Pretreatment of crop residues by ammonia fiber expansion (AFEX) alters the temporal colonization of feed in the rumen by rumen microbes

Citation

Terry, S.A., Ribeiro, G.O., Conrad, C.C., Beauchemin, K.A., McAllister, T.A., Gruninger, R.J. (2020). Pretreatment of crop residues by ammonia fiber expansion (AFEX) alters the temporal colonization of feed in the rumen by rumen microbes. FEMS Microbiology Ecology, [online] 96(6), http://dx.doi.org/10.1093/femsec/fiaa074

Plain language summary

This study examines the colonization of barley straw (BS) and corn stover (CS) by rumen bacteria and how this is impacted by pretreatment technologies that aim to enhance the digestibility of crop by-products. Ruminally cannulated beef heifers were used to investigate in situ microbial colonization of feed in the rumen. Crop residues were incubated in the rumen for 0, 2, 4, 8 and 48 h and the colonizing microbial community was examined using 16 s rRNA gene sequencing. The surface colonizing community clustered based on incubation time and pre-treatment indicating that pre-treatment of feed does have an effect on feed colonization. Fibrobacter, unclassified Bacteroidales, and unclassified Ruminococcaceae were enriched during late stages of colonization while Prevotella and unclassified Lachnospiraceae were enriched in the early stages of colonization. The microbial community colonizing BS-AFEX and CS was less diverse than the community colonizing BS and CS-AFEX. Prevotella, Coprococcus and Clostridium were enriched in both AFEX crop residues, while untreated crop residues were enriched with Methanobrevibacter. Several pathways associated with simple carbohydrate metabolism were enriched in the primary colonizing community of AFEX crop residues. This study suggests that AFEX improves the degradability of crop residues by increasing the accessibility of polysaccharides that can be metabolized by the dominant taxa responsible for primary colonization.

Abstract

This study examines the colonization of barley straw (BS) and corn stover (CS) by rumen bacteria and how this is impacted by ammonia fiber expansion (AFEX) pre-treatment. A total of four ruminally cannulated beef heifers were used to investigate in situ microbial colonization in a factorial design with two crop residues, pre-treated with or without AFEX. Crop residues were incubated in the rumen for 0, 2, 4, 8 and 48 h and the colonizing profile was determined using 16 s rRNA gene sequencing. The surface colonizing community clustered based on incubation time and pre-treatment. Fibrobacter, unclassified Bacteroidales, and unclassified Ruminococcaceae were enriched during late stages of colonization. Prevotella and unclassified Lachnospiraceae were enriched in the early stages of colonization. The microbial community colonizing BS-AFEX and CS was less diverse than the community colonizing BS and CS-AFEX. Prevotella, Coprococcus and Clostridium were enriched in both AFEX crop residues, while untreated crop residues were enriched with Methanobrevibacter. Several pathways associated with simple carbohydrate metabolism were enriched in the primary colonizing community of AFEX crop residues. This study suggests that AFEX improves the degradability of crop residues by increasing the accessibility of polysaccharides that can be metabolized by the dominant taxa responsible for primary colonization.