Effect of feeding fresh or dehydrated sulla forage on microbiological, nutritional, and sensory traits of sheep cheese

ABSTRACT: Sulla is a forage legume species exploited mainly by grazing ruminants, greatly appreciated for its high protein content and moderate levels of condensed tannins with antioxidant activity. This study was aimed to explore the potential of sulla in relation to its seasonal utilization, as fresh or stored forage, and to improve the quality traits of sulla forage stocks, proposing dehydration as alternative to haymaking. Two experiments were carried out in different seasons, spring and autumn, both involving Valle del Belìce ewes fed different diets evaluated in terms of dairy production. In the spring experiment, diets consisting of fresh sulla forage (SUL) or fresh barley forage (BAR) provided ad libitum were compared using 12 ewes at 70 DIM divided into 2 groups and fed the 2 diets in a 2 × 2 Latin square design. In the autumn experiment, pellets of dehydrated sulla forage (DSF) obtained from an early (April) or a late (May) cutting time were compared with sulla hay (SH) using 9 ewes at 60 DIM divided into 3 groups and fed the following 3 diets in a 3 × 3 Latin square design: 2 kg/d per ewe of April pellets and SH ad libitum (A-DSF); 2 kg/d of May pellets and SH ad libitum (M-DSF); and SH ad libitum (SHL). Concentrate feed was supplied to all ewes (600 or 800 g/d in spring and autumn, respectively). In both experiments, cheeses manufactured from bulk milk of the different groups were sampled at 15 and 30 d of storage. In spring, compared with BAR, SUL improved the milk casein content, and in cheeses increased the level of PUFA, especially rumenic and α-linolenic acids, reduced redness index (a*) and fat content. In autumn cheese, DSF diets enhanced total PUFA, especially due to linoleic and α-linolenic acids, and polyphenol contents, whereas the A-DSF diet tended to improve the cheese antioxidant capacity, regardless of storage time. The microbiological profile of spring and autumn cheeses was almost similar among diets, indicating no negative effect of stored forages on fermentation process. In triangle tests, the panel was able to distinguish cheese from different diets for both seasons and storage times, without recording differences in their acceptance degree. These results highlight the advantages of dehydration as an alternative to haymaking, and confirm the promising potential of DSF in ensuring adequate dairy production during periods of limited fresh forage availability.