Effects of Sulla forage (Sulla coronarium L.) on the oxidative status and milk polyphenol content in goats

Twelve milking Girgentana goats were allocated into 3 groups and fed 3 diets ad libitum in a 3 × 3 Latin square design with 3 periods. The diets were Sulla fresh forage ad libitum (SUL), Sulla fresh forage ad libitum and 800 g/d of barley meal (SULB), and mixed hay ad libitum and 800 g/d of barley meal (HB). Changes were observed in total polyphenol intake, plasma oxidative status, plasma polyphenol content, metabolic status, milk polyphenol content, and total antioxidant capacity. The fresh forage diets (SUL and SULB) increased dry matter, total polyphenol, nontannic polyphenol and tannin intakes, and the milk total protein, casein, milk total polyphenols, and milk free polyphenols compared with the HB diet. The intake of condensed tannins was higher in the SUL than in the HB group, and an intermediate value was recorded for the SULB group. Plasma from the SUL- and SULB-fed goats exhibited greater total antioxidant capacity and greater total polyphenol and free polyphenol levels compared with the plasma from the HB group. Positive correlations between plasma total antioxidant capacity and condensed tannins intake (r = 0.43), plasma total polyphenol and total polyphenol intake (r = 0.61), and plasma free polyphenol and milk total polyphenols (r = 0.38) were observed. The correlation between milk free polyphenols and whey total antioxidant capacity (r = 0.42) highlights the role of free polyphenols in the determination of the antioxidant activity of milk. These results indicate that Sulla fresh forage exerts an antioxidant activity due to its secondary compounds that provide additional antioxidant value and that Sulla forage appears to be a promising strategy for improving product quality.