KECERNAAN JERAMI PADI SECARA IN VITRO YANG DIFERMENTASI DENGAN ARAS RAGI ISI RUMEN DAN WAKTU YANG BERBEDA [The In Vitro Digestibility of Rice Straw Fermented by Different Level of Fortified Rumen and Fermentation Times] - Sitorus, T.F (Faculty of Animal Agriculture, Diponegoro University, 2007)