In vitro fermentation characteristics, microbial changes and gas production of microencapsulated phytonutrient pellets at varying dietary crude protein levels

The objective of this study was to investigate the influence of crude protein (CP) levels combined with the supplementation of a microencapsulated phytonutrients pellet made from a mixture of lemongrass and dragon fruit peel (MiEn-LEDRAGON) on gas production, degradability, fermentation characteristics, and microbial diversity using the in vitro gas technique. A 4 × 2 factorial arrangement in a completely randomized design (CRD) was used in this study, with four levels of CP in the concentrate diet (10, 12, 14, and 16% dry matter; DM) combined with two levels of MiEn-LEDRAGON supplementation (0 and 3% in the total DM substrate). The results of this study demonstrated that there were no interaction effects between CP levels and MiEn-LEDRAGON supplementation on gas production, degradability, fermentation characteristics, end-product formation, or microbial dynamics (p > 0.05). Additionally, increasing CP levels in the concentrate diet had no effect on cumulative gas production, gas kinetics, in vitro degradability, volatile fatty acids (VFA), or methane (CH₄) production (p > 0.05), but it did enhance in vitro pH and ammonia-nitrogen (NH₃-N), as well as increase the number of Fibrobacter succinogenes at 24 h (h) of incubation time (p < 0.05). Meanwhile, the study revealed higher cumulative gas production, degradability, NH₃-N, pH values, total VFA at 24 h of incubation, proportions of propionate (C3) at 12 and 24 h of incubation, and butyrate (C4) at 12 h of incubation, as well as increased numbers of F. succinogenes, Butyrivibrio fibrisolvens, and Butyrivibrio proteoclasticus at 12 h of incubation when supplemented with 3% MiEn-LEDRAGON in the total DM substrate (p < 0.05). It also decreased the proportion of acetate (C2), CH₄ production, and the populations of methanogens (Methanobacteriales) and Ruminococcus species (Ruminococcus albus and Ruminococcus flavefaciens) (p < 0.05). In summary, this study found that increasing CP levels in the concentrate diet did not negatively affect gas production, fermentation characteristics, end-product formation, or microbial dynamics. Moreover, MiEn-LEDRAGON supplementation could serve as an effective rumen-enhancing feed additive rich in phytonutrients for ruminants while also mitigating ruminal CH₄ production.