Researchers tested whether grape pomace—a leftover material from wine production—could improve the health of sheep raised for meat. They fed 18 sheep different amounts of grape pomace mixed into their regular feed for two months. The results showed that adding grape pomace didn’t slow down the sheep’s growth, but it did make their blood healthier, increased protective compounds in their bodies, and improved the quality of their muscle meat. The grape pomace also appeared to reduce some harmful bacteria in the sheep’s stomachs. This suggests that grape pomace could be a useful, sustainable way to improve farm animal health while using a product that would otherwise be wasted.

The Quick Take

  • What they studied: Whether adding grape pomace (a leftover from making wine) to sheep feed would improve their health, growth, and meat quality
  • Who participated: 18 young male sheep that were a mix of two breeds (Dorper and Hu sheep), all raised under the same conditions for 60 days
  • Key finding: Sheep that ate grape pomace grew just as well as sheep on regular feed, but had stronger immune systems, better antioxidant protection (natural defense against cell damage), and higher quality muscle protein. They also had fewer harmful bacteria in their digestive systems.
  • What it means for you: If you eat lamb or mutton, this research suggests that farmers could use grape pomace to produce healthier, higher-quality meat without affecting how much meat the animal produces. This is especially useful because it recycles a waste product from wine-making. However, this study was done on sheep, so results may not directly apply to other animals or humans.

The Research Details

Scientists divided 18 young sheep into three equal groups. One group ate regular feed with no grape pomace (the control group), while the other two groups ate feed mixed with either 15% or 20% grape pomace. All sheep ate the same type of food otherwise and lived in the same conditions. The researchers fed them this way for 60 days (about 2 months), then measured how much weight they gained, tested their blood, examined their muscle tissue, and analyzed the bacteria living in their stomachs.

This type of study is called a controlled experiment because the researchers carefully controlled what each group ate and measured the differences between groups. By having a control group that ate no grape pomace, the scientists could tell whether any changes were actually caused by the grape pomace and not by something else.

The researchers looked at several different measurements: how fast the sheep grew, chemicals in their blood that show health status, the types of proteins in their muscles, and the types of bacteria in their digestive systems. This gave them a complete picture of how grape pomace affected the sheep’s overall health.

This research approach is important because it tests whether a waste product from the wine industry could be useful in farming. By measuring multiple aspects of sheep health—not just growth, but also blood chemistry and gut bacteria—the scientists could see the full picture of how grape pomace affects animals. This matters because farmers are always looking for ways to improve animal health while using sustainable materials and reducing waste.

This study has some strengths: it used a control group for comparison, measured multiple health markers, and tested two different amounts of grape pomace to see if more was better. However, the study only included 18 sheep, which is a relatively small number. The study lasted 60 days, which is long enough to see some effects but might not show long-term impacts. The research was published in a peer-reviewed scientific journal, meaning other experts reviewed it before publication. The study was done on one specific type of sheep, so results might be different in other sheep breeds or farm animals.

What the Results Show

The most important finding was that adding grape pomace to sheep feed did not slow down their growth or weight gain. This is crucial because farmers need animals to grow well to make farming profitable. Sheep that ate 15% or 20% grape pomace gained weight at the same rate as sheep eating regular feed.

Beyond growth, grape pomace improved several health markers in the sheep’s blood. The sheep eating grape pomace had higher levels of total protein in their blood, which is a sign of good nutrition and health. More importantly, they had significantly higher antioxidant capacity, which means their bodies had better natural defenses against cell damage. Think of antioxidants like a shield that protects your cells from harm.

When the researchers examined the muscle tissue (the meat), they found that sheep eating grape pomace had higher levels of essential amino acids. Amino acids are the building blocks of protein, and essential amino acids are the ones animals can’t make themselves and must get from food. Having more of these in the meat means the meat is more nutritious.

Finally, the grape pomace changed the bacteria living in the sheep’s stomachs. While the total number of different bacteria types stayed about the same, certain harmful bacteria (specifically one called Treponema) became less common in sheep eating grape pomace. This suggests the grape pomace has a protective effect against some bad bacteria.

The study found that the effects were similar whether sheep ate 15% or 20% grape pomace, suggesting that 15% might be enough to get the benefits without needing to add more. The researchers also noted that the grape pomace appeared to work by providing antioxidant compounds naturally present in grapes, which protected the sheep’s cells from damage. The reduction in harmful bacteria suggests that grape pomace might help prevent certain digestive problems, though the study didn’t directly measure disease prevention.

Previous research has shown that grape byproducts contain beneficial compounds called polyphenols that have antioxidant properties. This study confirms that these compounds actually work in living animals, not just in test tubes. The finding that grape pomace reduces harmful bacteria is consistent with other research showing that plant-based compounds can influence gut bacteria in positive ways. However, most previous studies on grape byproducts were done in laboratories or with different animals, so this study adds important evidence that grape pomace works in sheep specifically.

The study only included 18 sheep, which is a small number. Larger studies with more animals would give more reliable results. The study lasted only 60 days, so we don’t know if the benefits continue over longer periods or if there might be any long-term effects. The research was done on one specific type of sheep (Dorper × Hu hybrids), so results might be different in other sheep breeds. The study didn’t measure whether the improved health actually led to fewer diseases or better survival rates. Finally, the study was done in a controlled farm setting, so results might be different in real-world farming conditions where sheep face more stress and disease exposure.

The Bottom Line

Based on this research, farmers could consider adding 15% grape pomace to sheep feed as a way to improve meat quality and animal health without affecting growth rates. The evidence is moderate because the study was small and only lasted 60 days. If you’re a farmer, it would be worth trying this on a small scale to see if it works in your specific situation. If you’re a consumer, this research suggests that lamb from sheep fed grape pomace might be slightly more nutritious, though the difference would likely be small.

Sheep farmers and livestock producers should care about this research because it offers a way to improve animal health using a waste product, which could save money and help the environment. Wine producers might be interested because it gives them a use for their byproducts. Consumers who care about animal welfare and sustainable farming should care because this approach improves animal health without using medications. People with specific dietary needs for high-quality protein might benefit from meat produced this way. However, this research is specific to sheep, so it may not apply to cattle, pigs, or poultry without further testing.

The benefits measured in this study appeared within 60 days of feeding grape pomace, so farmers could expect to see improvements in blood health markers relatively quickly. However, the effects on meat quality and muscle composition would take the full 60 days to develop. Long-term benefits and whether these improvements continue beyond 60 days are unknown and would require longer studies.

Want to Apply This Research?

  • If you’re a farmer using this approach, track weekly weight gain of your sheep and record the date you started adding grape pomace to their feed. Compare weight gain rates between your grape pomace group and your control group to see if the results match this study.
  • If you manage livestock, consider sourcing grape pomace from local wineries and gradually introduce it to your feed mix at 15% concentration. Start with a small group of animals to test the approach before scaling up to your whole herd.
  • Over a 60-day period, monitor your animals’ appearance, energy levels, and growth rates weekly. Keep records of feed costs and compare them to any savings from using a byproduct. After 60 days, have your veterinarian do a blood test to check if antioxidant levels have improved, similar to what the researchers measured.

This research was conducted on sheep and may not apply to other animals or humans. The study was small (18 animals) and lasted only 60 days, so results should be considered preliminary. Before making changes to livestock feeding practices, consult with a veterinarian or animal nutritionist familiar with your specific animals and farming conditions. This research is not a substitute for professional veterinary or nutritional advice. Individual results may vary based on animal breed, age, health status, and farming conditions. Always follow food safety guidelines when sourcing and handling grape pomace for animal feed.