep soybean meal at 25-29% to avoid reducing feed intake (moderate confidence). For growing pigs (40-45 kg) on corn-only diets, soybean meal at 26-30% can improve feed efficiency (moderate-to-high confidence). For finishing pigs (100+ kg), soybean levels between 10-23% have no practical difference on growth or meat quality (high confidence). If your diet includes corn byproducts, reduce expectations for soybean benefits in the growing phase (moderate confidence). Always work with a nutritionist to balance soybean with other ingredients and your farm’s specific goals.
Commercial pig farmers and nutritionists should use these findings when formulating diets for different pig ages. Feed manufacturers can use this data to create age-appropriate feed products. Researchers studying swine nutrition will find this useful for understanding how ingredients interact. Consumers interested in how pigs are raised may appreciate knowing that feed formulation is carefully optimized. People not involved in pig farming or nutrition don’t need to apply these findings.
Changes in pig growth performance from diet adjustments typically appear within 1-2 weeks of feeding the new diet, as seen in these 28-30 day experiments. Feed efficiency improvements in growing pigs would be measurable within 3-4 weeks. Finishing pigs would show any changes (or lack thereof) within their typical 4-6 week finishing period. Manure quality changes in young pigs can appear within days of diet changes.
Frequently Asked Questions
Does soybean meal help pigs grow faster?
It depends on the pig’s age. In growing pigs (40-45 kg), moderate soybean levels improve how efficiently they convert feed to body weight on corn-only diets. In very young and finishing pigs, soybean levels don’t significantly affect growth speed.
How much soybean should I put in pig feed?
For 10 kg nursery pigs, use 25-29% soybean meal. For 43 kg growing pigs on corn diets, use 26-30%. For finishing pigs over 100 kg, use 10-23% with no expected performance difference. Always consult a nutritionist for your specific operation.
Does soybean meal affect meat quality in pigs?
No. A 2026 study of finishing pigs found that soybean meal levels had no effect on meat quality or carcass characteristics, meaning farmers can adjust soybean amounts without worrying about meat composition changes.
What happens if I mix soybean with corn byproducts in pig feed?
When corn byproducts (DDGS) are included in the diet, the growth benefits of soybean meal in growing pigs disappear. The two ingredients appear to compete, so you shouldn’t expect efficiency improvements from adding soybean if byproducts are already in the feed.
Can young piglets handle high soybean diets?
Young nursery pigs around 10 kg show reduced feed intake with very high soybean levels (36%), though growth rate isn’t severely affected. Slightly older nursery pigs (13.5 kg) tolerate high soybean without problems, suggesting digestive maturity matters.
Want to Apply This Research?
- If managing a pig operation, track weekly feed intake and weight gain by diet group, calculating feed conversion ratio (pounds of feed per pound of gain). Compare these metrics against the baseline for your pig age group to see if your soybean level is optimized.
- Adjust soybean meal percentages in your feed formulation based on pig age: reduce to 25-28% for 10 kg nursery pigs, increase to 26-30% for 43 kg growing pigs on corn diets, and use 10-23% for finishing pigs without expecting major differences. Document these changes and monitor results.
- Maintain a feeding log that records soybean meal percentage, pig age/weight, daily feed intake, weekly weight gain, and feed conversion ratio. Review monthly to identify trends and compare against these research benchmarks. Adjust formulations if your results deviate significantly from expected performance.
This research applies specifically to commercial pig production and feed formulation. Results were obtained in controlled research settings and may vary under different farm conditions, management practices, and pig genetics. Farmers should consult with a swine nutritionist or veterinarian before making significant changes to pig feed formulations, as individual farm conditions, pig health status, and economic factors should be considered. This information is for educational purposes and does not replace professional agricultural or veterinary advice. Always follow local regulations regarding animal feed and care.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.