This study was conducted to investigate the effect of biological treatments to improvement on the in vitro digestibility disappearance for rice straw.  The parameter used in this study includes; gas-production, IVDMD, IVMOD and pH value. The experiment was divided into seven treatments:

1^st treatment: considered as control group was used 3g from straw only.
2^nd treatment: Fibrolytic enzymes group 0.3g with 3g from straw.
3^rd treatment: Fibrolytic enzymes group 0.4g with 3g from straw.
4^th treatment: Saccharomyces cerevisie group 0.3g with 3g from straw.  
5^th treatment: Saccharomyces cerevisie group 0.4g with 3g from straw.
6^thtreatment: The mix group between fibrolytic enzymes group 0.3g and Saccharomyces cerevisie group 0.3g with 3g from straw.
7^thtreatment: The mix group between fibrolytic enzymes group 0.4g and Saccharomyces cerevisie group 0.4g with 3g from straw.

 
The results showed a significant increase (P<0.05) of 6th group in gas production as compared with 3^rd group at the beginning of the experiment. Also the 3^rd group showed a significant increase (P<0.05) in gas production as compared
with 5^th group after 10 hrs. from the period of incubation. It has been observed that there was a significant increase (P <0.05) in the 3^rd group in gas produced as compared with 4^th  and 5^th  group after 12 hrs from the period of incubation. The result also showed a significant effect (P <0.05) in the 2^nd and 6^th groups in the gas production as compared with 5th group after 24 hrs the period of incubation. It has been observed after 48 hrs the period of incubation, there was a significant effect (P<0.05) in gas produced in all treated groups as compared with 5^th group. It has been noticed from the experiment that there was result a significant increase (P<0.05) in 5^th, 6^th groups of pH value as compared with 2^nd and 4^th groups. The results showed a significant effect (P<0.05) in the 3^rd group in IVDMD as compared with 6^th group, Similarly, there showed a significant effect (P<0.05) in the 1st, 3^rd, 5^th, 6^th, 7^th groups in the IVDMD as compared with 4^th group. There was also a significant effect (P<0.05) in the 3^rd in IVMOD value than that with 6^th group. It has been shown that there was a significant effect (P <0.05) in the 6^th group of IVMOD value as compared with 2^nd, 4^th and 7^th groups. Finally it has observed that there was a significant effect (P <0.05) in the control group (1^st), 5^th and 7^th groups in IVMOD value as compared with 4^th group.
It was concluded from this study that addition of fibrolytic enzymes and a combination of fibrolytic enzymes and saccharomyces cerevisie could improve digestibility of rice straw in vitro.