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The effects of supplementing a seaweed, Asparagopsis taxiformis, to dairy cows on bacteria-archaea interactions in the rumen.

N. Indugu



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The effects of supplementing a seaweed, Asparagopsis taxiformis, to dairy cows on bacteria-archaea interactions in the rumen.
D. Pitta1, H. Stefenoni2, N. Indugu*1, M. Hennessy1, B. Vecchiarelli1, R. Shah3, S. Garapati4, C. Yarish5, S. Welchez2, S. R�is�nen2, D. Wasson2, C. Lage2, A. Melgar2, M. Fetter2, A. Hristov2. 1University of Pennsylvania School of Veterinary Medicine Kennett Square, PA, 2The Pennsylvania State University University Park, PA, 3University of Pennsylvania Philadelphia, PA, 4Drexel University Philadelphia, PA, 5University of Connecticut Stamford, CT.

Research has shown that feeding marine algae, such as Asparagopsis taxiformis (AT), severely inhibits methanogenesis in the rumen; however, the impact of feeding AT on rumen microbes is unknown. To determine the effect of feeding AT in dairy cows, 20 Holstein cows were randomly assigned to 4 [control (CON), 0.25% AT (LAT), 0.5% AT (HAT), and oregano leaves (ORE)] treatments in a replicated 4 � 4 Latin square design with four 28-d experimental periods. Toward the end of each period, ruminal samples were collected using a stomach tube and filtered through 3 layers of cheesecloth to separate the solid and liquid fractions. The solid fraction was extracted for DNA, PCR-amplified for the 16S rDNA gene of bacteria and archaea, sequenced and analyzed for bacteria and archaea diversity. The enteric methane emission data showed a decrease in the mitigation effect of AT over time (a 52—57% reduction in methane yield in experimental periods 1 and 2 for HAT and no statistical effect in P3 and P4). At the community level, both bacterial and archaeal communities were different (P < 0.05) between treatments. Methanosphaera differed between HAT and control with a significant reduction for HAT in P1, a smaller decrease in P2, and no difference from CON in P3 and P4, whereas Methanobrevibacter populations were unaltered. Butyrate-producing bacteria such as Butyrivibrio, Moryella, and Eubacterium were higher in HAT treatments compared with CON and ORE throughout the experiment. These findings indicate that AT selectively inhibits specific clades of methanogens such as Methanosphaera, which may have a greater share in total methane formation in the rumen than previously thought. Inhibition of methanogens was accompanied by significant alterations in the rumen bacterial populations revealing that alternate pathways of fermentation may be triggered with methane inhibition. This is the first study demonstrating the effect of AT on microbial interactions within the rumen and their relationship to methane emissions.

Keywords: methylotrophic methanogens, Asparagopsis taxiformis, dairy cow.