Feeding ruminants with agro-industrial by-products can help to fill feed shortages in dry period. The objectives of current study were to determine the nutritive value of several sun dried grapevine (raisin) by-products (RBPs) for ruminants using chemical composition analysis and in situ ruminal degradability. Several RBPs of sun dried treated grapevine cluster (Vitis vinifera L. cv. Sultana) include 1) outer layer of flesh and skin and pedicle of berries (RBP1); 2) rejected raisins mostly un-ripped berries with their pedicles (RBP2) and 3) peduncles and rachises with their lateral branches of clusters (RBP3). Results showed that the RBP1 had lower neutral detergent fiber, lignin (sa.) and nitrogen to organic matter ratio while these components were higher for RBP3, with RBP2 intermediate (P<0.05). The RBP1 and RBP3 had higher total tannin concentration compared with RBP2 (75.8 and 69.2 respectively versus 34.6 g/kg DM; P<0.05). The RBP1 had higher in situ ruminal degradation and lower undegradable fraction (predicted by in situ and DVE/OEB 1994 model) for dry matter (DM) and organic matter (OM) compared with RBP3, with RBP2 intermediate (P<0.01). In conclusion, the RBPs could be considered as alternative feed in ruminants feeding during dry periods; however, their tannin and lignin (sa) content should be taken into consideration for decision making.
