Polyphenol Characterization and Antioxidant Capacity of Multi-Species Swards Grown in Ireland—Environmental Sustainability and Nutraceutical Potential

Ruminant production systems are major contributors to greenhouse gases emissions, with animal feeding practices being the main cause for methane and nitrous oxide’s release. Although feeding animals forages has been proven to be more sustainable, traditional ryegrass monocultures still require a lot of input (e.g., fertilisers and pesticides). Multi-species swards, consisting of different swards, such as grasses, forage legumes and herbs, need less management and fertiliser, produce more dry matter, and also add a variety of phytochemicals into the animal diet. In particular, polyphenols have been associated with a positive impact on animal health and productivity. However, data on the phenolic composition of multi-species sward components is still scarce, and little is known about the change in concentration over the grazing season. The present study investigated the antioxidant activity of six forage species (perennial ryegrass, timothy, white clover, red clover, chicory and plantain) over the Irish grazing season, using FRAP, DPPH•• and ORAC assays. The forages were screened for individual phenolic compounds using Liquid-Chromatography-Triple-Quadruple-Mass-Spectrometry. Plantain exhibited the highest antioxidant capacity, being almost one and a half times higher than timothy and double that of chicory. Chlorogenic acid was the most abundant polyphenol in perennial ryegrass, timothy and plantain. Overall, formononetin and biochanin A levels were higher in red clover, white clover and in chicory, in comparison to other forages (p < 0.05). Variations in antioxidant capacity and polyphenol composition were more significant between species (p < 0.01) than between season within species (p > 0.05). This study suggests that multi-species swards, regardless of the grazing month, offer a potential sustainable alternative to monoculture swards with significant antioxidant activity and nutraceutical compounds.