South Africa Wine Technical Yearbook 2025

JANUARY/FEBRUARY

JACKIELOU DL, PIXABAY

Grape marc – a game-changer for greener dairies? By Lucinda Heyns

In an attempt to reduce the dairy industry’s carbon footprint, can grape marc be a sustainable feed alternative? Introduction The dairy industry plays a crucial role in feeding the world’s growing population and supplying foods such as milk, cheese and yoghurt. However, the industry also has a significant carbon footprint, mainly due to methane emissions from dairy cows. Methane, a potent greenhouse gas, is a by-product of enteric fermentation, a digestive process in ruminant animals like cows. As global concerns about climate change intensify, reducing methane emissions from dairy cows has become an important consideration. Researchers have been exploring various ways to lessen the environmental impact of dairy farming in recent years. One promising strategy is using agricultural by-products as feed supplements for dairy cows, which not only helps reduce methane emissions, but also provides a cost-effective and sustainable alternative to traditional feeds. One such by product is grape marc, the leftover skins, seeds and stems from wine production. Globally, about nine million tonnes of grape marc are produced each year, but its value beyond compost is often underutilised. While grape marc may seem like a waste product, in this article, based on a research project conducted in Australia, we explore the potential of grape marc as a feed supplement in the dairy industry. The project focused on its effects on milk production and methane emissions. Agricultural by-products – a sustainable feed option Using agricultural by-products as feed is not a new concept, but it is gaining momentum as the need for more

sustainable farming practices grows. By-products from industries such as wine, oilseeds and cereals are typically rich in fat and other nutrients that are beneficial for ruminants. Studies have shown that by-products containing condensed tannins and fats can reduce enteric methane production in dairy cows, making them an attractive option for reducing the dairy industry’s environmental impact. One of the most exciting aspects of using by-products like grape marc is their potential to improve milk’s nutritional profile. Grape marc, for instance, is rich in long-chain fatty acids such as linolenic acid, known for its health benefits in humans. Feeding cows a diet that includes grape marc can lead to milk enriched with these beneficial fatty acids, offering an added nutritional bonus to consumers. The Australian dairy industry and feed shortages Another benefit of exploring agricultural by-products to supplement animal diets is that it can be a solution for farmers when they experience feed shortages during droughts. Australia’s dairy farming system relies heavily on pasture, primarily perennial ryegrass, which is supplemented with cereal grains. However, during dry summer months or periods of drought, pasture availability becomes limited, and cereal grains can become expensive or hard to come by. Grape marc presents a potential solution as an alternative feed source that can help to maintain milk production and animal health during feed shortages. The grape marc experiment To explore the potential of grape marc as a feed supplement, researchers conducted an experiment at the Agriculture Victoria Research Ellinbank Dairy Centre in Victoria, Australia. The aim was to determine and compare the effects of red and

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TECHNICAL YEARBOOK 2025