Rumen bacterial communities can be acclimated faster to high concentrate diets than currently implemented feedlot programs

Abstract

Aims: Recent studies have demonstrated RAMP, a complete starter feed, to have beneficial effects for animal performance. However, how RAMP may elicit such responses is unknown. To understand if RAMP adaptation results in changes in the rumen bacterial community that can potentially affect animal performance, we investigated the dynamics of rumen bacterial community composition in corn-adapted and RAMP-adapted cattle.

Methods and results: During gradual acclimation of the rumen bacterial communities, we compared the bacterial community dynamics in corn and RAMP-adapted using 16S rRNA gene amplicon sequencing. Significant shifts in bacterial populations across diets were identified. The shift in corn-adapted animals occurred between adaptation step3 and step4, whereas in RAMP-adapted cattle, the shift occurred between step2 and step3. As the adaptation program progressed, the abundance of OTUs associated with family Prevotellaceae and S24-7 changed in corn-adapted animals. In RAMP-adapted animals, OTUs belonging to family Ruminococcaceae and Lachnospiraceae changed in abundance.

Conclusions: Rumen bacteria can be acclimated faster to high concentrate diets, such as RAMP, than traditional adaptation programs and the speed of bacterial community acclimation depends on substrate composition.

Significance and impact of the study: These findings may have implications for beef producers to reduce feedlot costs, as less time adapting animals would result in lower feed costs. However, animal feeding behavior patterns and other factors must be considered.

Keywords: 16S rRNA; RAMP; bacteria; microbial community; rumen microbiology.

Figure 1

Principle coordinate analysis and unweighted UniFrac distances relative to step1 diet. Principle coordinate analysis of unweighted UniFrac distances between four step‐up diets and the finisher diet during corn‐adaptation and RAMP‐adaptation programs (a). Unweighted UniFrac distances relative to step1 were used to identify shifts in bacterial community composition between subsequent steps (compared using Mann–Whitney U tests) in the adaptation programs. A single shift in the community composition was identified between step3 and step4 during corn‐based adaptation (b) while two earlier shifts, step1 to step2 and from step2 to step3, were detected during RAMP‐adaptation (c). C1–C4 represents adaptation steps during corn‐based adaptation; R1–R4 represents adaptation steps during RAMP‐based adaptation. CF and RF represent corn‐ and RAMP‐adapted animals on the same finisher diet, respectively. (), C1; (), C2; (), C3; (), C4; (), CF; (), R1; (), R2; (), R3; (), R4; (), RF.

Figure 2

Hierarchical clustering revealed two groupings of samples from corn‐adapted and RAMP‐adapted step‐up diets. One cluster contains samples prior to the shift in bacterial community composition during corn‐adaptation (step1, step2, and step3) along with step1 and step2 of RAMP‐adaptation. The second cluster contains ‘acclimated’ communities from step4 and finisher of corn‐adapted animals and step3, step4, and finisher of RAMP‐adapted animals. Only operational taxonomic units (OTUs) with a maximum relative abundance >1% are shown. Samples are labeled with their step‐up diets followed by an underscore and the animal identifier. C1–C4 represents adaptation steps during corn‐based adaptation; R1–R4 represents adaptation steps during RAMP‐based adaptation. CF and RF represent samples from the same finisher diet.

Figure 3

Heatmaps for operational taxonomic units (OTUs) identified as having a significantly different abundance prior to or after an identified bacterial community shift during corn‐based (a) and RAMP‐based adaptation (b, c) to high concentrate diets. OTUs are ordered by decreasing linear discriminant analysis score (as calculated by LEfSe). Only OTUs with a maximum relative abundance >1% are shown. Samples are labelled with their step‐up diets followed by an underscore and the animal identifier. C1–C4 represents adaptation steps during corn‐based adaptation; R1–R4 represents adaptation steps during RAMP‐based adaptation. CF and RF represent samples from the same finisher diet.

Figure 4

Venn diagrams displaying the distribution of operational taxonomic units (OTUs) among step‐up diets during corn‐adaptation (a) and RAMP‐adaptation (b) to high concentrate diets. C1–C4 represents adaptation steps during corn‐based adaptation; R1–R4 represents adaptation steps during RAMP‐based adaptation. CF and RF represent samples from the same finisher diet.