Dehydrated Sulla forage in dairy ewes feeding: effects on cheese properties

Feeding green sulla forage (GSF) (Sulla Coronarium L.), a shortlived perennial legume containing phenolic compounds, especially condensed tannins, showed to increase intake, milk yield and casein level in ruminants, and enhance fatty acid (FA) profile and antioxidant activity of dairy products. To obtain analogous favourable effects using conserved sulla forage, dehydration could be a valid alternative to the haymaking process which causes greater losses of biomass and its nutritional and bioactive compounds. The aim of this research was to evaluate the dairy products from ewes fed with pelleted dehydrated sulla forage (PDSF) in the diet by comparisons with those obtained using sulla hay (SH) and GSF based diets. Twenty primiparous (PR) and pluriparous (PL) milking Valle del Belice ewes were allocated homogeneously into 5 groups and fed 5 diets in a partial 5 × 2 Latin square design with 2 periods. The diets differed for the forage component: SH ad libitum (SHL); 2 kg/d per ewe of PDSF and SH ad libitum (DSF); 2 kg/d of GSF and SH ad libitum (2GSF); 4 kg/d of GSF and SH ad libitum (4GSF); GSF ad libitum (GSFL). Concentrate feed was supplied to PR (0.8 kg/d) and PL (1.2 kg/d) ewes in the function of their different production needs. The results confirmed the superiority of diet in which GSF was the only forage source offered ad libitum, as occurs with grazing; in fact, the GSFL diet resulted in higher milk yield and casein content and enhanced in cheese the number of polyphenols and antioxidant vitamins A and E, the oxidative stability, and the level of health polyunsaturated FA (PUFA) such as rumenic, the main of conjugated linoleic acids (C18:2c9t11), and α-linolenic (ALA, C18:3n-3). On the whole, the DSF diet showed better results than SHL and was comparable to the 4GSF diet for milk yield and casein level and, in cheese, for external colour and vitamin A and total PUFA contents; moreover, ALA was detected at the same high level in DSF and GSFL cheeses. Thus, dehydration seems to represent a valid opportunity to exploit the considerable potential of sulla forage, and maintain adequate production levels and nutritional and health properties of milk and cheese in periods of insufficient grazed green resources.