Research shows that pigs fed higher-energy diets grow faster and convert feed to body weight more efficiently, with the magnitude of improvement depending on maintaining the right balance between lysine and energy. According to Gram Research analysis of 91 pig farming experiments, when farmers increased dietary energy while keeping the lysine-to-energy ratio constant, pigs showed greater improvements in growth performance compared to simply increasing energy alone. The study also found that higher energy diets increased backfat and loin muscle thickness but decreased lean meat percentage.
Scientists analyzed 91 pig farming studies to understand how the energy content in feed affects how fast pigs grow and the quality of meat they produce. Gram Research analysis shows that when pigs eat feed with more energy, they grow faster and convert feed to body weight more efficiently. The study also found that the balance between a specific amino acid called lysine and energy in the feed matters a lot. Different databases used to calculate feed nutrients gave slightly different predictions, but all agreed on the main finding: more dietary energy means better growth and changes in meat characteristics like fat and muscle content.
Key Statistics
A meta-analysis of 91 pig farming experiments published in 2026 found that average daily gain and feed efficiency improved as dietary net energy increased across all four nutrient databases evaluated.
Research reviewed by Gram shows that maintaining a constant lysine-to-energy ratio produced greater changes in pig growth performance compared to keeping lysine levels constant while increasing energy.
The 2026 meta-analysis found that loin depth increased in response to higher dietary energy, with the greatest improvements at lower energy levels and responses plateauing at high energy levels across all nutrient databases.
The Quick Take
- What they studied: How the energy content and nutrient balance in pig feed affects how quickly pigs grow and what their meat looks like when they’re ready for processing.
- Who participated: Data from 91 different pig farming experiments conducted across multiple studies, all involving grow-finish pigs (pigs being raised to market weight) fed different types of diets.
- Key finding: Pigs fed higher-energy diets grew faster and converted feed to body weight more efficiently. The relationship between lysine (an amino acid) and energy in the feed significantly influenced how much pigs benefited from extra energy.
- What it means for you: Pig farmers can use these findings to better predict how changes to feed composition will affect pig growth rates and meat quality. This helps them make more informed decisions about feed formulation to optimize production efficiency. However, results may vary depending on which nutrient database they use for calculations.
The Research Details
Researchers conducted a meta-analysis, which means they collected data from 91 separate pig farming experiments and analyzed them together as one large study. Each experiment tested different feed formulations with varying amounts of energy and nutrients. The scientists used mathematical models to identify which nutrients most strongly predicted pig growth and meat characteristics.
They compared nutrient values from four different databases (NRC, CVB, INRA, and Rostagno) that farmers and nutritionists use to calculate what’s actually in pig feed. This comparison was important because different databases sometimes give different nutrient values for the same ingredients, which could affect predictions.
The researchers used a statistical method called stepwise selection to build prediction models. They tested whether nutrients had linear effects (straight-line relationships), curved effects, or interactive effects (where one nutrient’s impact depends on another nutrient’s level).
This research matters because pig farming is a major food production industry, and small improvements in feed efficiency can save farmers money and reduce environmental impact. By understanding exactly how feed energy and nutrient balance affect pig growth, farmers can formulate feeds more precisely. The comparison of different nutrient databases is especially important because farmers in different countries use different databases, and this study shows whether those differences actually matter for predictions.
This is a meta-analysis combining data from 91 experiments, which is a strong research design that shows patterns across many studies rather than relying on a single experiment. The use of multiple nutrient databases adds credibility by testing whether findings hold up regardless of which database is used. However, the study doesn’t specify how many individual pigs were involved across all 91 experiments, and the quality depends on the quality of the original experiments included in the analysis.
What the Results Show
The most important finding was consistent across all four nutrient databases: when pigs ate feed with more energy, they grew faster (higher average daily gain) and used feed more efficiently (better gain-to-feed ratio). This makes intuitive sense because energy is the fuel pigs use for growth.
The study also found that maintaining the right balance between lysine and energy was crucial. When farmers kept the lysine-to-energy ratio constant while increasing energy, pigs responded with even better growth. When they increased energy without adjusting lysine levels, the growth improvement was smaller. This suggests that lysine becomes a limiting factor if energy increases without enough lysine to match.
For meat quality, higher dietary energy led to pigs having more backfat (fat under the skin) and thicker loin muscles, but less overall lean meat percentage. The dressing percentage (the proportion of the pig that becomes usable meat) also increased with dietary energy, though the effect varied depending on which nutrient database was used.
The study revealed important differences between the four nutrient databases. The Rostagno database appeared to overestimate growth when diets contained high levels of fiber. The different databases also predicted different magnitudes of change in dressing percentage when the lysine-to-energy ratio wasn’t maintained. For loin depth (muscle thickness), all databases predicted a curved response to energy: improvements were greatest at low energy levels and then plateaued at high energy levels, meaning extra energy had less benefit once pigs were already getting plenty.
This research builds on decades of pig nutrition science by creating unified prediction models across multiple databases and studies. Previous research established that energy and lysine are important for pig growth, but this meta-analysis quantifies exactly how much each nutrient matters and shows that the lysine-to-energy ratio is more predictive than lysine alone. The finding that different databases give somewhat different predictions is new and important for the industry.
The study doesn’t report the total number of individual pigs across all 91 experiments, making it hard to assess the statistical power. The analysis is limited to grow-finish pigs and may not apply to younger or breeding pigs. The models are based on data that may be several years old, and modern pig genetics and farming practices may have changed. Additionally, the study only examined the nutrients included in the models; other factors like feed additives, health status, and environmental conditions weren’t considered.
The Bottom Line
Pig farmers should consider using these models to optimize feed formulation by ensuring adequate energy while maintaining appropriate lysine-to-energy ratios. The models can help predict how changes to feed composition will affect both growth performance and meat quality. Farmers should be aware that predictions may vary slightly depending on which nutrient database they use, but the overall patterns are consistent. Confidence in these recommendations is moderate to high for the primary findings about energy and growth, and moderate for specific predictions about meat quality.
Pig farmers and feed manufacturers should care most about these findings, as they directly affect production decisions. Veterinarians and animal nutritionists advising farms will find this useful for feed formulation. Researchers studying pig nutrition will appreciate the comparison of different nutrient databases. This research is less relevant for people who simply consume pork, though it indirectly affects meat availability and price.
Changes in feed formulation would affect pig growth within weeks, as pigs are typically raised for 4 to 6 months from weaning to market weight. Farmers would see measurable differences in growth rates and feed efficiency within the first few weeks of feeding a reformulated diet. Changes in meat quality characteristics would be visible at processing time, typically 4 to 6 months after diet changes begin.
Frequently Asked Questions
How does feed energy affect how fast pigs grow?
Higher energy feed makes pigs grow faster and use feed more efficiently. The 2026 meta-analysis of 91 experiments found that average daily gain and feed conversion improved consistently as dietary energy increased, regardless of which nutrient database was used for calculations.
Why is the lysine to energy ratio important in pig feed?
Lysine is an amino acid pigs need for muscle growth, and it works together with energy. When farmers increased energy while maintaining the lysine-to-energy ratio, pigs grew better than when energy increased without adjusting lysine, showing that the balance between these nutrients matters.
Does higher energy feed make pigs fatter or more muscular?
Higher energy feed increases both fat and muscle, but increases fat more than lean meat. The study found that backfat depth and loin muscle thickness increased with dietary energy, while the percentage of lean meat decreased.
Do different nutrient databases give the same predictions for pig growth?
All four databases (NRC, CVB, INRA, and Rostagno) agreed that higher energy improves growth, but they predicted slightly different magnitudes of change. The Rostagno database tended to overestimate growth when diets contained high fiber levels.
How quickly would farmers see results from changing pig feed formulation?
Farmers would see measurable differences in growth rates and feed efficiency within the first few weeks of feeding a reformulated diet. Full effects on meat quality would be visible at processing time, typically 4 to 6 months after diet changes begin.
Want to Apply This Research?
- Track daily feed intake and weekly weight gain for a group of pigs on a specific feed formulation, then compare actual results to model predictions. Record the energy content and lysine levels of the feed used.
- Use the prediction models to adjust feed formulation by increasing energy content while maintaining or adjusting the lysine-to-energy ratio based on desired outcomes. Test the new formulation on a subset of pigs and monitor growth performance against baseline data.
- Establish a baseline of current growth performance and feed efficiency with existing feed formulations. After implementing changes based on the models, track average daily gain and feed conversion ratio monthly. Compare actual results to model predictions to validate the models’ accuracy for your specific operation.
This research applies specifically to grow-finish pigs and may not apply to other animal species or different pig production stages. The models are based on historical data and may not account for changes in modern pig genetics, farming practices, or environmental conditions. Farmers should consult with animal nutritionists before making significant changes to feed formulations, as individual farm conditions, pig genetics, and health status can affect results. This information is for educational purposes and should not replace professional veterinary or nutritional advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.