Research shows that feeding pigs up to 40% leftover sugary food products doesn’t significantly harm meat quality or final growth rates, but does reduce body fat deposits and change fat composition. A 2026 study of 36 pigs found that those eating 40% food waste products developed thinner fat layers and more efficient feed conversion in their final growth phase, suggesting food waste can be safely incorporated into pig diets to reduce costs and environmental impact.
Researchers tested whether feeding pigs food industry leftovers (like expired or surplus sugary products) could work as a cheaper alternative to regular feed. They gave 36 pigs different amounts of these leftover foods—none, 20%, or 40%—and tracked how well the pigs grew, how they ate, and the quality of their meat. According to Gram Research analysis, using up to 40% leftover sugary foods didn’t hurt meat quality much, but it did change how much fat the pigs stored and what type of fat they developed. This matters because it could help reduce food waste while keeping pork production sustainable.
Key Statistics
A 2026 research study of 36 pigs found that including 40% leftover sugary food products in pig feed reduced body fat content and improved feed conversion efficiency in the final growth phase without significantly affecting meat quality.
According to research reviewed by Gram, pigs fed 20% food waste products showed the most efficient feeding behavior, spending the least time at feeders while consuming feed faster than control pigs.
A 2026 pig nutrition study found that sugary food waste inclusion altered fatty acid composition, increasing monounsaturated fats (considered healthier) while decreasing polyunsaturated fats in pig adipose tissue.
The Quick Take
- What they studied: Whether feeding pigs leftover sugary food products (instead of regular grain-based feed) affects how fast they grow, how they behave while eating, and the quality of meat they produce.
- Who participated: 36 castrated male pigs raised from about 44 pounds to 319 pounds over roughly 6.5 months, divided into three groups receiving different amounts of leftover food.
- Key finding: Pigs eating up to 40% leftover sugary foods grew similarly to control pigs but developed less body fat and different fat composition, with only minor changes to meat quality.
- What it means for you: Food waste reduction in agriculture is possible without sacrificing meat quality, though this research is specific to pigs and doesn’t directly affect human consumers. Farmers might save money using leftover foods as feed, but more research is needed on long-term effects and safety.
The Research Details
Researchers divided 36 pigs into three equal groups and fed them different diets over three growth phases (from 44-319 pounds). One group ate regular feed (control), one ate feed with 20% leftover sugary food products mixed in, and one ate feed with 40% leftover products. The pigs had automatic feeders that tracked exactly how much each pig ate at each meal. When the pigs reached about 319 pounds at roughly 191 days old, they were slaughtered and researchers measured their body composition, meat quality, and fat characteristics.
This approach allowed scientists to see how the leftover foods affected growth at different life stages (young pigs, medium pigs, and nearly full-grown pigs). By using automatic feeders, they could measure not just total food eaten but also eating behavior—like how long pigs spent at the feeder and how often they visited.
The researchers used statistical analysis to look for patterns, testing whether changes happened gradually as more leftover food was added (linear effects). They also accounted for the fact that pigs from the same litter might be more similar to each other than to pigs from different litters.
This research design is important because it tests a real-world solution to food waste in a controlled way. By measuring multiple outcomes (growth, behavior, meat quality, fat composition), researchers could see the full picture of whether this practice is safe and practical. The automatic feeders provided precise data that wouldn’t be possible with manual observation.
Strengths: The study used a controlled experimental design with clear treatment groups and measured multiple important outcomes. The automatic feeders provided objective data on feeding behavior. Limitations: The sample size was relatively small (36 pigs total), which limits how broadly the findings apply. The study only tested one type of leftover food product (sugary items), so results may not apply to other types of food waste. The study was conducted in a single facility, so results might differ in other environments. No information was provided about the specific composition of the leftover foods used, making it harder to understand exactly what the pigs were eating.
What the Results Show
During the early growth phase (44-132 pounds), pigs eating more leftover sugary food ate less and gained weight more slowly compared to control pigs. However, during the later growth phases (132-220 pounds and 220-319 pounds), the differences in weight gain disappeared—all pigs grew at similar rates regardless of diet. Interestingly, in the final growth phase, pigs eating the leftover foods actually converted feed to body weight more efficiently, meaning they needed less total food to gain the same amount of weight.
When researchers examined the pigs’ bodies after slaughter, they found that pigs eating leftover sugary foods had less total body fat and more protein and water in their bodies compared to control pigs. The backfat (fat layer under the skin) was noticeably thinner in pigs eating the leftover foods. These changes suggest that the leftover foods altered how pigs stored energy in their bodies.
Meat quality measurements showed only minor differences. The pH of the meat (a measure of acidity) was slightly lower in pigs eating leftover foods, and the color was slightly different, but these changes were small and unlikely to matter to consumers. The composition of fatty acids in the fat tissue did change—pigs eating leftover foods had more monounsaturated fats (considered healthier) and fewer polyunsaturated fats.
Feeding behavior changed in interesting ways during the final growth phase. Pigs eating 20% leftover food spent the least time at the feeder but ate faster (more feed per minute) and visited the feeder less frequently. This suggests they were more efficient eaters. Pigs eating 40% leftover food showed different behavior, visiting the feeder more often but spending more time there overall. These behavioral differences didn’t affect overall growth but show that diet composition influences how pigs approach eating.
This study adds to a growing body of research on using food waste as animal feed. Previous research has shown that various food industry byproducts can be used in livestock diets, but most studies focus on nutritional outcomes rather than detailed behavior and fat composition changes. This research is notable for its detailed tracking of eating behavior through automatic feeders and its comprehensive analysis of body composition and fatty acid profiles. The finding that meat quality remained largely unchanged aligns with other studies suggesting that food waste products can be incorporated into animal diets without major quality penalties.
The study only included 36 pigs, which is a relatively small number for drawing broad conclusions. All pigs were the same sex (castrated males) and from the same genetic background, so results may not apply to female pigs or different breeds. The study only tested sugary leftover foods, so results don’t tell us about other types of food waste. The researchers didn’t provide detailed information about the exact composition of the leftover foods, making it difficult to understand which components caused the observed effects. The study was conducted in a single facility under controlled conditions, so real-world results on different farms might differ. Finally, the study didn’t examine potential safety concerns like contamination or long-term health effects of eating food waste products.
The Bottom Line
For farmers and feed manufacturers: Using up to 40% sugary food waste products in pig feed appears safe and may improve feed efficiency in later growth stages, potentially reducing costs. However, more research is needed on safety, consistency of leftover food composition, and effects on different pig types. For consumers: This research doesn’t directly affect food safety or quality of pork products, as meat quality remained largely unchanged. For policymakers: This research supports exploring food waste reduction in agriculture, but regulations should ensure that leftover foods are properly screened for safety before use as animal feed.
Pig farmers and feed manufacturers interested in reducing costs and food waste should pay attention to these findings. Environmental advocates concerned with food waste reduction may find this encouraging. Consumers interested in sustainable food production might appreciate that meat can be produced using food waste. People with specific concerns about meat quality or fatty acid composition should note that changes were minimal. This research is specific to pigs and doesn’t directly apply to other livestock or to human nutrition.
Changes in pig growth and feed efficiency appeared within weeks during the early growth phase, with the most noticeable effects in the first 88 pounds of growth. Changes in body fat composition developed gradually over the entire 6.5-month growth period. If a farmer switched to using leftover foods, they would likely see cost savings immediately, but the full effects on body composition would only be apparent at slaughter.
Frequently Asked Questions
Is it safe to feed pigs leftover food from factories?
This study suggests sugary food waste can be safely used up to 40% in pig diets without harming meat quality. However, researchers didn’t test for contamination or long-term safety effects, so proper screening and regulations are essential before widespread use.
Does feeding pigs food waste change the quality of pork meat?
Meat quality remained largely unchanged in pigs eating up to 40% food waste products. Only minor differences in pH and color appeared, which are unlikely to affect consumer experience or food safety.
Can using food waste as pig feed save farmers money?
This study suggests potential cost savings, especially since pigs eating food waste showed better feed efficiency in later growth stages. However, actual savings depend on local food waste availability, processing costs, and feed prices in your area.
How much food waste can you safely add to pig feed?
This study tested up to 40% inclusion of sugary food waste products without major problems. However, results may vary with different types of food waste, so farmers should start with lower percentages and monitor their specific pigs’ performance.
Does feeding pigs food waste affect how fast they grow?
In early growth stages, pigs eating more food waste grew slightly slower. However, by the final growth phase, all pigs reached similar weights, and those eating food waste actually converted feed to body weight more efficiently.
Want to Apply This Research?
- Track weekly feed costs and feed conversion ratio (pounds of feed needed per pound of weight gain) to monitor whether incorporating food waste products actually saves money while maintaining growth rates.
- For farmers using the app: Log the percentage of food waste products in your feed mix weekly and correlate it with your pigs’ growth rates and feed efficiency metrics to find the optimal balance for your operation.
- Establish a baseline of your current feed costs and growth performance, then gradually introduce food waste products while tracking these metrics monthly. Monitor carcass quality at slaughter to ensure meat quality remains acceptable, and adjust percentages based on your results.
This research is specific to pig nutrition and does not directly apply to human food safety or nutrition. While the study suggests that food waste products can be incorporated into pig feed without major quality concerns, proper safety screening and regulatory oversight are essential before implementing this practice. Farmers considering using food waste products should consult with veterinarians and nutritionists to ensure the specific products are safe and appropriate for their operation. This research does not address potential contamination risks, long-term health effects, or applicability to other livestock species. Always follow local regulations regarding the use of food waste in animal feed.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.