95 research outputs found
Rumen fermentation parameters and papillae development in Simmental growing bulls with divergent residual feed intake
Residual feed intake (RFI), a widespread index used to measure animal feed efficiency, is influenced by various individual biological factors related to inter-animal variation that need to be assessed. Herein, 30 Simmental bulls, raised under the same farm conditions, were divided on the basis of RFI values into a high efficient group (HE, RFI = − 1.18 ± 0.33 kg DM/d, n = 15) and a low efficient group (LE, RFI = 0.92 ± 0.35 kg DM/d, n = 15). Subsequently, bulls were slaughtered at an average BW of 734 ± 39.4 kg. Their ruminal fermentation traits were analysed immediately after slaughtering and after 24 h of in vitro incubation. Furthermore, ruminal micro-biota composition and ruminal papillae morphology were examined. The LE group exhibited a higher propionate concentration as a percentage of total volatile fatty acids (17.3 vs 16.1%, P = 0.04) in the rumen fluid collected during slaughtering, which was also confirmed after in vitro fermentation (16.6 vs 15.4% respectively for LE and HE, P = 0.01). This phenomenon resulted in a significant alteration in the acetate−to−propionate ratio (A:P) with higher values for the HE group, both after slaughter (4.01 vs 3.66, P = 0.02) and after in vitro incubation (3.78 vs 3.66, P = 0.02). Methane production was similar in both groups either as absolute production (227 vs 218 mL for HE and LE, respectively) or expressed as a percentage of total gas (approximately 22%). Even if significant differences (P < 0.20) in the relative abundance of some bacterial genera were observed for the two RFI groups, no significant variations were observed in the alpha (Shannon index) and beta (Bray–Curtis index) diversity. Considering the papillae morphology, the LE subjects have shown higher length values (6.26 vs 4.90 mm, P < 0.01) while HE subjects have demonstrated higher papillae density (46.4 vs 40.5 n/cm2, P = 0.02). Histo-morphometric analysis did not reveal appreciable modifications in the total papilla thickness, boundaries or surface between the experimental groups. In conclusion, our results contribute to efforts to analyse the factors affecting feed efficiency at the ruminal level. Propionate production, papillae morphology and a few bacterial genera certainly play a role in this regard, although not a decisive one
A new equipment for continuous measurement of methane production in a batch in vitro rumen system
A new rumen batch fermentation system that allows continuous measures of total gas (GP) and methane production (MP) was tested. The fermentation system is composed of glass bottles connected to gas counters (Ritter Apparatebau GmbH & Co. KG) and an infrared gas analyser that measures the methane concentration. The system allows direct and continuous measurement of GP and MP for accurate kinetic studies. The aim of the work was to test the rumen fermentation system and compare the GP and MP kinetics obtained. Barley meal (BM), alfalfa hay (AH), corn silage (CS), and soya bean hulls (SH) were used as substrates in four consecutive fermentation runs. Cumulative volumes of GP and MP and the percentage of methane on total GP were recorded continuously until 48 h and average values at 1 h intervals were fitted with an exponential model with a lag phase reaching a good fit (R2 > 0.992). GP and MP reached the highest plateau levels for SH (1836 and 370 ml, respectively; p < 0.01) and the lowest for AH (1000 and 233 ml, respectively). The remaining substrates showed intermediate values. MP kinetics showed a discrete lag phase (from 0.09 to 1.12 h), whereas it was equal to zero for the total GP (except for SH). The methane concentration in gas flowing increased rapidly at the beginning of fermentation (from 0.35 to 0.95 h−1) and reached a plateau after approximately 8–12 h. In conclusion, the rumen fermentation system evaluated generates methane data comparable to those reported in the literature and allows simple continuous measurement of methane release throughout fermentation
Indirect ultraviolet photodesorption from CO:N2 binary ices - an efficient grain-gas process
UV ice photodesorption is an important non-thermal desorption pathway in many
interstellar environments that has been invoked to explain observations of cold
molecules in disks, clouds and cloud cores. Systematic laboratory studies of
the photodesorption rates, between 7 and 14 eV, from CO:N2 binary ices, have
been performed at the DESIRS vacuum UV beamline of the synchrotron facility
SOLEIL. The photodesorption spectral analysis demonstrates that the
photodesorption process is indirect, i.e. the desorption is induced by a photon
absorption in sub-surface molecular layers, while only surface molecules are
actually desorbing. The photodesorption spectra of CO and N2 in binary ices
therefore depend on the absorption spectra of the dominant species in the
subsurface ice layer, which implies that the photodesorption efficiency and
energy dependence are dramatically different for mixed and layered ices
compared to pure ices. In particular, a thin (1-2 ML) N2 ice layer on top of CO
will effectively quench CO photodesorption, while enhancing N2 photodesorption
by a factors of a few (compared to the pure ices) when the ice is exposed to a
typical dark cloud UV field, which may help to explain the different
distributions of CO and N2H+ in molecular cloud cores. This indirect
photodesorption mechanism may also explain observations of small amounts of
complex organics in cold interstellar environments.Comment: 21 pages 5 figure
Effect of heat stress on dairy cow performance and on expression of protein metabolism genes in mammary cells
The aim of this study was to assess the effect of heat stress on dairy cow performance and on the expression of selected genes involved in milk protein metabolism. Eight Italian Holstein Friesian cows were kept under thermoneutral conditions (temperature\u2013humidity index (THI) 0.05), CSN3 (p > 0.05), HSPA8 (p > 0.05), and STAT5B (p > 0.05) mRNA. Mild heat stress reduced the performance of dairy cows without affecting the expression of genes coding for caseins
Heat stress and feeding behaviour of dairy cows in late lactation
Heat stress is one of the most important problems that dairy cows have to face and the use of cooling systems is becoming more and more important. The first reaction that has the animal to cope with the environmental variations is to modify its behaviour. This study was aimed to investigate the effect of heat stress and a cooling system on the feeding behaviour of Italian Holstein Friesian dairy cows in late lactation. Two experiments were performed. In the first experiment, eight dairy cows were firstly kept 7 d under thermoneutral condition, and then under mild heat stress (temperature humidity index, THI, ranging between 72 and 78) for others 7 d. The second experiment consisted of 8 dairy cows used in a two-period cross-over design where the treatment was the use or not of a sprinkler system for cooling cows under mild heat stress. Cows were equipped with a noseband pressure sensor able to detect rumination and eating time, number of rumination and eating chews, number of rumination boluses and rumination intensity. Heat stress reduced rumination time, number of rumination chews and boluses (p <.05), and tended to reduce the number of eating chews (p <.10). Cooled cows increased rumination and eating time (p <.05), rumination intensity (p <.01), and the number of rumination and eating chews (p <.05). In conclusion, feeding behaviour was deeply influenced even by mild heat stress, which was effectively improved by the use of a sprinkler system.HIGHLIGHTS Mild heat stress reduced rumination time, number of rumination chews and boluses of dairy cows in late lactation Cooling cows with sprinklers was effective in alleviating heat stress in terms of feeding behaviour
SURFRESIDE2: An ultrahigh vacuum system for the investigation of surface reaction routes of interstellar interest
A new ultrahigh vacuum experiment is described to study atom and radical addition reactions in interstellar ice analogues for astronomically relevant temperatures. The new setup – SURFace REaction SImulation DEvice (SURFRESIDE2) – allows a systematic investigation of solid state pathways resulting in the formation of molecules of astrophysical interest. The implementation of a double beam line makes it possible to expose deposited ice molecules to different atoms and/or radicals sequentially or at the same time. Special efforts are made to perform experiments under fully controlled laboratory conditions, including precise atom flux determinations, in order to characterize reaction channels quantitatively. In this way, we can compare and combine different surface reaction channels with the aim to unravel the solid state processes at play in space. Results are constrained in situ by means of a Fourier transform infrared spectrometer and a quadrupole mass spectrometer using reflection absorption infrared spectroscopy and temperature programmed desorption, respectively. The performance of the new setup is demonstrated on the example of carbon dioxide formation by comparing the efficiency through two different solid state channels (CO + OH → CO_2 + H and CO + O → CO_2) for which different addition products are needed. The potential of SURFRESIDE2 to study complex molecule formation, including nitrogen containing (prebiotic) compounds, is discussed
Wavelength-Dependent UV Photodesorption of Pure and Ices
Context: Ultraviolet photodesorption of molecules from icy interstellar grains can explain observations of cold gas in regions where thermal desorption is negligible. This non-thermal desorption mechanism should be especially important where UV fluxes are high. Aims: and are expected to play key roles in astrochemical reaction networks, both in the solid state and in the gas phase. Measurements of the wavelength-dependent photodesorption rates of these two infrared-inactive molecules provide astronomical and physical-chemical insights into the conditions required for their photodesorption.
Methods: Tunable radiation from the DESIRS beamline at the SOLEIL synchrotron in the astrophysically relevant 7 to 13.6 eV range is used to irradiate pure and thin ice films. Photodesorption of molecules is monitored through quadrupole mass spectrometry. Absolute rates are calculated by using the well-calibrated CO photodesorption rates. Strategic and isotopolog mixtures are used to investigate the importance of dissociation upon irradiation. Results: photodesorption mainly occurs through excitation of the state and subsequent desorption of surface molecules. The observed vibronic structure in the photodesorption spectrum, together with the absence of formation, supports that the photodesorption mechanism of is similar to CO, i.e., an indirect DIET (Desorption Induced by Electronic Transition) process without dissociation of the desorbing molecule. In contrast, photodesorption in the 7−13.6 eV range occurs through dissociation and presents no vibrational structure. Conclusions: Photodesorption rates of and integrated over the far-UV field from various star-forming environments are lower than for CO. Rates vary between and photodesorbed molecules per incoming photon.Astronom
Photoionization spectroscopy of CH3C3N in the vacuum-ultraviolet range
International audienceUsing vacuum-ultraviolet (VUV) synchrotron radiation, threshold and dissociative photoionization of cyanopropyne (CH3C3N) in the gas phase have been studied from 86 000 cm−1 up to 180 000 cm−1 by recording Threshold-PhotoElectron Spectrum (TPES) and PhotoIon Yield (PIY). Ionization energies of the four lowest electronic states X̃+2E,Ã+2A1,B̃+2E and C̃+ of CH3C3N+ are derived from the TPES with a better accuracy than previously reported. The adiabatic ionization potential of CH3C3N is measured as 86872±20 cm−1. A description of the vibrational structure of these states is proposed leading to the first determination of the vibrational frequencies for most modes. The vibrational assignments of the X̃+ state are supported by density functional theory calculations. In addition, dissociative photoionization spectra have been recorded for several cationic fragments in the range 12–15.5 eV (96 790–125 000 cm−1) and they bring new information on the photophysics of CH3C3N+. Threshold energies for the cationic dissociative channels leading to CH2C3N+, CHC3N+, HC3H+, HCNH+ and CH3+ have been measured for the first time and are compared with quantum chemical calculations
Laboratory evidence for efficient water formation in interstellar ices
Even though water is the main constituent in interstellar icy mantles, its
chemical origin is not well understood. Three different formation routes have
been proposed following hydrogenation of O, O2, or O3, but experimental
evidence is largely lacking. We present a solid state astrochemical laboratory
study in which one of these routes is tested. For this purpose O2 ice is
bombarded by H- or D-atoms under ultra high vacuum conditions at astronomically
relevant temperatures ranging from 12 to 28 K. The use of reflection absorption
infrared spectroscopy (RAIRS) permits derivation of reaction rates and shows
efficient formation of H2O (D2O) with a rate that is surprisingly independent
of temperature. This formation route converts O2 into H2O via H2O2 and is found
to be orders of magnitude more efficient than previously assumed. It should
therefore be considered as an important channel for interstellar water ice
formation as illustrated by astrochemical model calculations.Comment: 15 pages, 4 figures. ApJ, in pres
Indirect Ultraviolet Photodesorption from CO:N2 Binary Ices — An Efficient Grain-Gas Process
Ultraviolet (UV) ice photodesorption is an important non-thermal desorption pathway in many interstellar environments that has been invoked to explain observations of cold molecules in disks, clouds, and cloud cores. Systematic laboratory studies of the photodesorption rates, between 7 and 14 eV, from CO:N2 binary ices, have been performed at the DESIRS vacuum UV beamline of the synchrotron facility SOLEIL. The photodesorption spectral analysis demonstrates that the photodesorption process is indirect, i.e., the desorption is induced by a photon absorption in sub-surface molecular layers, while only surface molecules are actually desorbing. The photodesorption spectra of CO and N2 in binary ices therefore depend on the absorption spectra of the dominant species in the sub-surface ice layer, which implies that the photodesorption efficiency and energy dependence are dramatically different for mixed and layered ices compared with pure ices. In particular, a thin (1-2 ML) N2 ice layer on top of CO will effectively quench CO photodesorption, while enhancing N2 photodesorption by a factor of a few (compared with the pure ices) when the ice is exposed to a typical dark cloud UV field, which may help to explain the different distributions of CO and N2H+ in molecular cloud cores. This indirect photodesorption mechanism may also explain observations of small amounts of complex organics in cold interstellar environments.Astronom
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