Rumen fermentation, methane production, and microbial composition following in vitro evaluation of red ginseng byproduct as a protein source

The main objective of this in vitro study was to evaluate red ginseng byproduct (RGP) as a protein resource and its effects on rumen fermentation characteristics, microflora, CO 2 , and CH 4 production in ruminants. Four treatments for in vitro fermentation using buffered rumen fluid over a 48 h incubation period were used: 1, RGP; 2, corn gluten feed (CGF); 3, wheat gluten (WG); and 4, corn germ meal. In vitro dry matter digestibility (IVDMD), in vitro neutral detergent fiber digestibility (IVNDFD), in vitro crude protein digestibility (IVCPD), volatile fatty acids, pH, and ammonia nitrogen (NH 3 -N) were estimated after 48 h incubation. Gas production was investigated after 3, 6, 12, 24, 36 and 48 h. The CO 2 and CH 4 were evaluated after 12, 24, 36, and 48 h. A significant difference in total gas production and CO 2 emissions was observed (p < 0.01) at all incubation times. CH 4 production in RGP were higher (p < 0.05) than that in other treatments but a higher CH 4 portion in the total gas production was observed in WG (p < 0.05) at 48 h incubation. The IVDMD, IVNDFD, and IVCPD of RGP was lower than those of other conventional ingredients (p < 0.01). The RGP had the lowest NH 3 -N value among the treatments (p < 0.01). The RGP also had the lowest total VFA concentration (p < 0.01), but presented the highest acetate proportion and acetate to propionate ratio among the treatments (both, p < 0.01). The abundance of Prevotella ruminicola was higher in RGP than in WG (p < 0.01), whereas RGP has lower methanogenic archaea (p < 0.01). In conclusion, based on the nutritive value, IVDMD, low NH 3 -N, and decreased methanogenic archaea, RGP inclusion as a protein source in ruminant diets can be an option in replacing conventional feed sources.