Grape stalks as a sustainable feed supplement for dairy cows: a preliminary in vivo study on milk microbiota and cheese quality

Grape stalks are the woody stems that remain after grapes are processed for winemaking. In the Trentino-Alto Adige region, large amounts of these materials are produced every year, and their disposal represents a cost for wineries. Instead of treating grape stalks as waste, they could be used as a valuable resource for dairy farms. In this study, we explored whether adding a small amount of grape stalks to the daily diet of dairy cows could influence milk composition and the cheese made from that milk. A seven-week alternating design was applied to three cows, which were fed either their usual diet or the same diet supplemented with grape stalks in alternating weeks. Milk was collected weekly, and small cheeses were produced to examine possible changes in quality, bacterial composition, and aroma. We found that feeding grape stalks did not negatively affect milk quality or safety. Some natural bacterial groups in the milk decreased when cows received grape stalks, and the cheeses showed small but consistent differences in natural plant compounds and in smell and flavor. These preliminary findings suggest that grape stalks could become a valuable and sustainable resource for dairy farms, supporting local circular economy practices and reducing waste from winemaking