Indications for a lower methane yield from digested fibre in ruminants digesting fibre more efficiently

It is assumed that the absolute amount of methane (CH4) produced on a given diet increases proportionately (i.e., in a linear manner) with the amount of digested fibre. Therefore, the CH4 yield per unit of digested fibre is considered constant for a given diet. This conceptually matches findings of lower digestibility in low-CH4 emitting animals, and of lower CH4 yield at higher intake levels due to shorter digesta passage and hence reduced digestibility. Irrespective of these observations, this general assumption was challenged by findings in one study where CH4 yield per unit of digested fibre had unexpectedly declined in individuals digesting the fibre provided by the same diet more efficiently. To investigate this finding in more detail, we collated a dataset from 16 studies with cattle and sheep with a total of 61 forage-based diet groups consisting of at least five animals each (472 animals in total). We assessed whether there was a linear relationship between the daily CH4 emission and the amount of digested fibre, both within the same and across the different diet groups. Across diets, CH4 emissions did not increase linearly with the amount of digested neutral or acid detergent fibre in either species. Within diet groups, the majority of cases also showed evidence for less-than-linear increase of CH4 emissions with increasing amount of digested neutral or acid detergent fibre, even though the 95 % confidence intervals could not rule out a linear relationship in many cases. Reasons why this phenomenon was not described earlier may include that the great individual variation associated with an accumulation of errors in the variables concerned often prevented statistical significance in individual studies. Although the findings across diets concerning the variation in CH4 yield per unit of digested fibre do not exclude some diet-specific effects, the within-diet assessment clearly points towards individual animal effects in microbial fibre digestion in a way that CH4 production is proportionately lower when fibre is digested more efficiently. Mechanistically, animals with a more efficient fibre digestion might produce volatile fatty acids at a higher rate and have a locally lower ruminal pH, favouring microbiota of propionate-producing pathways. The presence of animal-individual differences in CH4 yield per unit of digested fibre with varying efficiency of fibre fermentation should be confirmed in a specific experiment where also the reasons for such a phenomenon are further investigated

Indications for a lower methane yield from digested fibre in ruminants digesting fibre more efficiently

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Effects of graded levels of dietary pomegranate peel on methane and nitrogen losses, and metabolic and health indicators in dairy cows

This study aimed to quantify the effects of dietary inclusion of tannin-rich pomegranate peel (PP) on intake, methane and nitrogen (N) losses, and metabolic and health indicators in dairy cows. Four multiparous, late-lactating Brown Swiss dairy cows (796 kg body weight; 29 kg/d of energy corrected milk yield) were randomly allocated to 3 treatments in a randomized cyclic change-over design with 3 periods, each comprising 14 d of adaptation, 7 d of milk, urine, and feces collection, and 2 d of methane measurements. Treatments were formulated using PP that replaced on a dry matter (DM) basis 0% (control), 5%, and 10% of the basal mixed ration (BMR) consisting of corn and grass silage, alfalfa, and concentrate. Gaseous exchange of the cows was determined in open-circuit respiration chambers. Blood samples were collected on d 15 of each period. Individual feed intake as well as feces and urine excretion were quantified, and representative samples were collected for analyses of nutrients and phenol composition. Milk was analyzed for concentrations of fat, protein, lactose, milk urea N, and fatty acids. Total phenols and antioxidant capacity in milk and plasma were determined. In serum, the concentrations of urea and bilirubin as well as the activities of alanine aminotransferase (ALT), aspartate aminotransferase, glutamate dehydrogenase, alkaline phosphatase, and γ-glutamyl transferase were measured. The data was subjected to ANOVA with the Mixed procedure of SAS, with treatment and period as fixed and animal as random effects. The PP and BMR contained 218 and 3.5 g total extractable tannins per kg DM, respectively, and thereof 203 and 3.3 g hydrolyzable tannins. Total DM intake, energy corrected milk, and methane emission (total, yield, and intensity) were not affected by PP supplementation. The proportions of C18:2 n-6 and C18:3 n-3 in milk increased linearly as the amount of PP increased in the diet. Milk urea N, blood urea N, and urinary N excretion decreased linearly with the increase in dietary PP content. Total phenols and antioxidant capacity in milk and plasma were not affected by the inclusion of PP. The activity of ALT increased in a linear manner with the inclusion of PP. In conclusion, replacing up to 10% of BMR with PP improved milk fatty acid composition and alleviated metabolic and environmental N load. However, the elevated serum ALT activity indicates an onset of liver stress even at 5% PP, requiring the development of adaptation protocols for safe inclusion of PP in ruminant diets

Effects of graded levels of dietary pomegranate peel on methane and nitrogen losses, and metabolic and health indicators in dairy cows

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Spectral and Timing Analysis of the accretion-powered pulsar 4U 1626-67 observed with Suzaku and NuSTAR

We present an analysis of the spectral shape and pulse profile of the accretion-powered pulsar 4U 1626-67 observed with Suzaku and NuSTAR during a spin-up state. The pulsar, which experienced a torque reversal to spin-up in 2008, has a spin period of 7.7 s. Comparing the phase-averaged spectra obtained with Suzaku in 2010 and with NuSTAR in 2015, we find that the spectral shape changed between the two observations: the 3-10 keV flux increased by 5% while the 30-60 keV flux decreased significantly by 35%. Phase-averaged and phase-resolved spectral analysis shows that the continuum spectrum observed by NuSTAR is well described by an empirical NPEX continuum with an added broad Gaussian emission component around the spectral peak at 20 keV. Taken together with the observed Pdot value obtained from Fermi/GBM, we conclude that the spectral change between the Suzaku and NuSTAR observations was likely caused by an increase of the accretion rate. We also report the possible detection of asymmetry in the profile of the fundamental cyclotron line. Furthermore, we present a study of the energy-resolved pulse profiles using a new relativistic ray tracing code, where we perform a simultaneous fit to the pulse profiles assuming a two-column geometry with a mixed pencil- and fan-beam emission pattern. The resulting pulse profile decompositions enable us to obtain geometrical parameters of accretion columns (inclination, azimuthal and polar angles) and a fiducial set of beam patterns. This information is important to validate the theoretical predictions from radiation transfer in a strong magnetic field.Comment: 19 pages, 14 figures, Accepted for publication in ApJ on May 5, 201

Influence of ruminal methane on digesta retention and digestive physiology in non-lactating dairy cattle

Enteric methane (CH4) production is a side-effect of herbivore digestion, but it is unknown whether CH4 itself influences digestive physiology. We investigated the effect of adding CH4 to, or reducing it in, the reticulorumen (RR) in a 4 × 4 Latin square experiment with rumen-fistulated, non-lactating cows, with four treatments: (i) control, (ii) insufflation of CH4 (iCH4), (iii) N via rumen fistula, (iv) reduction of CH4 via administration of bromochloromethane (BCM). DM intake (DMI), apparent total tract digestibility, digesta mean retention times (MRT), rumen motility and chewing activity, spot breath CH4 emission (CH4exhal, litre/kg DMI) as well as CH4 dissolved in rumen fluid (CH4RRf, μg/ml) were measured. Data were analysed using mixed models, including treatment (or, alternatively, CH4exhal or CH4RRf) and DMI relative to body mass0·85 (rDMI) as covariates. rDMI was the lowest on the BCM treatment. CH4exhal was highest for iCH4 and lowest for BCM treatments, whereas only BCM affected (reduced) CH4RRf. After adjusting for rDMI, CH4RRf had a negative association with MRT in the gastrointestinal tract but not in the RR, and negative associations with fibre digestibility and measures of rumination activity. Adjusting for rDMI, CH4exhal had additionally a negative association with particle MRT in the RR and a positive association with rumen motility. Thus, higher rumen levels of CH4 (CH4exhal or CH4RRf) were associated with shorter MRT and increased motility. These findings are tentatively interpreted as a feedback mechanism in the ruminant digestive tract that aims at mitigating CH4 losses by shortening MRT at higher CH4

The Goodness of Simultaneous Fits in ISIS

In a previous work, we introduced a tool for analyzing multiple datasets simultaneously, which has been implemented into ISIS. This tool was used to fit many spectra of X-ray binaries. However, the large number of degrees of freedom and individual datasets raise an issue about a good measure for a simultaneous fit quality. We present three ways to check the goodness of these fits: we investigate the goodness of each fit in all datasets, we define a combined goodness exploiting the logical structure of a simultaneous fit, and we stack the fit residuals of all datasets to detect weak features. These tools are applied to all RXTE-spectra from GRO 1008−57, revealing calibration features that are not detected significantly in any single spectrum. Stacking the residuals from the best-fit model for the Vela X-1 and XTE J1859+083 data evidences fluorescent emission lines that would have gone undetected otherwise.M. Kühnel was supported by the Bundesministerium für Wirtschaft und Technologie under Deutsches Zentrum für Luft- und Raumfahrt grants 50OR1113 and 50OR1207

The giant outburst of 4U 0115+634 in 2011 with Suzaku and RXTE - Minimizing cyclotron line biases

We present an analysis of X-ray spectra of the high-mass X-ray binary 4U 0115+634 as observed with Suzaku and RXTE in 2011 July, during the fading phase of a giant X-ray outburst. We used a continuum model consisting of an absorbed cutoff power law and an ad hoc Gaussian emission feature centered around 8.5 keV, which we attribute to cyclotron emission. Our results are consistent with a fundamental cyclotron absorption line centered at ∼10.2 keV for all observed flux ranges. At the same time we rule out significant influence of the 8.5 kev Gaussian on the parameters of the cyclotron resonant scattering feature, which are not consistent with the cyclotron line energies or the depths of previously reported flux-dependent descriptions. We also show that some continuum models can lead to artificial line-like residuals in the analyzed spectra, which are then misinterpreted as unphysically strong cyclotron lines. Specifically, our results do not support the existence of a previously claimed additional cyclotron feature at ∼15 keV. Apart from these features, we find for the first time evidence for a He-like Fe XXV emission line at ∼6.7 keV and weak H-like Fe XXVI emission close to ∼7.0 keV.We acknowledge funding by the European Space Agency under contract number C4000115860/15/NL/IB, by the Bundesministerium für Wirtschaft und Technologie under Deutsches Zentrum für Luft- und Raumfahrt grants 50OR0808, 50OR0905, 50OR1113, and 50OR1207, and by the Deutscher Akademischer Austauschdienst. MTW is supported by the NASA Astrophysical Data Analysis Program and the Chief of Naval Research. VG is supported through the Margarethe von Wrangell fellowship by the ESF and the Ministry of Science, Research and the Arts Baden-Württemberg. SMN and JMT acknowledge Spanish Ministerio de Ciencia, Tecnología e Innovación (MICINN) through the grant ESP2016-76683-C3-1-R and ESP2017-85691-P, respectively