Unravelling the role of condensed tannins in ruminants using stable isotopes

Authors: DUBEUX, JOSE - University Of Florida; VAN CLEEF, FLAVIA - University Of Florida; RUIZ-MORENO, MARTIN - University Of Florida; NAUMANN, HARLEY - University Of Missouri; WHEELER, CHRISEE - University Of Missouri; SANTOS, ERICK - University Of Florida; Jaramillo, David; GARCIA, CARLOS - University Of Florida; SOLLENBERGER, LYNN - University Of Florida; VENDRAMINI, JOAO - University Of Florida; DILORENZO, NICOLAS - University Of Florida

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/12/2021
Publication Date: 11/12/2021
Citation: Dubeux, J., Van Cleef, F., Ruiz-Moreno, M., Naumann, H., Wheeler, C., Santos, E., Jaramillo, D.M., Garcia, C., Sollenberger, L., Vendramini, J., Dilorenzo, N. 2021. Unravelling the role of condensed tannins in ruminants using stable isotopes. Meeting Abstract. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT.

Interpretive Summary: Condensed tannins (CT) have numerous roles in ruminant nutrition, but there is limited knowledge on the CT dynamics in the gastrointestinal tract of ruminants. We conducted a series of experiments using a tannin-rich legume to determine intake and digestibility of CT in ruminants and their role on greenhouse gas emissions. In the in vivo trial, 25 Angus-crossbred steers were randomly assigned to treatments containing 0, 25, 50, 75, and 100% of ‘Au Grazer’ (SL, Lespedeza cuneata) hay, mixed with ‘Tifton-85’ bermudagrass hay (Cynodon spp.) to evaluate enteric CH4 emission and excreta GHG emission (CH4, N2O, and CO2). In the in vitro trials, we tracked CT digestibility using stable isotopes. Plants of SL were enriched with labeled 13C-CO2. Enteric CH4 was reduced when CT intake was greater and CT recovery in feces was lesser than CT intake. Dung GHG emissions were affected by sampling day, with first days presenting greatest emissions. Urinary GHG emissions were reduced in the first days after urine application when 100SL was fed to steers. Labeling of SL was successful, resulting in the enrichment of CT and of the fermentation end products. Carbon from CT was detected in end products of fermentation. Therefore, CT reduced in vivo and in vitro GHG emission from ruminants, and the isotopic analyses allow us to conclude that ruminal microorganisms digested CT.

Technical Abstract: Condensed tannins (CT) have numerous roles in ruminant nutrition, but there is limited knowledge on the CT dynamics in the gastrointestinal tract of ruminants. We conducted a series of experiments using a tannin-rich legume to determine intake and digestibility of CT in ruminants and their role on GHG emissions. In the in vivo trial, 25 Angus-crossbred steers were distributed in a randomized complete block design and randomly assigned to treatments containing 0, 25, 50, 75, and 100% of ‘Au Grazer’ [SL, Lespedeza cuneata (Dum. Cours.) G. Don] hay, mixed with ‘Tifton-85’ bermudagrass hay (Cynodon spp.) to evaluate enteric CH4 emission and excreta GHG emission (CH4, N2O, and CO2). In the in vitro trials, we tracked CT digestibility using stable isotopes of C, 13C. Plants of SL were enriched four times, for 10 consecutive days, 1 h per day, with labeled 13C-CO2. CT molecules were purified, and the pure extract analyzed for 13C. Pure CT, enriched SL, and alfalfa were used in a 48-h in vitro fermentation. End-products of fermentation (microbial mass, clarified rumen fluid, residue of rumen fluid, and CH4 produced) were analyzed for 13C. Enteric CH4 was reduced when CT intake was greater (P < 0.0001) and CT recovery in feces was lesser than CT intake. Dung GHG emissions were affected by sampling day (P < 0.0001), with first days presenting greatest emissions. Urine GHG emissions were reduced in the first days after urine application when 100SL was fed to steers (P < 0.0001). Labeling of SL was successful (P < 0.0001), resulting in the enrichment of CT (P = 0.002) and of the fermentation end products. Carbon from CT was detected in end products of fermentation. Therefore, CT reduced in vivo and in vitro GHG emission from ruminants, and the isotopic analyses allow us to conclude that ruminal microorganisms digested CT.