Hydroponic Forage in Ruminant Nutrition: A Systematic Review of Nutritional Value, Performance Outcomes, and Sustainability

This systematic review evaluated 28 peer-reviewed studies on the use of hydroponic forage in ruminant diets, following PRISMA 2020 guidelines. Hydroponic barley sprouts contain on average 14.8 ± 2.1% CP, 3.6 ± 0.4% EE, 12.9 ± 1.7% NDF, 7.8 ± 1.2% ADF, and 10.5 ± 2.8% DM (mean ± SD; n = 21 studies), and mineral content, though limited by high moisture and low dry matter yield. Among the included studies, 61% focused on barley, confirming its suitability for hydroponic cultivation. In dairy cattle, hydroponic forage improved milk fat content and oleic acid (C18:1), linoleic acid (C18:2), and α-linolenic acid (C18:3) and reduced saturated fatty acids without compromising yield. In buffaloes, inclusion enhanced cheese quality and reduced energy footprint, though costs were higher. For small ruminants and growing animals, moderate inclusion (5-25% dry matter) improved intake, digestibility, and growth, while excessive replacement reduced feed intake or digestibility, likely due to rumen microbiota shifts. Additionally, hydroponic feeding reduced methane emissions in lambs, highlighting its environmental potential. Overall, hydroponic forage can serve as a sustainable complement to conventional feed resources, promoting resource efficiency and animal performance when properly integrated into balanced diets. Further studies should define optimal inclusion rates and evaluate economic and environmental trade-offs under different production systems.