According to Gram Research analysis of seven studies, probiotics and certain plant extracts can reduce stress behaviors in farm pigs, offering a natural alternative to antibiotics. Probiotics improved exploration and activity in young piglets while reducing stress reactivity in offspring; plant extracts like Moringa reduced aggressive behaviors such as belly nosing. However, researchers emphasize these findings come from limited studies using different methods, requiring more standardized research before widespread farm adoption.
A Gram Research analysis of seven studies examined how natural feed additives affect pig behavior and stress levels on farms. Researchers looked at alternatives to antibiotics that farmers traditionally used to help pigs grow faster. They found that certain additives—like probiotics (beneficial bacteria), plant-based compounds, and amino acids—reduced stress behaviors such as aggression and excessive nosing in pigs. However, the studies were small and used different methods, so scientists say more research is needed before making firm recommendations. This matters because stressed pigs have worse health and welfare, and finding non-antibiotic solutions helps address antibiotic resistance.
Key Statistics
A 2026 systematic review analyzing seven studies found that probiotics improved exploration and activity in weaned piglets and reduced stress reactivity in offspring, suggesting behavioral benefits from this antibiotic alternative.
According to a 2026 systematic review of pig behavior studies, Moringa oleifera plant extract reduced belly nosing—a stress-related behavior—while Passiflora incarnata decreased aggression and biting in weaned piglets.
A 2026 systematic review identified only seven eligible studies out of 1,893 articles examined, highlighting the scarcity of standardized behavioral research on feed additives as antibiotic alternatives in pig production.
Research reviewed by Gram found that L-glutamine increased standing time and novel object exploration in weaned piglets, indicating improved activity levels compared to control groups.
The Quick Take
- What they studied: Whether natural feed additives (like probiotics and plant extracts) can reduce stress behaviors in pigs, replacing antibiotics that farmers have traditionally used
- Who participated: Seven published research studies involving pigs at different life stages (young weaned piglets, adult sows, and their offspring) on farms using various additives
- Key finding: Probiotics improved exploration and activity in young piglets and reduced stress responses in offspring; plant extracts like Moringa reduced aggressive behaviors like belly nosing; however, results varied widely across studies
- What it means for you: If you care about animal welfare or food safety, this research suggests natural alternatives to antibiotics in pig farming may help reduce animal stress. However, farmers should wait for more consistent research before switching all their practices
The Research Details
Researchers conducted a systematic review, which means they searched three major scientific databases (Scopus, PubMed, and Web of Science) for all published studies about how feed additives affect pig behavior. They started with 1,893 articles but carefully selected only seven that met strict quality standards. This approach helps identify what scientists have actually discovered about a topic.
The researchers looked for studies that measured specific pig behaviors like how often they bite each other, how much they explore their environment, how they interact with objects, and whether they show signs of stress or anxiety. They organized their findings by type of additive—organic acids, probiotics (good bacteria), amino acids like L-glutamine, and plant-based compounds.
Because the seven studies used different methods to measure behavior and tested different additives, the researchers couldn’t directly compare results. This is like trying to compare test scores when different schools use different tests—the information is valuable but hard to combine.
This research approach matters because farm animals’ behavior tells us a lot about their health and happiness. When pigs are stressed, they get sick more easily, grow slower, and suffer. Finding natural alternatives to antibiotics is important because overusing antibiotics has created bacteria that antibiotics can’t kill anymore—a serious public health problem. This systematic review pulls together all available evidence to show what works and what doesn’t.
The strength of this review is that researchers followed strict scientific standards and searched multiple databases. The main weakness is that only seven studies met their criteria, meaning very little research has been done on this topic. The studies also measured behavior differently, making it hard to draw firm conclusions. Readers should know this is a ‘snapshot’ of limited evidence, not definitive proof.
What the Results Show
Probiotics (beneficial bacteria added to feed) showed the most promise. In young weaned piglets, probiotics increased exploration and activity—signs of better welfare. In adult sows, probiotics improved their relationship with humans. In offspring, probiotics reduced stress reactivity, meaning the piglets were calmer and less jumpy.
Plant-based additives also showed benefits. Moringa oleifera (a plant extract) reduced belly nosing, which is when stressed pigs repeatedly nose at each other’s bellies—a sign of poor welfare. Passiflora incarnata (passion fruit plant extract) decreased aggression and biting between piglets.
L-glutamine, an amino acid, increased standing time and exploration in young piglets, suggesting improved activity and engagement. Organic acids, however, showed no significant effects on behavior in the studies reviewed.
The researchers emphasized that while these results are encouraging, they come from very few studies with different methods, so the findings should be interpreted carefully.
The review highlighted that stress-related behaviors in pigs—like excessive biting, aggression, and reduced exploration—are major welfare problems on farms. These behaviors often increase when pigs are crowded or in poor conditions. The fact that certain feed additives reduced these behaviors suggests they may help pigs cope with farm stressors. The review also noted that behavioral improvements sometimes appeared in offspring of treated pigs, suggesting benefits might extend across generations.
This is the first systematic review specifically examining how feed additives affect pig behavior as alternatives to antibiotics. Previous research focused mainly on how these additives affect growth and disease resistance, not behavior and welfare. This review fills an important gap by showing that behavioral welfare—not just growth metrics—should be considered when evaluating antibiotic alternatives. The findings align with growing scientific interest in using probiotics and plant compounds for animal welfare.
The biggest limitation is that only seven studies met inclusion criteria out of nearly 1,900 found, showing this is an understudied area. The studies used different additives, different pig breeds, different farm conditions, and different ways of measuring behavior—making direct comparisons impossible. Most studies were small, and some didn’t report important details. The researchers couldn’t determine if observed benefits were due to the additives themselves or other factors. Long-term effects beyond the study period are unknown.
The Bottom Line
Based on current evidence (moderate confidence): Probiotics appear most promising for reducing stress behaviors in pigs and may be worth considering as part of farm management. Plant extracts like Moringa and Passiflora show potential but need more research. Organic acids don’t appear effective based on available studies. Farmers should not rely solely on these additives but combine them with good housing, low stocking density, and proper care. More standardized research is urgently needed before making widespread recommendations.
Pig farmers looking to reduce antibiotic use should pay attention to these findings. Animal welfare advocates and consumers concerned about antibiotic resistance should find this encouraging. Veterinarians advising farms on health management should consider these options. However, people not involved in pig farming don’t need to change behavior based on this research. Consumers can’t directly apply these findings but may benefit if farms adopt these practices.
If a farm switches to probiotics or plant-based additives, behavioral improvements (like reduced aggression) might appear within weeks to a few months, based on the studies reviewed. However, long-term effects over a pig’s entire life aren’t well documented. Benefits may vary depending on farm conditions, pig genetics, and how the additives are used.
Frequently Asked Questions
Can probiotics replace antibiotics in pig farming?
Probiotics show promise for reducing stress behaviors in pigs and may complement antibiotic reduction strategies, but current research is limited. A 2026 review found probiotics improved exploration and reduced stress in piglets, though more studies are needed before they can fully replace antibiotics for disease prevention.
What natural additives reduce aggression in farm pigs?
Plant extracts show the most evidence: Moringa oleifera reduced belly nosing (stress-related aggression), and Passiflora incarnata decreased biting and fighting in weaned piglets, according to a 2026 systematic review of seven studies.
How quickly do feed additives improve pig behavior?
The reviewed studies suggest behavioral improvements like reduced aggression and increased exploration may appear within weeks to months of introducing additives like probiotics or plant extracts, though long-term effects beyond study periods aren’t well documented.
Are organic acids effective for reducing stress in pigs?
A 2026 systematic review found organic acids showed no significant effects on pig behavior compared to control groups, making them less promising than probiotics or plant-based alternatives for stress reduction.
Why is pig behavior important for farm management?
Pig behavior directly indicates welfare and health: stressed pigs show aggression, reduced exploration, and increased illness. A 2026 review emphasizes that behavioral improvements from feed additives suggest better overall animal welfare and potential disease resistance without antibiotics.
Want to Apply This Research?
- For farmers using a farm management app: Track weekly observations of pig behavior (aggression incidents, exploration activity, stress signs) before and after introducing feed additives. Record specific metrics like number of biting incidents per pen or percentage of time pigs spend exploring versus resting.
- Farmers can implement a trial: Select one pig pen to receive probiotic-supplemented feed while keeping a control pen on standard feed. Use the app to log daily behavioral observations (aggression, activity level, social interactions) for 8-12 weeks to see if differences emerge.
- Create a long-term tracking dashboard showing monthly behavioral scores across all pens. Compare pens receiving different additives to identify which works best for your specific farm conditions. Track correlations between additive use and other metrics like illness rates and growth to see if behavioral improvements align with other benefits.
This research summary is for informational purposes only and should not replace professional veterinary advice. Farmers considering changes to pig feed or management should consult with a veterinarian or animal nutrition specialist familiar with their specific operation. The findings in this systematic review are based on limited studies with varying methods; individual results may differ. This article does not constitute medical or veterinary advice for animals or humans.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.