In vitro digestibility and gas production kinetic characteristics of corn stover treated by calcium oxide and stored under anaerobic condition

Abstract Text: As a large agricultural country, China is rich in corn stover resource. The nutritional value of corn stover can be improved by calcium oxide (CaO) treatment. Anaerobic storage is an effective method to prevent the treated stover from molding. A 1 plus 3 × 3 design was used to investigate the effect of CaO level and moisture content on the in vitro organic matter disappearance (IVOMD) and gas production in 72h (GP_72h). Ground stover was treated with different levels of CaO (3%, 5%, and 7%) and moisture content (40%, 50%, and 60%).  Untreated stover was used as control. Treated stover was kept under anaerobic condition for 15 days. Four Holstein cows with ruminal cannulas were used as animal donors of rumen fluid. An automated gas production system was used. Half gram of samples was added to each bottle (4 replicates/sample). Data were analyzed using single degree of freedom contrast to compare all the treatments with the control, and data excluding the control were further analyzed as a  3 × 3 factorial arrangement of treatments. There were no treatment interaction (P > 0.01) but differences  (P < 0.01) were found for main effects of moisture and CaO on IVOMD. The CaO level affected (P < 0.01) GP_72h, but the moisture content and its interaction with CaO level had no effect (P > 0.01) on GP_72h. The rate, halftime, and AGPR (gas production rate when gas production is 1/2 of the maxium) of gas production were not affected (P > 0.01) by the moisture or CaO level. As CaO level increased from 3% to 7%, IVOMD increased from 45.36% to 52.66%.The combination of CaO level and moisture content that resulted in the highest IVOMD was 7% CaO at 50% moisture content. There were no significant differences (P > 0.01) in IVOMD between stover treated with 5% CaO at 50% or 60% moisture content and that treated with 7% CaO at 50% moisture content. Under 50% and 60% moisture content, the level of CaO above 5% was not able to further improve the IVOMD. When treated with 5% CaO at 60% moisture content, the IVOMD and GP_72hof corn stover can be improved by 25.94% and 13.91%. Based on this study, the level of 5% CaO at 50% or 60% moisture content seems to be the best treatment combination. 

Keywords: corn stover; calcium oxide treatment; in vitro digestibility