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Altering the ruminal microbiota in dairy calves using rumen contents dosing.

M. Cox




Altering the ruminal microbiota in dairy calves using rumen contents dosing.
M. Cox*1, P. Weimer2,1, A. Steinberger1, J. Skarlupka1, G. Suen1. 1Department of Bacteriology, University of Wisconsin-Madison Madison, WI, 2US Dairy Forage Research Center, USDA Agricultural Research Service Madison, WI.

A major goal in dairy research is to improve milk production efficiency (MPE). With the advent of next-generation sequencing and its use in characterizing microbial communities, efforts are underway to improve MPE by manipulating the rumen microbiota. MPE is correlated with ruminal bacterial community composition (BCC), but the adult rumen microbiota is highly stable and returns to a baseline BCC even after heavy perturbation. We seek to influence rumen BCC by early intervention in pre-weaning dairy calves. Two cannulated Holstein donors of disparate MPE were selected. Three cohorts of 6 bull calves were established and dosed by gavage with a rumen inoculum sourced from the high-efficiency donor (HE), the low-efficiency donor (LE), or an autoclaved 50:50 mix as a microbe-free control (C). Dosing occurred within 3 d of birth, then every 2 weeks through 6 weeks of age. Feces were collected at each dosing as a proxy for gut BCC. Daily dry matter intake of calf starter, which has been shown to predict downstream feed efficiency, was greatest in HE calves and lowest in C calves (P < 0.05), though preweaning average daily gain did not differ between cohorts (P = 0.210). Calves were sacrificed at 8 weeks to access rumen contents and rumen wall sections were collected to assess papillation. Fecal and rumen samples were subjected to 16S rRNA amplicon sequencing. We found that BCC differed by cohort in fecal and rumen samples (P < 0.05), with HE calf samples most similar to adult rumen samples and C calves least similar. Additionally, HE calves tended to have elongated papillae (P = 0.062), the development of which is dependent on byproducts of microbial metabolism in the rumen and the long-term impact of which points to differences in absorptive capacity of the ruminal epithelium. These data demonstrate that the rumen BCC can be influenced by early intervention. Ongoing work includes expansion of this dosing protocol to a cohort of 60 female calves, following rumen BCC development and the impact on MPE in through the first lactation.

Keywords: rumen, calf, microbiota.

Biography: I am a 5th year Ph.D student in the Microbiology Doctoral Training Program at UW-Madison. I am broadly interested in host-associated microbial communities and their impact on host health. My undergraduate work at the University of Puget Sound in Tacoma, WA was on sexual asymmetry in cloacal communities of the striped plateau lizard. In graduate school I became interested in animal production systems and how principles of microbial community ecology might be leveraged to improve environmental, economic, and animal welfare outcomes. I love working in dairy and I hope to continue to do so after my graduation in Fall 2021.