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J Dairy Sci

Title:		"Exhaled volatile fatty acids, ruminal methane emission, and their diurnal patterns in lactating dairy cows"
Author(s):		Islam MZ; Giannoukos S; Raisanen SE; Wang K; Ma X; Wahl F; Zenobi R; Niu M;
Address:		"ETH Zurich, Department of Environmental Systems Science, Institute of Agricultural Sciences, 8092 Zurich, Switzerland. ETH Zurich, Department of Chemistry and Applied Biosciences, Analytical Chemistry, 8093 Zurich, Switzerland. Electronic address: stamatios.giannoukos@org.chem.ethz.ch. Food Microbial Systems Research Division, Agroscope, 3003 Bern, Switzerland. ETH Zurich, Department of Chemistry and Applied Biosciences, Analytical Chemistry, 8093 Zurich, Switzerland. ETH Zurich, Department of Environmental Systems Science, Institute of Agricultural Sciences, 8092 Zurich, Switzerland. Electronic address: mutian.niu@usys.ethz.ch"
Journal Title:		J Dairy Sci
Year:		2023
Volume:		20230518
Issue:		10
Page Number:		6849 - 6859
DOI:		10.3168/jds.2023-23301
ISSN/ISBN:		1525-3198 (Electronic) 0022-0302 (Linking)
Abstract:		"To date, the commonly used methods to assess rumen fermentation are invasive. Exhaled breath contains hundreds of volatile organic compounds (VOC) that can reflect animal physiological processes. In the present study, for the first time, we aimed to use a noninvasive metabolomics approach based on high-resolution mass spectrometry to identify rumen fermentation parameters in dairy cows. Enteric methane (CH(4)) production from 7 lactating cows was measured 8 times over 3 consecutive days using the GreenFeed system (C-Lock Technology Inc.). Simultaneously, exhalome samples were collected in Tedlar gas sampling bags and analyzed offline using a secondary electrospray ionization high-resolution mass spectrometry system. In total, 1,298 features were detected, among them targeted exhaled volatile fatty acids (eVFA; i.e., acetate, propionate, butyrate), which were putatively annotated using their exact mass-to-charge ratio. The intensity of eVFA, in particular acetate, increased immediately after feeding and followed a similar pattern to that observed for ruminal CH(4) production. The average total eVFA concentration was 35.5 count per second (CPS), and among the individual eVFA, acetate had the greatest concentration, averaging 21.3 CPS, followed by propionate at 11.5 CPS, and butyrate at 2.67 CPS. Further, exhaled acetate was on average the most abundant of the individual eVFA at around 59.3%, followed by 32.5 and 7.9% of the total eVFA for propionate and butyrate, respectively. This corresponds well with the previously reported proportions of these VFA in the rumen. The diurnal patterns of ruminal CH(4) emission and individual eVFA were characterized using a linear mixed model with cosine function fit. The model characterized similar diurnal patterns for eVFA and ruminal CH(4) and H(2) production. Regarding the diurnal patterns of eVFA, the phase (time of peak) of butyrate occurred first, followed by that of acetate and propionate. Importantly, the phase of total eVFA occurred around 1 h before that of ruminal CH(4). This corresponds well with existing data on the relationship between rumen VFA production and CH(4) formation. Results from the present study revealed a great potential to assess the rumen fermentation of dairy cows using exhaled metabolites as a noninvasive proxy for rumen VFA. Further validation, with comparisons to rumen fluid, and establishment of the proposed method are required"
Keywords:		"Female Cattle Animals *Lactation *Propionates/metabolism Milk/chemistry Methane/metabolism Diet/veterinary Rumen/metabolism Fatty Acids, Volatile/metabolism Butyrates/metabolism Fermentation Fatty Acids/analysis bovine exhalome exhaled volatile fatty acid;"
Notes:		"MedlineIslam, M Z Giannoukos, S Raisanen, S E Wang, K Ma, X Wahl, F Zenobi, R Niu, M eng 2023/05/21 J Dairy Sci. 2023 Oct; 106(10):6849-6859. doi: 10.3168/jds.2023-23301. Epub 2023 May 18"