In vitro nutritional quality and antioxidant activity of three weed species as feed additives for sheep in the Central Highlands of Mexico

Sheep production is traditional for rural communities in Mexico, based on natural grasslands and semi-stabled feeding. Quality forages are necessary to improve productivity in these systems. Weeds are an alternative to feed ruminants and to manage crops. Also, many plants have secondary metabolites beneficial for livestock. The objective was to assess the nutritive value in vitro and the antioxidant activity of three weeds ( Tithonia tubiformis , Cosmos bipinnatus , and Tagetes lucida ) and four treatments (T0 = control diet, T1 = diet + 5% T. tubiformis , T2 = diet + 5% C. bipinnatus , and T3 = diet + 5% T. lucida ). Nutritive value was determined from chemical composition by standard methods and mineral contents by inductively coupled plasma analyses. Secondary compounds, total phenols (TP), total tannins (TT), condensed tannins (CT), and phenolic compounds, were determined by high-performance liquid chromatography, and total antioxidant activity was determined by measuring the oxygen radical absorbance capacity. Rumen fermentation kinetics and in vitro digestibility of dry matter (IVDMD), organic matter (IVOMD), and neutral detergent fibre (IVNDFD) were determined per species and treatment by in vitro gas production. T. tubiformis had the highest CP and TP contents ( P