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- Danielsson, Rebecca, et al.
(author)
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Compound- and context-dependent effects of antibiotics on greenhouse gas emissions from livestock
- 2019
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In: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 6
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Journal article (peer-reviewed)abstract
- The use of antibiotics in livestock production may trigger ecosystem disservices, including increased emissions of greenhouse gases. To evaluate this, we conducted two separate animal experiments, administering two widely used antibiotic compounds (benzylpenicillin and tetracycline) to dairy cows over a 4- or 5-day period locally and/or systemically. We then recorded enteric methane production, total gas production from dung decomposing under aerobic versus anaerobic conditions, prokaryotic community composition in rumen and dung, and accompanying changes in nutrient intake, rumen fermentation, and digestibility resulting from antibiotic administration. The focal antibiotics had no detectable effect on gas emissions from enteric fermentation or dung in aerobic conditions, while they decreased total gas production from anaerobic dung. Microbiome-level effects of benzylpenicillin proved markedly different from those previously recorded for tetracycline in dung, and did not differ by the mode of administration (local or systemic). Antibiotic effects on gas production differed substantially between dung maintained under aerobic versus anaerobic conditions and between compounds. These findings demonstrate compound- and context-dependent impacts of antibiotics on methane emissions and underlying processes, and highlight the need for a global synthesis of data on agricultural antibiotic use before understanding their climatic impacts.
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| 3. |
- Danielsson, Rebecca, et al.
(author)
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Evaluation of a gas in vitro system for predicting methane production in vivo
- 2017
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In: Journal of Dairy Science. - : American Dairy Science Association. - 0022-0302 .- 1525-3198. ; 100, s. 8881-8894
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Journal article (peer-reviewed)abstract
- Methane production from ruminant livestock varies with the diet as a result of factors such as dry matter intake, diet composition, and digestibility. To estimate the effect of dietary composition and feed additives, CH4 production can be measured in vitro as a first step because large numbers of samples can be incubated and analyzed at the same time. This study evaluated a recently developed in vitro method for prediction of in vivo CH4 production by examining the relationship between predicted and observed CH4 production values. A total of 49 different diets (observations), used in previous 13 in vivo studies, were selected to include diets varying in nutrient composition. Methane production was measured in all in vivo studies by respiration chambers or the GreenFeed system (C-Lock Inc., Rapid City, SD). Overall, the in vitro system predicted CH4 production well (R-2 = 0.96), but the values obtained were slightly underestimated compared with observed in vivo values (mean 399 L/d compared with 418 L/d: root mean square prediction error = 51.6 L/d or 12.3% of observed mean). Further analysis of the effect on residuals showed no significant relationship between CH4 production and most factors known to affect CH4 production such as dry matter intake, digestibility, and dietary concentrations of fat and starch. However, some factors included in the model were not well predicted by the system, with residuals negatively related to neutral detergent fiber concentration and positively related to concentrate proportion. The in vitro system can thus be useful for screening diets and evaluation of feed additives as a first step that can be best interpreted when feeding cows at maintenance level.
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| 4. |
- Danielsson, Rebecca, et al.
(author)
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Methane Production in Dairy Cows Correlates with Rumen Methanogenic and Bacterial Community Structure
- 2017
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In: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 8
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Journal article (peer-reviewed)abstract
- Methane (CH4) is produced as an end product from feed fermentation in the rumen. Yield of CH4 varies between individuals despite identical feeding conditions. To get a better understanding of factors behind the individual variation, 73 dairy cows given the same feed but differing in CH4 emissions were investigated with focus on fiber digestion, fermentation end products and bacterial and archaeal composition. In total 21 cows (12 Holstein, 9 Swedish Red) identified as persistent low, medium or high CH4 emitters over a 3 month period were furthermore chosen for analysis of microbial community structure in rumen fluid. This was assessed by sequencing the V4 region of 16S rRNA gene and by quantitative qPCR of targeted Methanobrevibacter groups. The results showed a positive correlation between low CH4 emitters and higher abundance of Methanobrevibacter ruminantium clade. Principal coordinate analysis (PCoA) on operational taxonomic unit (OTU) level of bacteria showed two distinct clusters (P < 0.01) that were related to CH4 production. One cluster was associated with low CH4 production (referred to as cluster L) whereas the other cluster was associated with high CH4 production (cluster H) and the medium emitters occurred in both clusters. The differences between clusters were primarily linked to differential abundances of certain OTUs belonging to Prevotella. Moreover, several OTUs belonging to the family Succinivibrionaceae were dominant in samples belonging to cluster L. Fermentation pattern of volatile fatty acids showed that proportion of propionate was higher in cluster L, while proportion of butyrate was higher in cluster H. No difference was found in milk production or organic matter digestibility between cows. Cows in cluster L had lower CH4/kg energy corrected milk (ECM) compared to cows in cluster H, 8.3 compared to 9.7 g CH4/kg ECM, showing that low CH4 cows utilized the feed more efficient for milk production which might indicate a more efficient microbial population or host genetic differences that is reflected in bacterial and archaeal (or methanogens) populations.
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| 5. |
- Danielsson, Rebecca
(author)
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Methane production in dairy cows : impact of feed and rumen microbiota
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Greenhouse gas emissions from the agricultural sector represent about 14.5% of total emissions related to human activity. Approximately 40% of agricultural sector emissions derive from enteric methane (CH₄) production by ruminants, due to their microbial digestion of feed. Level of CH₄ production varies according to feed type, feed intake and even among individual animals raised under similar conditions, but the underlying mechanism is not well known. This thesis investigated the effects of feed, feed additives, and rumen microbiota on CH₄ production within dairy cows and in a gas in vitro system. Effect of individual cow was stronger than effect of diet for both CH₄ production and methanogenic population when two different levels of forage proportions were fed. Dividing Methanobrevibacter species into two groups better explained the variation in CH₄ production. The effect of individual was evaluated in cows fed the same diet during mid-lactation. High, low and medium emitters were identified and selected for further studies on rumen microbiota. These revealed that CH₄ production was associated with archaeal and bacterial community structure. Differences were observed in volatile fatty acid proportions between communities, but not in fibre digestion or milk production. Tests on feed additives, cashew nut shell extract (CNSE) and glycerol in a gas in vitro system for their ability to reduce CH₄ production showed that CNSE reduced CH₄ production by 18% and had a strong impact on microbiota, while glycerol increased CH₄ production by 12% and had less effect on microbiota compared with the control. Comparison of microbial composition in inoculum from the in vitro control and in inoculum from the donor cow before incubation revealed that the bacterial community was relatively similar, while relative abundance of some species changed for archaeal population. This effect of transfer into another system should be considered when evaluating in vitro data. Evaluation of the in vitro system by comparing predicted and observed CH₄ production on 49 test diets showed an overall good relationship, with small root mean square error for prediction (12.3% and 9.5% of observed mean for fixed and mixed models, respectively). However, the in vitro system had limitations in prediction of concentrate proportion.
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