Effect of Brittleness in Rice Straw on Rumen Fermentation by In vitro Gas Production Technique

The objective of this study was to examine the impact of rice straw brittleness on its efficacy as roughage for ruminants, in comparison to a wild-type variety, utilizing an in vitro study approach. The experimental design was a complete randomized design (CRD). The experimental treatments included various breeds of rice straw (RS), such as the wild-type (WT, T1), the green brittle bred line 8 and line 13 with brittleness level-3 (GBL8-B3, T2 and GBL13-B3, T3), and the purple brittle bred line 8 with brittleness level-5 (PBL8-B5, T4). The findings revealed that the brittleness RS group had higher levels of crude protein and hemicellulose, and lower levels of cellulose compared to the wild-type group. Brittleness RS varieties showed a significantly greater gas production accumulation (p = 0.001) and IVDMD (p = 0.003) compared to the WT group. At 8 h post-incubation, the brittleness RS group showed significantly higher (p = 0.004) total of volatile fatty acids concentration compared to the WT group. After 1 h of post-incubation, GBL8-B3 exhibited the highest (p = 0.032) proportion of propionate and the lowest (0.009) C2:C3 ratio. Additionally, the brittleness RS did not have any effect on the population of ruminal microorganisms. Based on the brittleness of RS, it can be deduced that it has a greater potential as a roughage source when compared to the wild-type variety, consequently enhancing the quality of RS for roughage intake by ruminants. HIGHLIGHTS Brittleness RS exhibited elevated levels of CP, high hemicellulose content, and lower cellulose levels compared to the WT group. The brittleness RS group displayed a rapid degradation rate impacting the total VFAs concentration and C2:C3 ratio, with the GBL8-B3 group demonstrating superior utilization efficiency. The brittleness of RS is indicative of a higher potential as a roughage source when compared to the wild-type variety, thereby improving the quality of rice straw for roughage consumption by ruminants. GRAPHICAL ABSTRACT