Songklanakarin J. Sci. Technol. 40 (4), 896-903, Jul - Aug. 2018 Original Article Effects of ensiled Aspergillus oryzae and Saccharomyces cerevisiae cassava pulp as replacement for concentrate on ruminal fermentation in rumen-fistulated cows Wisitiporn Suksombat*, Jukkrit Homkaow, and Chayapol Meeprom School of Animal Production Technology, Institute of Agricultural Technology, Suranaree University of Technology, Mueang, Nakhon Ratchasima, 30000 Thailand Received: 11 June 2016; Revised: 1 May 2017; Accepted: 16 May 2017 Abstract Four experiments were conducted. I) The concentration of reducing sugar was determined following incubation with Aspergillus oryzae and an 8x11 factorial arrangement with 8 formulas of cassava components and 0 to 10 d of incubation. The reducing sugar increased from day 3 and the highest was found for 100% cassava pulp. II) Crude protein (CP) and urea content were determined after incubating with A. oryzae and Saccharomyces cerreviseae and a 4x6 factorial arrangement with 4 formulas of cassava components and 6 urea levels. The highest CP was observed in 37.5% cassava pulp, 25% cassava chip, and 37.5% cassava peel. III) The design was a 3x4 factorial arrangement with 3 formulas of cassava components and 4 urea levels. CP was unaffected by cassava components but increased with increasing urea levels. IV) The design was a 3x3 Latin squares with 3 fistulated cows and 3 periods. Treatments were 4 kg/cow/d concentrate, 3.2 kg/cow/d concentrate plus 0.8 kg/cow/d ensiled cassava pulp (ECP) and 2.4 kg/cow/d concentrate plus 1.6 kg/cow/d ECP. ECP increased pH, molar proportions of acetic and butyric acids but reduced molar proportion of propionic acid. Keywords: Aspergillus oryzae, Saccharomyces cerevisiae, ensiled cassava products, cassava pulp, cassava peel 1. Introduction In the processing of cassava flour and after re- moving the flour from the tuber, the rest is cassava pulp which can be used as animal feed. Unfortunately, the protein content of the peel and pulp is low and cannot be regarded as good quality feed for animals. However, it has been reported that fermentation of carbohydrate substrates by micro-organisms could bring about an increase in crude protein (CP) content (Antai & Mbongo, 1994). Fungal and yeast fermentations have been identified as inexpensive tools to increase the pro- tein level of such by-products. The attractive characteristics in the use of microorganisms include their fast growth rate, the high level of protein, and the comparable good nutritional values. Fungal cellulase and amylase, particularly from Aspergillus species is widely used for commercial enzyme production. Recently, Aspergillus oryzae has been reported to yield cellulase activity (Begum et al., 2009), which is an important enzyme required for the catabolism of cellulose into smaller sugars. In addition, A. oryzae also has an excellent capacity of α-amylase production under solid state fermenta- tion using spent brewing grains (Francis et al., 2002) and wheat bran (Sivaramakrishnan et al., 2007). Therefore, the highest reducing sugar content of cassava pulp fermentation with A. oryzae may indicate the capability of A. oryzae to pro- duce enzymes, especially cellulase and amylase to hydrolyze glucosidic linkages in polysaccharides. Utilization of local feed especially fermentation of cassava peels by pure culture Saccharomyces cerevisiae could increase its protein content from 2.4% in non-fermented cassava to 14.1% in fermented products (Antai & Mbongo, 1994). Fermentation of cassava flour with S. cerevisiae en- hanced the protein level from 4.4% to 10.9% and decreased *Corresponding author Email address: wisitpor@sut.ac.th