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This study investigated the effects of acacia (extract of Acacia mearnsii) and sainfoin (Onobrychis viciifolia) as condensed tannin (CT)-rich sources on ruminal and manure methane (CH 4) emissions in comparison with non-CT silages characterized by different contents of the cell wall and water-soluble carbohydrates. In a 3 × 6 incomplete Latin square design, 30 Holstein cows (63 ± 23 d in milk; mean ± SD; 33.8 ± 7.6 kg of milk per day, body weight 642 ± 81 kg) were provided with ad libitum access to 1 of 6 total mixed rations comprising 790 g of silage and 210 g of concentrate per kilogram of dry matter (DM). The silages were either rich in sainfoin [neutral detergent fiber (NDF): 349 g/kg of DM], perennial ryegrass (NDF: 420 g/kg of DM), or red clover (NDF: 357 g/kg of DM). Each silage was supplemented with 20 g/kg (of total diet DM) of acacia or straw meal. Feed intake and milk yield were recorded daily. Milk composition and ruminal fluid characteristics and microbiota were analyzed. The individual ruminal CH 4 production was determined using the GreenFeed system, and CH 4 emissions from the manure of cows fed the same diets were measured in a parallel experiment over 30 d at 25°C using a dynamic flux chamber. The CT sources did not reduce CH 4 yield or emission intensity. Acacia reduced milk production (from 26.3 to 23.2 kg/d) and DM intake (from 19.7 to 16.7 kg/d) when supplemented with ryegrass, and both CT sources reduced the milk protein content and yield. Acacia supplementation and ryegrass silage reduced the ruminal acetate:propionate ratio. Furthermore, during acacia treatment, the abundance of Methanobrevibacter archaea tended to be lower and that of Thermoplasmata was higher. Acacia reduced the CH 4 emissions from manure for the ryegrass group by 17% but not for the sainfoin and clover groups. Feeding sainfoin silage resulted in the lowest manure-derived CH 4 emissions (−47% compared with ryegrass). In conclusion, acacia reduced ruminal CH 4 production by 10%, but not emission intensity, and the mitigation effect of sainfoin depended on the silage to which it was compared. Because mitigation was partially associated with animal productivity losses, careful evaluation is required before the implementation of tanniferous feeds in farm practice. [Display omitted] [ABSTRACT FROM AUTHOR]

This study examined whether the effects of the tanniferous extract of Acacia mearnsii on N partitioning in dairy cows and ammonia (NH 3) volatilization from their excreta are additive to that of the tanniferous legume sainfoin (Onobrychis viciifolia) and remain consistent when supplemented to different silage types with varying crude protein (CP) content. In a 6 × 6 Latin Square arrangement, six multiparous Holstein cows (milk yield: 36.6 ± 3.9 kg/d; 70 ± 13 d in milk) were assigned randomly to six treatments. The experiment included a 14-d adaptation and a 7-d data collection period, where intake, milk yield, and composition were recorded daily and excreta were collected. Cows had ad libitum access to one of six total mixed rations containing (dry matter [DM] basis) 750 g/kg DM silage. The silages were rich in either sainfoin (180 g/kg CP of DM), ryegrass (118 g/kg CP) or clover (220 g/kg CP). Each silage was supplemented with 20 g/kg DM of Acacia mearnsii extract or straw meal. The effects on N partitioning, ruminal volatile fatty acids (VFA) and microbiota, and NH 3 volatilization from slurry reconstituted from fresh urine and feces were determined. The sainfoin-based diet reduced the apparent digestibility of organic matter, acid detergent fiber, and N compared with the ryegrass- and clover-based diets (P < 0.001). Acacia reduced the DM intake (P < 0.05) and apparent digestibility of organic matter and N across all silage types (P < 0.01). The digestibility of neutral detergent fiber was reduced with sainfoin, and ryegrass with Acacia (Silage × Acacia interaction P < 0.05). Acacia reduced the ruminal acetate proportion (P < 0.05) but did not affect ruminal propionate and n-butyrate or the microbiota composition. With ryegrass, the rumen fluid had lower acetate (P < 0.001) and greater n-butyrate proportions (P < 0.01) compared to sainfoin and clover, lower propionate proportions as compared with sainfoin (P < 0.05), and the lowest blood urea N concentration (P < 0.001). Acacia reduced energy-corrected milk yield (P < 0.05). Milk protein content was reduced with the sainfoin diet (P < 0.05). Sainfoin (compared to clover) and Acacia supplementation shifted the N excretion from urine to feces and decreased urinary urea N excretion and NH 3 volatilization from the slurry (P < 0.05). The effects of the two tannin sources were widely additive in mitigating urinary urea N and NH 3 volatilization. The results illustrate that combinatory N-abatement measures based on different CT sources are efficient, but supplementing Acacia resulted in decreasing dry matter intake and milk production, while sainfoin supplementation resulted in lower organic matter digestibility. [Display omitted] • Two tannin sources, sainfoin and Acacia mearnsii , were studied in dairy cows. • Sainfoin and Acacia were additive in reducing urinary N-losses. • Acacia reduced ammonia volatilization from fresh slurry by up to 37%. • The latter effect was greater at high dietary protein content. • Acacia reduced performance and sainfoin reduced digestibility. [ABSTRACT FROM AUTHOR]

Direct detection of highly reactive, atmospheric hydroxyl radicals (OH) is widely accomplished by laser-induced fluorescence (LIF) instruments. The technique is also suitable for the indirect measurement of HO2 and RO2 peroxy radicals by chemical conversion to OH. It requires sampling of ambient air into a low pressure cell, where OH fluorescence is detected after excitation by 308 nm laser radiation. Although the residence time of air inside the fluorescence cell is typically only on the order of milliseconds, there is potential that additional OH is internally produced, which would artificially increase the measured OH concentration. Here, we present experimental studies investigating potential interferences in the detection of OH and peroxy radicals for the LIF instruments of Forschungszentrum Jülich for nighttime conditions. For laboratory experiments, the inlet of the instrument was overflown by excess synthetic air containing one or more reactants. In order to distinguish between OH produced by reactions upstream of the inlet and artificial signals produced inside the instrument, a chemical titration for OH was applied. Additional experiments were performed in the simulation chamber SAPHIR where simultaneous measurements by an open-path differential optical absorption spectrometer (DOAS) served as reference for OH to quantify potential artifacts in the LIF instrument. Experiments included the investigation of potential interferences related to the nitrate radical (NO3, N2O5), related to the ozonolysis of alkenes (ethene, propene, 1-butene, 2,3-dimethyl-2-butene, α-pinene, limonene, isoprene), and the laser photolysis of acetone. Experiments studying the laser photolysis of acetone yield OH signals in the fluorescence cell, which are equivalent to 0.05 x 106 cm-3 OH for a mixing ratio of 5 ppbv acetone. Under most atmospheric conditions, this interference is negligible. No significant interferences were found for atmospheric concentrations of reactants during ozonolysis experiments. Only for α-pinene, limonene, and isoprene at reactant concentrations which are orders of magnitude higher than in the atmosphere artificial OH could be detected. The value of the interference depends on the turnover rate of the ozonolysis reaction. For example, an apparent OH concentration of approximately 1 x 106cm-3 is observed, if 5.8ppbv limonene reacts with 600ppbv ozone. Experiments with the nitrate radical NO3 reveal a small interference signal in the OH, HO2 and RO2 detection. Dependencies on experimental parameters point to artificial OH formation by surface reactions at the chamber walls or in molecular clusters in the gas expansion. The signal scales with the presence of NO3 giving equivalent radical concentrations of 1.1 x 105 cm-3 OH, 1 x 107 cm-3 HO2, and 1.7 x 107 cm-3 RO2 per 10 pptv NO3. [ABSTRACT FROM AUTHOR]