South Africa’s wine industry, particularly in the Western Cape, generates significant amounts of grape pomace. This byproduct, which consists of skins, pulp, seeds and stalks, accounts for approximately 20-25% of the crush weight of grapes.
By Dr Bulelani Mazizi, Dr Letlhogonolo Selaledi and Dr Pulane Sebothoma (Nutrition department, Agriculture Research Council – Animal Production)
Utilising grape pomace in poultry and pig feeds presents numerous benefits: it supports a circular bioeconomy, reduces feed costs, minimises agro-industrial waste, and aligns with the sustainability and food security goals of the national Department of Agriculture (DoA).
Grape seeds, a major byproduct of the winemaking process, are an excellent source of bioactive compounds like polyphenols and proteins. These compounds have many applications, including in nutraceutical products, cosmetics, and within the wine industry itself. The presence of these nutritional and bioactive compounds can positively impact the growth performance of monogastric animals by enhancing intestinal health. However, incorporating high levels of grape by-products into their diets can impair growth performance due to anti-nutritional factors. Therefore, it is essential to explore beneficial inclusion levels thoroughly.
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Valorising grape by-products as feed alternatives and intestinal health promoters is crucial for boosting the circular agricultural economy. We must also consider the various bioactive compounds found in grape seeds within the contexts of waste valorisation and green chemistry, such as solvent-free extraction.
The South African wine industry is a cornerstone of our agricultural heritage. Yet, with every bottle produced, a significant byproduct, grape pomace, is created. This presents both a challenge and an opportunity for innovative farmers. With an estimated 300,000 tons generated annually, primarily in the Western Cape, effective utilisation of this material is vital for environmental sustainability and economic resilience in farming. Disposing of this vast volume of pomace poses a significant challenge; in landfills, it can pollute ground and surface water. Its low pH and high levels of antibacterial polyphenols hinder natural biodegradation. While composting is an option, it often lacks economic viability due to nutrient imbalances. The clear solution? Redirect this material from waste to feed.
Don’t let the term “waste” mislead you. Grape pomace is a treasure trove of valuable compounds. Its composition varies by grape variety and processing methods, but it is consistently rich in dietary fiber (up to 85%) and polyphenol antioxidants that remain largely after juicing. These components are integral to its potential as animal feed. Incorporating dried grape pomace into animal diets can provide multifaceted benefits, such as dietary fiber that acts as a prebiotic, promoting beneficial gut bacteria (like Lactobacillus) while suppressing harmful pathogens like E. coli.
This leads to improved gut motility and overall animal health. The powerful antioxidants help broilers manage heat stress and support weaning piglets through a challenging growth phase. Polyphenols can enhance meat stability and shelf life, while in sows, pomace can positively influence the fat profile of pork towards healthier, more stable fats. For laying hens, grape pomace can enhance yolk color and improve egg shelf life. When used strategically, pomace can replace more expensive traditional ingredients like corn or wheat bran, contributing to waste valorisation and reduced feed costs.
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To leverage these benefits safely and effectively, careful management is essential. Fresh pomace is perishable and needs to be adequately dried and stored to prevent mold. Because of anti-nutritional factors like tannins, the inclusion levels of grape pomace must be managed carefully. Recommended rates typically range from 3% to 8% of the total diet, depending on the animal species, age, and production stage. It’s important to introduce pomace gradually into animal rations and monitor their performance and acceptance.
Grape pomace is not just waste; it is a viable, nutrient-rich feed ingredient that can enhance animal health, improve product quality, and bolster farm sustainability. By integrating this local byproduct into livestock diets, South African farmers can tackle environmental challenges, reduce feed costs, and contribute to a more circular agricultural economy, turning the legacy of the vine into a valuable resource for farming.
What is Grape Pomace?
The solid residue left after pressing grapes consists of grape skins, seeds, pulp and small stems. It is rich in polyphenols, such as resveratrol and proanthocyanidins, as well as dietary fibre, unsaturated fatty acids, and natural antioxidants.
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