Effects of a moderate or aggressive implant strategy on the rumen microbiome and metabolome in steers

Authors: HENNIGER, MADISON - University Of Tennessee; Wells, James - Jim; Hales Paxton, Kristin; Lindholm-Perry, Amanda; Freetly, Harvey; Kuehn, Larry; SCHNEIDER, LIESEL - University Of Tennessee; MCLEAN, KYLE - University Of Tennessee; CAMPAGNA, SHAWN - University Of Tennessee; CHRISTOPHER, COURTNEY - University Of Tennessee; MYER, PHILLIP - University Of Tennessee

Submitted to: Frontiers in Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2022
Publication Date: 5/31/2022
Citation: Henniger, M.T., Wells, J.E., Hales, K.E., Lindholm-Perry, A.K., Freetly, H.C., Kuehn, L.A., Schneider, L.G., McLean, K.J., Campagna, S.R., Christopher, C.J., Myer, P.R. 2022. Effects of a moderate or aggressive implant strategy on the rumen microbiome and metabolome in steers. Frontiers in Animal Science. 3. Article 889817. https://doi.org/10.3389/fanim.2022.889817.
DOI: https://doi.org/10.3389/fanim.2022.889817

Interpretive Summary: Bacteria are present throughout nature and can have significant impact on biological processes. In animals, the intestinal tract harbors thousands of different bacteria and these microbes can impact health and wellbeing. Growth-promoting hormone implants can have significant impact on animal performance and although hormones have been shown to impact the host microbiota, the potential impact of these growth-promoting implants on the microbial populations has never been reported. The current study analyzed the microbial populations in samples collected from the rumen of feedlot cattle that had been treated with moderate or aggressive growth-promoting hormone implant strategies. Implant strategy had very little impact on the rumen microbial populations or the end-products of microbial fermentations. The research indicates that improvement in animal growth performance from aggressive growth-promoting implant strategies are not resulting from changes in the bovine rumen microbial populations.

Technical Abstract: The effects of growth-promoting implants have been well-defined for their ability to impact growth performance in beef cattle. Production-relevant microbes and microbiomes in the rumen have also been associated with growth traits. However, the role of implants on the rumen microbiome has not been determined. The objective of this study was to determine if different doses of implant hormones cause gain-associated ruminal microbial community changes. To assess this, a completely randomized design was used and 336 fall-born steers 450 to 470 days of age from the germplasm evaluation population at the US Meat Animal Research Center (Clay Center, NE) were divided into two treatment groups: 1) a moderate implant strategy (n = 167) of Revalor-IS (80 mg trenbolone acetate and 16 mg estradiol) followed by Revalor-S (120 mg trenbolone acetate and 24 mg estradiol) or 2) an aggressive implant strategy (n = 169) of Revalor-IS followed by Revalor-200 (200 mg trenbolone acetate and 20 mg estradiol). Steers were fed the same diet (57.0% dry-rolled corn, 30% wet distiller’s grains with solubles, 8.0% alfalfa hay, 4.25% vitamin and mineral supplement, and 0.75% urea, on a DM basis). On d 85 after implants administration, rumen contents were collected via orogastric tubing. Samples were sequenced to target and identify bacteria, archaea, and protozoa. Untargeted metabolomics was performed on rumen content using ultra high performance liquid chromatography high resolution mass spectrometry. Production data between implant strategies was analyzed using a mixed model ANOVA (SASv9.4, Cary, NC) followed by separation of least squares means. Microbial diversity between strategies did not differ for archaea or protozoa (P > 0.05). Average daily gain was different (P = 0.01; 1.72 vs 1.66 ± 0.02 kg, aggressive vs moderate, respectively); however, large microbial community shifts were not associated with implant strategy. Two metabolites, N-acetyllysine and N-acetylornithine, were found in greater abundance in the moderate implant strategy (P = 0.04). Understanding associations between the rumen microbiome and implant strategies may allow improvement of growth efficiency in beef cattle.