Dehydration preserves the ability of tanniferous sulla forage (Sulla coronaria (L.) Medik.) to improve nutritional, microbial and sensory traits of sheep cheese

Abstract

Sulla is a forage legume species appreciated for the positive impact on small ruminants’ dairy production, due to its high protein content and moderate level of phenolic compounds, consisting mainly of condensed tannins (CT). Fresh sulla forage (FSF) is exploited by grazing ewes during early spring, and then ungrazed to constitute hay stocks. Dehydration showed to be a valid alternative to haymaking for reducing the losses of biomass and nutrients and preserving the properties of bioactive components. This investigation was aimed to evaluate the potential of sulla in relation to its seasonal utilization, as fresh or stored forage. Two experiments were carried out, in spring (SPR) and autumn (AUT), both involving Valle del Belice ewes at 60 days in milk. In SPR, diets consisting of FSF or fresh barley forage (FBF) provided ad libitum were compared using 12 ewes divided into 2 groups and fed the 2 diets in a 2 × 2 Latin square design (LQD). In AUT, pellets of dehydrated sulla forage (DSF) obtained in 2 cutting times and differing in crude protein (CP) (April, 15.1% dry matter (DM); May, 11.3% DM) were compared with sulla hay (SH, CP 11.8% DM) using 9 ewes divided into 3 groups and fed the following 3 diets in a 3 × 3 LQD: ADSF, 2 kg/d per ewe of April pellets and SH ad libitum; MDSF, 2 kg/d of May pellets and SH ad libitum; SHL, SH ad libitum. Concentrate feed was supplied to all ewes (600 or 800 g/d in SPR and AUT). Manufactured cheeses were sampled at 15 and 30 d of storage. Compared to FBF, FSF improved milk yield (1460 vs 1774 g/d; p < 0.001), milk casein and milk conversion ratio (DM feed intake/milk yield), while in cheese increased the polyunsaturated fatty acids (PUFA), and reduced redness index (a*) and fat. In AUT, both ADSF and MDSF induced higher milk yield than SH (1661, 1538, 1374 g/d; p < 0.001), and in cheeses enhanced total PUFA, especially due to linoleic, α-linolenic and rumenic acids, while ADSF improved the cheese antioxidant capacity, regardless storage time. The microbiological profile of milk and cheese was similar among all diets, indicating no negative effect of stored forages on fermentation process. At triangle tests, the panel was able to distinguish cheeses from different diets for both seasons and storage times, without recording differences in their acceptance degree. The results confirmed the potential of DSF in ensuring adequate dairy productions in periods of unavailable fresh forage, especially when derives from early-cut forage.