Research shows that reducing dietary protein in newly weaned piglets from 24% to 17% significantly decreases post-weaning diarrhea rates while maintaining reasonable growth, though high-protein diets do produce faster weight gain. A 2026 study of 792 piglets found that high-protein feeding increased diarrhea incidence and nitrogen waste excretion, while lower-protein diets improved digestive health. According to Gram Research analysis, farmers must balance maximum growth speed against better digestive health when choosing protein levels for young pigs.
A new study tested different protein levels in feed for newly weaned piglets to see how it affected their health and growth. Researchers found that while high-protein diets helped piglets grow faster and gain weight more efficiently, these piglets also got diarrhea more often and produced more waste nitrogen. Lower-protein diets reduced diarrhea problems, even though the piglets didn’t grow quite as fast. Adding a special enzyme to the feed showed mixed results depending on the protein level. According to Gram Research analysis, this research suggests farmers face a trade-off between maximum growth and better digestive health in young pigs.
Key Statistics
A 2026 study of 792 newly weaned piglets found that those fed high-protein diets (24% crude protein) showed the highest growth rates and feed efficiency, but experienced significantly greater post-weaning diarrhea incidence compared to piglets fed lower-protein diets (17% crude protein).
In a research article examining 792 piglets across three protein diet levels, high-protein feeding resulted in substantially higher nitrogen excretion in waste, meaning more expensive protein was lost rather than retained in the piglets’ bodies for growth.
A 2026 factorial study of 792 piglets found that adding xylanase enzyme to feed showed inconsistent results: it tended to reduce diarrhea in high-protein diet groups but increased diarrhea problems in lower-protein diet groups.
Research on 792 newly weaned piglets revealed that lower-protein diets (17% crude protein) achieved better nitrogen retention efficiency and lower diarrhea rates compared to high-protein diets, though with slightly reduced growth performance.
The Quick Take
- What they studied: Whether reducing protein in piglet feed could prevent diarrhea while still keeping them healthy and growing well, and whether adding a special enzyme could help with either diet.
- Who participated: 792 newly weaned piglets between 17 and 22 days old, weighing about 6.2 kilograms on average. The pigs were divided into groups eating different protein levels for about 5 weeks.
- Key finding: Piglets eating high-protein feed grew faster and converted feed to body weight more efficiently, but they got diarrhea more often. Piglets on lower-protein feed had fewer diarrhea problems but didn’t grow quite as quickly.
- What it means for you: If you raise pigs, you may need to choose between maximum growth speed and better digestive health. Lower-protein diets appear safer for preventing diarrhea in young pigs, though growth rates are slightly reduced. Talk to a veterinarian about what’s best for your specific situation.
The Research Details
Researchers divided 792 newly weaned piglets into six different groups based on two main factors: protein level in the feed and whether a special enzyme was added. Three protein levels were tested: low protein with standard amino acids, low protein with extra amino acids, and high protein with extra amino acids. Half of each group received feed with an added enzyme called xylanase, while the other half received regular feed. The piglets were fed in three different phases over about 5 weeks, with the protein and amino acid levels adjusted for each phase as the piglets grew.
To understand what was happening inside the piglets’ bodies, researchers moved some piglets to special cages where they could measure exactly how much food went in and how much waste came out. They collected all the feces and urine for 4 days to calculate how much nitrogen the piglets were keeping in their bodies versus losing. They also looked at what was happening in the piglets’ intestines by examining tissue samples and the contents of their digestive tracts.
This approach allowed researchers to see not just how fast the piglets grew, but also what was happening with their digestion, their health (specifically diarrhea rates), and how efficiently their bodies were using the protein in their feed.
Understanding how protein affects young piglets is important because high-protein feed is expensive and also creates environmental problems through excess nitrogen in animal waste. If lower-protein diets can prevent diarrhea without hurting growth too much, farmers could save money and reduce pollution. This study looked at the actual biological reasons why protein might cause diarrhea, examining the specific compounds produced during digestion that might be harmful.
This study was well-designed with a large number of piglets (792 total) divided into many treatment groups, which makes the results more reliable. The researchers used a factorial design, meaning they tested two factors (protein level and enzyme addition) at the same time, which is efficient. They didn’t just measure growth; they also directly measured what was happening in the piglets’ bodies through metabolism studies and tissue examination. However, the study was conducted in a controlled research setting, so results might differ slightly on actual farms with different conditions.
What the Results Show
Piglets fed the high-protein diet (24% crude protein) showed the best growth performance overall, with the highest average daily weight gain and the most efficient feed conversion. This means they gained more weight per pound of feed eaten compared to the lower-protein groups. However, these same high-protein piglets experienced significantly higher rates of post-weaning diarrhea compared to both lower-protein groups.
When researchers looked at nitrogen retention—how much of the protein the piglets’ bodies actually kept versus how much was lost in waste—the high-protein diet resulted in much higher nitrogen excretion. This means more of the expensive protein was being wasted rather than building the piglets’ bodies. The lower-protein diets, particularly the one with 17% crude protein, showed better nitrogen retention efficiency and lower diarrhea rates.
The special enzyme (xylanase) that was added to some feeds showed inconsistent results. In piglets eating the high-protein diet, the enzyme tended to slightly reduce diarrhea, but in piglets eating the lower-protein diets, the enzyme actually appeared to increase diarrhea problems. This suggests the enzyme works differently depending on the protein level in the feed.
When researchers examined specific compounds produced during digestion—particularly cadaverine and putrescine, which are potentially harmful byproducts of protein breakdown—they found these were not significantly different between protein levels. However, the enzyme tended to reduce cadaverine production across all diet types, though this difference was not quite statistically significant.
The study found that the relationship between protein level and diarrhea was consistent across the different feeding phases, suggesting this pattern holds true as piglets grow from very young to older nursery age. The enzyme addition had different effects depending on the protein level, indicating that feed additives don’t work the same way in all situations. Intestinal tissue samples showed differences between groups, though the specific details of these differences weren’t fully explained in the abstract, suggesting there were measurable changes in gut health related to diet composition.
This research confirms what previous studies have suggested: that high-protein diets can increase diarrhea problems in newly weaned piglets. The study adds new information by directly comparing different protein levels and testing an enzyme additive at the same time. The finding that lower-protein diets reduce diarrhea while maintaining reasonable growth aligns with the theory that undigested protein in the hindgut produces harmful fermentation byproducts. However, the mixed results with the enzyme suggest that previous research on enzyme additives may have oversimplified how they work.
This study was conducted in a controlled research facility with carefully managed conditions, so results might differ on commercial farms where conditions are less controlled. The study focused on newly weaned piglets and may not apply to older pigs. The researchers measured some compounds (like cadaverine and putrescine) that might explain diarrhea, but the differences weren’t always statistically significant, suggesting other factors might also be involved. The enzyme used (xylanase) is just one type of enzyme additive, so results might differ with other enzyme products. Finally, while the study measured many important outcomes, it didn’t track long-term health effects beyond the 5-week study period.
The Bottom Line
For pig farmers: Consider using lower-protein diets (around 17% crude protein) for newly weaned piglets if diarrhea is a problem, as this appears to reduce disease without severely limiting growth. The enzyme additive showed mixed results and may not be necessary or helpful for all diet types—consult with a nutritionist before adding it. Monitor your specific piglets’ growth and health to find the best balance for your operation. Confidence level: Moderate to high for diarrhea reduction; moderate for growth trade-offs.
Pig farmers and producers, especially those dealing with post-weaning diarrhea problems, should pay attention to this research. Veterinarians advising on piglet nutrition would find this useful. Feed manufacturers developing products for young pigs should consider these findings. This research is less relevant for people raising other types of animals or for those not involved in commercial pig production.
Changes in diarrhea rates should be observable within the first 1-2 weeks after switching to a lower-protein diet. Growth rate differences would become apparent over 3-4 weeks. The full benefits of reduced nitrogen excretion (better environmental impact and feed efficiency) would be seen across the entire 5-week nursery period.
Frequently Asked Questions
Does high protein cause diarrhea in young pigs?
High-protein diets significantly increase diarrhea in newly weaned piglets. A 2026 study of 792 piglets found that those fed 24% protein had much higher diarrhea rates than piglets fed 17% protein, though the high-protein group grew faster overall.
What protein level is best for preventing diarrhea in weaned piglets?
Research suggests 17% crude protein diets reduce post-weaning diarrhea while maintaining acceptable growth rates. A study of 792 piglets showed this level significantly decreased diarrhea compared to 24% protein, though growth was slightly slower than the highest-protein option.
Can enzymes help prevent diarrhea in piglet feed?
Enzyme effectiveness depends on protein level. A 2026 study found xylanase enzyme tended to reduce diarrhea in high-protein diets but increased it in lower-protein diets, suggesting enzymes don’t work the same way in all feed formulations.
How much nitrogen waste can lower-protein diets reduce?
Lower-protein diets (17% vs. 24%) showed substantially better nitrogen retention efficiency in a 792-piglet study, meaning significantly less expensive protein was wasted in manure, reducing both costs and environmental impact.
Will piglets grow slower on lower-protein diets?
Yes, but the difference is modest. A 2026 study of 792 piglets found that 17% protein diets produced slightly lower growth rates than 24% protein, but still achieved reasonable performance while dramatically reducing diarrhea problems.
Want to Apply This Research?
- Track daily diarrhea incidence rate (percentage of piglets with diarrhea each day) and average daily weight gain by diet type. Record these metrics weekly to see trends over the 5-week nursery period.
- If using the app to manage a pig operation, switch feed formulations from high-protein to lower-protein options (around 17% crude protein) for newly weaned piglets, and monitor the resulting changes in health and growth metrics within the app.
- Set up automated alerts in the app when diarrhea incidence exceeds 15% in any group, and track feed conversion ratio (pounds of feed per pound of gain) weekly. Compare these metrics between diet types to identify which approach works best for your specific operation.
This research applies specifically to newly weaned piglets in controlled research settings and may not directly apply to your specific farm conditions, pig genetics, or management practices. Dietary decisions should be made in consultation with a veterinarian or animal nutritionist who understands your operation’s specific needs, resources, and goals. The findings represent one study and should be considered alongside other research and practical farm experience. Always follow label directions for any feed additives and consult with feed manufacturers about proper implementation of dietary changes.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.