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

Abstract

The main objective of this <i>in vitro</i> study was to evaluate red ginseng byproduct (RGP) as a protein resource and its effects on rumen fermentation characteristics, microflora, CO₂, and CH₄ production in ruminants. Four treatments for <i>in vitro</i> 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. <i>In vitro</i> dry matter digestibility (IVDMD), <i>in vitro</i> neutral detergent fiber digestibility (IVNDFD), <i>in vitro</i> crude protein digestibility (IVCPD), volatile fatty acids, pH, and ammonia nitrogen (NH₃-N) were estimated after 48 h incubation. Gas production was investigated after 3, 6, 12, 24, 36 and 48 h. The CO₂ and CH₄ were evaluated after 12, 24, 36, and 48 h. A significant difference in total gas production and CO₂ emissions was observed (<i>p</i> < 0.01) at all incubation times. CH₄ production in RGP were higher (<i>p</i> < 0.05) than that in other treatments but a higher CH₄ portion in the total gas production was observed in WG (<i>p</i> < 0.05) at 48 h incubation. The IVDMD, IVNDFD, and IVCPD of RGP was lower than those of other conventional ingredients (<i>p</i> < 0.01). The RGP had the lowest NH₃-N value among the treatments (<i>p</i> < 0.01). The RGP also had the lowest total VFA concentration (<i>p</i> < 0.01), but presented the highest acetate proportion and acetate to propionate ratio among the treatments (both, <i>p</i> < 0.01). The abundance of <i>Prevotella ruminicola</i> was higher in RGP than in WG (<i>p</i> < 0.01), whereas RGP has lower methanogenic archaea (<i>p</i> < 0.01). In conclusion, based on the nutritive value, IVDMD, low NH₃-N, and decreased methanogenic archaea, RGP inclusion as a protein source in ruminant diets can be an option in replacing conventional feed sources.