Seasonal Variations of the Nutritive Value and Phytotherapeutic Potential of Cladium mariscus L. (Pohl.) Targeting Ruminant’s Production

In our endeavor to identify salt-tolerant plants with potential veterinary uses in ruminants’ production strategies, we focused on Cladium mariscus L. Pohl (sawgrass), due to its high total phenolic and tannin content, anti-radical properties, and ethnomedicinal uses. Aerial parts were collected along the year in Southern Portugal and evaluated for the nutritional profile and in vitro organic matter digestibility (IVOMD), aiming for its use as feed. Acetone extracts were appraised for total contents in phenolics (TPC), flavonoids (TFC), and tannins (CTC), as well as the chemical composition by HPLC-DAD and in vitro antioxidant and anti-inflammatory properties, targeting its exploitation as phytotherapeutic products. Sawgrass biomass has a limited nutritive value, due to its high neutral detergent fiber (NDF; 596–690 g kg(−1) dry matter (DM)) and acid detergent fiber (ADF; 330–418 g kg(−1) DM) contents, low crude protein (51.8–87.3 g kg(−1) DM) and IVOMD (172–317 g kg(−1) organic matter (OM)). Despite differences among seasons, the mineral profile was adequate. The extracts were rich in TPC (88–112 mg g(−1)), CTC (115–169 mg g(−1)), and TFC (18.5–20.2 mg g(−1)), and displayed significant antioxidant capacity, particularly in summer and autumn, whilst no seasonal influence was detected for anti-inflammatory properties (30% reduction of nitric oxide production). Eleven phenolics were quantified: chlorogenic, ferulic, and syringic acids were the most abundant, especially in the autumn sample. Overall, despite the low nutritional interest, sawgrass extracts hold the potential as a source of antioxidant and anti-inflammatory phenolic compounds.