Effects of leaf extracts of caragana on silage quality and antioxidant activity of alfalfa

The aim of this study was to investigate the effects of caragana leaf extract (LEC) on silage quality and the antioxidant activity of alfalfa (Medicago sativa). The supplemental LEC levels were 0 (control group, CON), 1% (LEC₁), 2% (LEC₂), and 3% (LEC₃) in fresh alfalfa. After 60 days, the nutritional quality, fermentation quality, and antioxidant activity indices of the alfalfa silage were determined. The results showed that: 1) the dry matter (DM) and lactic acid (LA) contents of the LEC₂ and LEC₃ groups were significantly higher than those of the CON group (P < 0.05), and the DM loss of the LEC₂ and LEC₃ groups was significantly lower than that of the CON group (P < 0.05). The water-soluble carbohydrate content of the LEC₃ group was significantly higher than that of the other groups (P < 0.05). LEC significantly decreased the pH value, propionic acid content, and yeast population of alfalfa silage (P < 0.05), and significantly increased the lactic acid bacteria population (P < 0.05). The LA contents of the LEC₂ and LEC₃ groups were significantly higher than those of the CON group (P < 0.05). 2) LEC significantly increased the flavonoid content, total antioxidant capacity, glutathione peroxidation activity, and superoxide dismutase activity of alfalfa silage (P < 0.05), and the total phenol and total polysaccharide contents of the LEC₃ group were significantly higher than those of the CON group (P < 0.05). The scavenging rates of 1,1-diphenyl-2-doctoral programs in public health (DPPH) free radicals in the LEC₂ and LEC₃ groups were significantly higher than those in the CON group (P < 0.05), and the DPPH radical scavenging rate was > 90% in all LEC addition groups. 3) The rankings of the principal component analysis and comprehensive score were LEC₃ > LEC₂ > LEC₁ > CON. In conclusion, the addition of LEC improved the nutritional and fermentation quality of alfalfa silage and enhanced the antioxidant activity of alfalfa silage. The 3% LEC treatment performed better than the other treatments.