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Dynamics of in vitro rumen methane production after nitrate addition
Full text linkThe present study aimed to assess the dynamics of rumen methane (CH4) production following the addition of NaNO3. This was done using an in vitro rumen fermentation system that ensures continuous gas and methane assessments. Four different levels of NaNO3 were used to get the final nitrate concentrations of 0.5, 1.0, 1.5, and 2.0 mg/ml of rumen fluid. For each dose, corresponding controls contained sodium chloride and urea were realised to ensure comparable levels of sodium and nitrogen. The addition of nitrates had slight effect on the intensity of fermentation because the total gas produced minus CH4 (total methane-free gas) only went down at the highest dose (2.0 mg/ml), and the final concentrations of SCFA were the same at all doses. The most evident effect was a modification of the SCFA profile (low concentrations of propionate and valerate, progressive increments of acetate, and decreases of butyrate) and a reduction in overall CH4 production. The CH4 yield for the 0.5 mg/ml dose was not different from control in the entire fermentation. Yield of the 1.0 mg/ml dose was significantly lower than the control group (p < 0.05) only within the initial 24-h period, and higher dosages (1.5 and 2.0 mg/ml) were lower during the entire fermentation (p < 0.01). Methane yields were well fitted with the Gompertz model, but only the highest level of nitrate inclusion had a significant impact on the majority of model parameters (p < 0.01). The linear regressions between CH4 yields (y) and the amounts of nitrates (x) at progressive fermentation durations (e.g. 6, 12, 24, and 48 h) produced equations with increasing absolute slopes (from −0.069 to −0.517 ml/mg of nitrate). Therefore, nitrate reduced rumen CH4 yield in a dose-dependent manner: the impact of low doses was primarily observed at the initial stages of fermentation, whereas high doses exhibited effectiveness throughout the entire fermentation process. In conclusion, in batch fermentation systems, the dose effect of nitrates on methane yield was time dependent
Rumen fermentation parameters and papillae development in Simmental growing bulls with divergent residual feed intake
Full text linkResidual 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
Alpine pasture plant species affect in vitro rumen methane production and kinetics
Full text linkThis study aimed to evaluate the influence of different plant species widespread in alpine pastures on in vitro rumen fermentation parameters and methane kinetic production. A total of 11 plant species were sampled at the beginning of the grazing season and used as substrates in an in vitro batch fermentation system. After 24h of fermentation, plants affected volatile fatty acids profiles, ammonia yield, and dry matter (DM) digestibilities. Carum carvi, Ranunculus. acris and Festuca rubra showed the highest total production of methane per unit of digested DM while Potentilla erecta was the species that produced less methane. In terms of methane as a percentage of the total gas, F. rubra had the highest value (28.9%) while R. acris had the lowest (24.2%). Total gas and methane production were monitored continuously and the percentage of methane in total gas was fitted with the Gompertz model. Plants differed significantly (p 0.9). The two grasses (F. rubra and Poa alpina) together with Hypericum maculatum showed an opposite behaviour with low values in MFR, A and a longer TMFR. The results of the methane production kinetics allow for an in-depth evaluation of plant species, adding further information to those registered at the end of fermentation
A new equipment for continuous measurement of methane production in a batch in vitro rumen system
Full text linkA 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
A meta-analysis on the relationship between rumen fermentation parameters and protozoa counts in in vitro batch experiments
No full textPresent meta-analysis examines recent in vitro rumen batch experiments where a significant change in the protozoa population was measured after the additions of different substances thought to modify in vitro rumen metabolism. The aim is to study how protozoa number is relating to methane yield and rumen fermentation parameters. Approximately 80 % of the 46 trials from the selected 27 papers (for a total of 201 dietary treatments) tested plant-derived substances, either alone or in mixtures, and 24 trials used rumen fluid from cattle and 22 from sheep. In vitro fermentations with sheep fluid used slightly larger bottles (113 vs 94 mL, P < 0.05), but the inoculum volume, substrate amount, and fermentation duration (38.2 mL, 328.9 mg, and 32.3 h on average, respectively) did not differ (P > 0.05). Only ammonia concentration in cattle fluids was higher compared to sheep (274.2 vs 137.3 mg/L, P < 0.01). Within each trial, we calculated the percentage variation of protozoa compared to control bottles and the majority of the experimental treatments reduced the number of protozoa, by an average of-27.5 %. The relationship between fermentation parameters and variations of pro-tozoa was studied by linear regressions, adjusted for trial effect. In general, protozoa variation in fermentation liquids did not affect total gas production or the sum of volatile fatty acids con-centration. Contrarily, a decrease in protozoa numbers was associated with a significant decrease in methane production, both in absolute terms (R2 = 0.604) and as a proportion of total gas (R2 = 0.528). In terms of individual volatile fatty acids, there was a slight decrease in acetate (R2 = 0.298), an increase in propionate (R2 = 0.388), resulting in a decrease in the acetate: propionate ratio (R2 = 0.379), and no effect of the protozoa on butyrate. Finally, there appeared to be a positive relationship (R2 = 0.580) between protozoa counts and NH3 concentration. In conclusion, rumen protozoa counts of in vitro batch systems are positively associated with methane and ammonia yields, as found in vivo, and this regression study predicts that the com-plete removal of protozoa results in a reduction of about 25 % and 36 % of total ammonia and methane yields, respectively. Batch fermentation systems appear to be appropriate for testing substances that can modulate protozoa counts and related fermentative characteristics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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