Potential of Baled Silage to Preserve White Grape Pomace for Ruminant Feeding

The use of agro-industrial by-products in animal feed represents a useful alternative to enhance the sustainability of the agri-food chain. Grape pomace represents an environmental problem mainly for wine-producing countries. Because of the high water content and the seasonality of this feedstuff, ensiling might be a technology to preserve its nutritional quality for a long time, and this must be considered and studied on a commercial scale. This study aimed to characterise the ensiling process of white grape pomace, evaluate its suitability for inclusion in the ruminant diet and compare its shelf life to untreated storage conditions. White grape pomace silos were made with baled silage (300 kg approx.). Samples were analysed at days 0, 7, 14, 35, 60 and 180 of conservation to determine microbial populations, fermentation metabolites, nutritional components and bioactive properties. The collected data were analysed using a general linear model, considering the effect of the treatment, sampling days and their interaction (Proc. GLM, SAS v9.4). White grape pomace showed good suitability for ensiling, and stabilisation was achieved on day 35. The microbial populations and fermentative components observed in silage treatments adhered to the expected standards for high-quality ensiling processes. There were no significant losses of dry matter, and no significant differences were observed in the nutritional composition for ruminant feeding. A small reduction in antioxidant potential was observed and considered irrelevant in terms of the bioactive properties of the silages. Additionally, the cost analysis demonstrated that white grape pomace silage could serve as a more economical feedstuff compared to conventional forages, considering its nutritional value. So, the ensiling of white grape pomace in baled silage is a suitable and cost-effective technique that allows its preservation over a long period.