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 white grape marc on milk production and methane emissions in dairy cows. The composition of red and white grape marc differs, because of the difference in the winemaking processes, which is why both were tested. The experiment was carried out following strict animal welfare guidelines.
Thirty-two Holstein dairy cows in early lactation were divided into three groups. All cows had a baseline diet of 15.0 kg of dry matter (DM) from freshly harvested perennial ryegrass and 5.2 kg of a concentrate mix.
- The control group was fed the baseline diet.
- In the second group, 5 kg of ryegrass DM was replaced with 5 kg DM of red grape marc (RGM).
- In the third group, 5 kg of ryegrass DM was replaced with 5 kg DM of white grape marc (WGM).
A Holstein dairy cow (JackieLou DL, Pixabay).
Both red and white grape marc used in the experiment contained the skins and seeds of the grapes and had undergone a crimping process. Crimping involves crushing the seeds and removing the stalks to improve digestibility and energy availability for the cows. The grape marc was stored in airtight bags to prevent spoilage.
The impact on milk production
The experiment showed that substituting part of the cows’ ryegrass intake with grape marc – whether red or white – had a negative effect on milk production. Milk yields decreased by approximately 10% for cows fed RGM and WGM diets compared to those on the control diet. This reduction in milk output can be attributed to the lower metabolisable energy content in grape marc compared to perennial ryegrass.
Despite the drop in milk yield, there were some notable differences between the effects of red versus white grape marc. Cows fed the RGM diet had a lower milk fat concentration than those on the control and WGM diets. However, red grape marc also resulted in higher concentrations of beneficial fatty acids in the milk, suggesting that it may offer superior nutritional benefits compared to white grape marc.
The impact on methane emissions
While milk production suffered, the study found that grape marc positively affected methane emissions. Both RGM and WGM diets led to a 15% reduction in methane emissions compared to the control group. This reduction is primarily due to the high fat and lignin content in grape marc, which alters the fermentation process in the cow’s rumen. Grape marc contains high levels of lignin, a fibrous component poorly fermented in the cow’s rumen. In addition, lignin can bind to carbohydrates, making them less accessible to the digestive enzymes, resulting in reduced fermentation of carbohydrates and, hence, a reduction in ruminal methane production.
The trade-off – sustainability versus milk production
The findings of this study highlight the trade-off between reducing methane emissions and maintaining milk production. While grape marc effectively cuts methane output, the lower energy content of this agricultural by-product leads to decreased milk yields, which may present a challenge for dairy farmers. From a sustainability standpoint, the use of grape marc aligns with efforts to reduce the dairy industry’s carbon footprint. However, for dairy farmers, maintaining milk production is equally important, as it directly affects their income.
Challenges and considerations
While the study results are promising, there are some challenges to consider before grape marc becomes a staple in dairy cow diets. One issue is the variability in the nutritional composition of grape marc, which can depend on factors such as grape variety, winemaking processes and regional differences. Ensuring consistent quality and nutritional content will be essential for widespread adoption. Another consideration is the potential for grape marc to introduce residues from pesticides or other chemicals used in grape cultivation. Strict monitoring and regulation would be necessary to ensure that grape marc is safe for animal consumption and does not pose any risks to food safety.
A step toward sustainability in future dairy farming
As the dairy industry faces increasing pressure to reduce its environmental impact, agricultural by-products like grape marc offer a promising solution. The Ellinbank experiment demonstrated that feeding grape marc to dairy cows can significantly reduce methane emissions, contributing to a more sustainable farming model. It can also be hugely beneficial during periods of drought. Additionally, the ability of grape marc to enrich milk with beneficial fatty acids presents an added health benefit for consumers. However, it may not be a one-size-fits-all solution. The trade-off between methane reduction and milk production must be strategically managed to ensure farmers can maintain their livelihoods while adopting more environmentally friendly practices.
Grape marc could play a crucial role in helping the dairy industry transition to a more sustainable future. By integrating this waste product into animal feed, the industry can reduce reliance on traditional feed sources, lower its carbon footprint, and contribute to the global effort to combat climate change. Further research is needed to optimise the use of grape marc and explore ways to improve its nutritional value.
Reference
Moate, P.J.; Jacobs, J.L.; Hixson, J.L.; Deighton, M.H.; Hannah, M.C.; Morris, G.L.; Ribaux, B.E.; Wales, W.J.; Williams, S.R.O. Effects of Feeding either Red or White Grape Marc on Milk Production and Methane Emissions from Early-Lactation Dairy Cows. Animals 2020, 10, 976. https://doi.org/10.3390/ani10060976.
For more information, contact Lucinda Heyns at lucindaheyns@gmail.com.
Click here to get your copy of WineLand Magazine.
