Pre-weaning ruminal administration of differentially-enriched, rumen-derived inocula shaped rumen bacterial communities and co-occurrence networks of post-weaned dairy calves

Authors: PARK, TANSOL - Oak Ridge Institute For Science And Education (ORISE); CERSOSIMO, LAURA - Orise Fellow; Li, Wenli; Radloff, Wendy; Zanton, Geoffrey

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2021
Publication Date: 2/26/2021
Citation: Park, T., Cersosimo, L.M., Li, W., Radloff, W.J., Zanton, G.I. 2021. Pre-weaning ruminal administration of differentially-enriched, rumen-derived inocula shaped rumen bacterial communities and co-occurrence networks of post-weaned dairy calves. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2021.625488.
DOI: https://doi.org/10.3389/fmicb.2021.625488

Interpretive Summary: Dairy cattle require a diverse ruminal microbial community to utilize human inedible feeds as substrates to produce milk. While the establishment of a microbial community can occur without the intervention of farm management, it might be possible to improve the ruminal microbial community through early-life inoculation. In this study, we evaluated the sustained effects of early-life inoculation with different microbial profiles on week 9 (post-weaning) performance and ruminal characteristics. We found that calves inoculated during week 3-6 with either bacteria-enriched or protozoa-enriched microbial inocula resulted in increased species richness (number of species) and species diversity at week 9. The proportion of those bacterial taxa possibly transferred from the rumen inoculum donor was minor. All calves inoculated with the protozoa-enriched inoculum had ruminal protozoa present at week 9, whereas calves that were not inoculated with protozoa did not have protozoa present at week 9. Receiving protozoa with the ruminal inoculum also resulted in higher concentrations of total volatile fatty acids which could result in greater absorption of these energy precursors to the post-weaned dairy calf although animal performance was unchanged. These results indicate that modest changes in the microbial community of inoculated calves were possible, but linking these responses to host characteristics will require further experimentation.

Technical Abstract: Adult rumen fluid inoculations have been considered to facilitate the establishment of rumen microbiota of pre-weaned dairy calves. However, the sustained effects of the inoculations remain to be explored. In our previous study, 20 pre-weaned dairy calves had been dosed with four types of adult rumen inoculums [autoclaved rumen fluid, bacterial-enriched rumen fluid (BE), protozoal-enriched (PE), and BE+PE] weekly at 3 to 6 weeks of age. To verify the sustainable effect of adult rumen inoculation, rumen bacterial community, fermentation characteristics, and animal performance measurements were analyzed after sacrifice from twenty post-weaned dairy bull calves (9 weeks of age) in this study. Ruminal pH tended to be lower in BE treated calves (n = 10). All PE treated calves had rumen ciliates (>104 cells per ml of rumen fluid). PE treated calves had greater VFA concentrations (P = 0.052), lower molar proportions of isobutyrate (P = 0.073), and butyrate (P = 0.019) compared to those of control calves. No treatment differences were found in all animal performance measurements. Both PE and BE inocula increased bacterial species richness, Faith’s phylogenetic diversity, and Shannon’s index in rumen liquid fractions. However, the relative proportion of those bacterial taxa possibly transferred from the donor’s rumen was minor. Microbial network analysis showed different co-occurrence and mutually exclusive interactions between treatments of microbial inoculations. Collectively, adult rumen inoculations in pre-weaned dairy calves slightly altered rumen bacteriome of post-weaned calves without changing fermentation and animal performance.