Researchers tested whether pregnant pigs could eat a diet with less protein without harming their babies or their own health. They compared two groups of pigs: one eating normal protein food and one eating food with about 17% less protein (but with added amino acids, which are protein building blocks). The results were encouraging—the pigs eating less protein had just as many healthy babies as the control group, but produced less nitrogen waste that pollutes the environment. This suggests farms could reduce protein use and environmental impact while keeping pigs and their piglets healthy.

The Quick Take

  • What they studied: Whether pregnant pigs could eat food with less protein (without harming their babies) and whether this would reduce environmental pollution from pig farming
  • Who participated: 24 adult female pigs (Landrace × Yorkshire breed) that had been pregnant 4-5 times before, divided into two equal groups of 12 pigs each
  • Key finding: Pigs eating the lower-protein diet (11.30% protein instead of 13.65%) produced significantly less nitrogen waste and had the same number of healthy babies as pigs eating normal protein food
  • What it means for you: If you work in farming or care about reducing agricultural pollution, this suggests farms could use less protein feed without hurting animal health or productivity. However, the lower-protein diet did require adding specific amino acids to work properly.

The Research Details

Scientists divided 24 pregnant pigs into two groups. One group ate standard pig food with 13.65% protein, while the other group ate food with 11.30% protein (but with added amino acids to make up for the difference). Both groups ate the same food while nursing their babies. The researchers measured how much weight the pigs gained, how many piglets were born, how healthy the babies were, and how much nitrogen waste the pigs produced. They also tested the pigs’ blood to measure amino acid levels at different times during pregnancy and nursing.

The study lasted from day 30 of pregnancy until the piglets were weaned (stopped nursing). Researchers collected detailed information about the pigs’ body condition, the piglets’ health and growth, and the amount of nitrogen in the pigs’ waste. They also measured specific amino acids in the blood of both mother pigs and baby piglets.

This research design is important because it tests a real-world farming scenario. Instead of just looking at one thing (like protein levels), the researchers measured multiple outcomes—reproductive success, environmental impact, and nutritional status. This gives a complete picture of whether the lower-protein approach actually works without hidden problems.

This is a controlled experiment with two matched groups, which is a solid research design. The sample size is relatively small (24 pigs total), which means results should be confirmed with larger studies. The researchers measured multiple important outcomes, which strengthens the findings. However, this was conducted in a controlled farm setting, so results might differ in different environments or with different pig breeds.

What the Results Show

The most important finding was that pigs eating the lower-protein diet had just as many healthy babies as pigs eating normal protein food. The number of piglets born alive and their body weights were essentially the same between groups. This is crucial because it shows the lower-protein approach didn’t harm reproduction.

The lower-protein diet significantly reduced nitrogen excretion (waste), which was a major goal of the study. This means farms using this approach would produce less environmental pollution. The pigs eating lower protein also gained less body fat during mid-pregnancy, though this didn’t appear to cause any problems.

Interestingly, the lower-protein diet did change some amino acid levels in the pigs’ blood. Levels of valine, arginine, lysine, and methionine (all important amino acids) were lower in pigs eating the reduced-protein diet. However, because the researchers added these amino acids to the lower-protein food, the levels didn’t drop dangerously low.

Several secondary findings provide additional context. The piglets born to mothers eating lower-protein food had similar organ sizes and development compared to control piglets, suggesting normal development. When piglets were weaned and eating solid food, some amino acid differences appeared in their blood, but these differences were small and didn’t appear to harm their health or growth. The milk produced by mothers on the lower-protein diet had slightly lower amino acid content, but again, this didn’t negatively affect piglet growth.

This research aligns with previous studies suggesting that carefully designed lower-protein diets can reduce environmental impact in livestock farming. However, most previous work focused on whether animals could survive on less protein, not whether they could maintain full reproductive performance. This study goes further by showing that with proper amino acid supplementation, reproductive success doesn’t suffer. The findings support the growing scientific consensus that ‘smart’ protein reduction (using amino acid supplements) is better than simple protein reduction.

The study used only 24 pigs, which is a relatively small number. Results might be different with larger groups or different pig breeds. The study was conducted in a controlled farm setting, so results might not apply to all farming conditions. The researchers only tested one level of protein reduction (from 13.65% to 11.30%), so we don’t know if even lower protein levels would work. Finally, the study only lasted through one pregnancy and nursing cycle, so long-term effects over multiple pregnancies aren’t known.

The Bottom Line

Based on this research, farms may consider using lower-protein diets (around 11.30% protein) during mid-to-late pregnancy in pigs, provided they add specific amino acids (arginine, valine, lysine, methionine, tryptophan, and threonine). This approach appears safe and effective for maintaining healthy reproduction while reducing environmental pollution. However, this recommendation should be confirmed with larger studies and tested in different farming conditions before widespread adoption. Confidence level: Moderate—the results are promising but based on a relatively small study.

This research is most relevant to pig farmers, agricultural scientists, and environmental advocates concerned about farming’s ecological impact. It’s also important for feed manufacturers who develop pig nutrition products. General consumers might care because it suggests a way to make pig farming more environmentally friendly. People with no connection to pig farming probably don’t need to change their behavior based on this study.

If farms implemented this lower-protein diet strategy, environmental benefits (reduced nitrogen pollution) would appear immediately in the waste produced. However, to see whether the approach works long-term, farms would need to monitor multiple breeding cycles (at least 1-2 years) to ensure reproductive performance stays consistent.

Want to Apply This Research?

  • For farm managers using a nutrition app: Track weekly nitrogen excretion levels (measured in grams per pig per day) and compare to baseline. Set a goal to reduce nitrogen excretion by 10-15% while monitoring that piglet birth rates and weights remain stable or improve.
  • If managing a pig farm: Gradually transition pregnant pigs to the lower-protein diet (11.30% crude protein) starting at day 30 of gestation, ensuring that the feed includes supplemental amino acids (arginine, valine, lysine, methionine, tryptophan, and threonine). Monitor the first two breeding cycles closely before full implementation.
  • Track three key metrics monthly: (1) Number of piglets born alive per sow, (2) Average piglet birth weight, and (3) Estimated nitrogen excretion. If all three metrics remain stable or improve, the lower-protein diet is working. If piglet numbers or weights drop, return to standard protein levels and consult a nutritionist.

This research applies specifically to pig farming and nutrition. It should not be applied to other animals or species without additional research. Farmers considering dietary changes should consult with a veterinarian or animal nutritionist before implementation, as individual farm conditions, pig breeds, and management practices may affect results. This study was conducted in a controlled research setting and results may vary in commercial farming environments. The findings represent one study and should be confirmed by additional research before making major farm management changes. Always follow local regulations regarding animal nutrition and environmental protection.