2,486 research outputs found
Sampling international migrants with origin-based snowballing method:
No full textThis paper provides a methodological assessment of the advantages and drawbacks of the origin-based snowballing technique as a reliable method to construct representative samples of international migrants in destination areas. Using data from the MAFE-Senegal Project, our results indicate that this is a very risky method in terms of quantitative success. Besides, it implies some clear selection biases: it over-represents migrants more strongly connected to their home country, and it tends to overestimate both poverty in households at origin and the influence of previous migration experiences of social networks on individuals’ out-migration.international migration, sample, survey methodology
Does the complexity of the rumen microbial ecology preclude methane mitigation?
No full textRuminant livestock are responsible for production of a portion of greenhouse gases, particularly methane (61Tg/yr) which is believed to contribute to global warming and climate change. Methane is an end product of fermentation of plant material by the microbial ecosystem in the rumen. Methanogenesis is undertaken by methanogenic archaea and is a mechanism by which H2 is removed from fermentation in order to regenerate biochemical co-factors such as NAD+. The microbial ecosystem is very complex and involves thousands of species of bacteria (1010–1011cells/ml), archaea (107–109cells/ml), protozoa (104–106cells/ml), fungi (103–106cells/ml), and viruses (109–1010cells/ml), which interact with the feed, their host and each other. This ecosystem is relatively poorly understood, particularly inter-species interactions and interactions with the host. Less than 15% of the microbial species in the gastrointestinal tract have been cultured and characterised. However, knowledge of this ecosystem is accumulating, particularly with the advent of molecular biology and culture independent technologies. New high throughput sequencing methodologies, such as pyrosequencing, will greatly improve the rate of knowledge acquisition and techniques such as Stable Isotope Probing will enhance our ability to understand species inter-relationships. While we can expect an increase in our knowledge of this complex ecosystem, and an improved ability to predictably lower CH4 emissions, examples of successful reductions already exist, including use of feeds (e.g., cereal grains) and chemical additives (e.g., 2-bromo-ethane sulfonate, bromochloromethane). Achieving meaningful reductions in CH4 emissions may be possible with advances in our knowledge of the intricacies of this complex ecosystem. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson
Use of fibrolytic enzymes additives to enhance in vitro ruminal fermentation of corn silage
No full textTwo experiments were conducted to evaluate the effect of four enzyme additives on ruminal fermentation of corn silage using a 48 h batch culture in vitro assay with buffer and ruminal fluid. Experiment 1 (Exp. 1) and Experiment 2 (Exp. 2) were conducted as completely randomized designs each with two runs and four replicates. The enzyme additives (E1, E2, E3, and E4) were commercial products that provided a range in endoglucanase, exoglucanase, and xylanase activities. For both xylanase (birch wood and oat spelt substrate) and endoglucanase (carboxymethylcellulose substrate), the enzyme products (per ml) were ranked E4>E1>E2>E3. In Exp. 1, the four enzymes were added at 0, 2, 4, and 8 μl/g of corn silage dry matter (DM), whereas in Exp. 2 enzymes were added at 0, 0.5, 1, 2, and 4 μl/g DM. Gas production (GP) was measured at 3, 6, 12, 18, 24, and 48 h after incubation. Disappearance of DM (DMD), neutral detergent fiber (NDFD), and acid detergent fiber (ADFD), and volatile fatty acid concentrations (VFA; total and individual molar proportions) were determined after 24 and 48 h. In Exp. 1, E1 and E2 had higher NDFD and ADFD at 24 and 48 h of incubation (P0.05) for any of the fermentation variables at either 24 or 48 h of incubation in Exp. 2. There were differences amongst the additives for total VFA at 24 and 48 h (P≤0.05); increasing enzyme dose decreased total VFA after 24 h but increased total VFA at 48 h, such that all doses were higher than the control (P<0.001). Overall, the enzyme additives increased NDFD and ADFD of corn silage in vitro; however, E1 and E2 were more effective than E3 or E4. Responses to increasing dose of enzyme were generally linear or curvilinear, and the optimum dose rate differed amongst the products evaluated. Evaluation of the enzymes at 24 and 48 h generally led to the same ranking of the additives, and the degradation of NDF and ADF was more useful in differentiating the enzymes compared with DM and total GP.Fil: Phakachoed, N.. Suranaree University of Technology; TailandiaFil: Suksombat, W.. Suranaree University of Technology; TailandiaFil: Colombatto, Dario. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Beauchemin, K. A.. Agriculture and Agri-Food Canada; Canad
Search for the SM Higgs boson in the + channel
No full textStandard Model Higgs production in association with or gauge bosons, or with obtains a substantial contribution from events with large missing transverse energy. It is found that the decay channel has a significant discovery potential, with large signal to background ratio, when missing transverse energy of GeV is required. Very good reconstruction of \Esl_T is required, however. A measurement of the rate of this channel should be useful in determining the strength of the Higgs coupling to gauge bosons
A protease additive increases fermentation of alfalfa diets by mixed ruminal microorganisms in vitro
No full textIn vitro experiments were conducted to examine the characteristics and mode of action of a protease that increased the ruminai fiber digestibility of alfalfa hay. A commercial source of protease (Protex 6L, Genencor Int., Rochester, NY), already characterized for its main activities, was further analyzed to determine protease activity in response to pH, molecular size by SDS-PAGE, specificity to degrade model or feed substrates, response to autoclaving, and action of specific protease inhibitors in the absence or presence of ruminai fluid. In addition, batch culture in vitro incubations in buffered ruminal fluid were conducted to compare the enzyme product with purified protease sources, and dose-response studies (0 to 10 μL/g of forage DM) were carried out using alfalfa hay as a substrate. The enzyme product was shown to be an alkaline protease (optimum pH >8.5) of approximately 30 kDa. Specificity in the absence of ruminai fluid showed that the enzyme was active against gelatin and casein to the same extent, whereas it had limited (21% of the total) activity on BSA. In the presence of ruminai fluid and with the use of feed substrates, the protease increased (P < 0.05) 22-h IVDMD (%) of alfalfa hay, fresh corn silage, dry-rolled corn, and a total mixed ration composed of the 3 ingredients (39.5 vs. 44.7; 50.3 vs. 54.5; 63.8 vs. 68.4; and 55.4 vs. 56.4 for control vs. protease for each feed, respectively). Inhibitor studies in the absence of ruminai fluid indicated that the enzyme was inhibited most by a serine protease inhibitor but not by cysteineor metalloprotease inhibitors (10 vs. 1.9 and 0.1%, respectively). In the presence of ruminal fluid, the serine protease inhibitor reversed (P < 0.05) the increase in alfalfa IVDMD achieved by the enzyme product, such that IVDMD was similar to that of the control treatment. Comparisons among different proteases revealed that only pure subtilisin achieved increases in IVDMD that were similar to those with protease, suggesting the serine protease was subtilisin-like (EC 3.4.1.62). Dose-response studies using alfalfa hay as substraje showed quadratic responses in IVDMD, NDF digestion, and hemicellulose and protein disappearance. It is postulated that this enzyme acts by removing structural proteins in the cell wall, allowing ruminal microbes to gain faster access to digestible substrates.Fil: Colombatto, Dario. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Beauchemin, K. A.. Agriculture Et Agroalimentaire Canada; Canad
Test of CP invariance in Higgs boson vector-boson-fusion production using the H → γγ channel with the ATLAS detector
No full textA test of
C
P
invariance in Higgs boson production via vector-boson fusion has been performed in the
H
→
γ
γ
channel using
139
fb
−
1
of proton-proton collision data at
√
s
=
13
TeV
collected by the ATLAS detector at the LHC. The optimal observable method is used to probe the
C
P
structure of interactions between the Higgs boson and electroweak gauge bosons, as described by an effective field theory. No sign of
C
P
violation is observed in the data. Constraints are set on the parameters describing the strength of the
C
P
-odd component in the coupling between the Higgs boson and the electroweak gauge bosons in two effective field theory bases:
˜
d
in the HISZ basis and
c
H
˜
W
in the Warsaw basis. The results presented are the most stringent constraints on
C
P
violation in the coupling between Higgs and weak bosons. The 95% C.L. constraint on
˜
d
is derived for the first time and the 95% C.L. constraint on
c
H
˜
W
has been improved by a factor of 5 compared to the previous measurement
The effect of enzyme treatment on the in vitro fermentation of Lucerne incubated with equine faecal inocula
No full textA series of experiments was conducted to determine the effects of a fibrolytic enzyme preparation (enzyme 1; E1) on the in vitro fermentation of lucerne incubated with equine faecal inocula. In experiment 1, high-temperature-dried (HT) lucerne was treated with five levels of E1 (0 to 2.4 ml/g DM) and incubated at 50 degrees C for 20 h. Samples then received a simulated foregut digestion (SFD) treatment before DM and NSP analysis. In experiment 2, HT lucerne was treated with the same enzyme levels used in experiment 1. Samples were then split into two groups; plus or minus an SFD treatment before in vitro fermentation using an equine faecal inoculum. In experiment 3, fresh and wilted lucerne were treated with the same levels of E1 as experiments 1 and 2, incubated at 50 degrees C for 20 h, then fermented in vitro. For experiment 4, fresh and wilted lucerne were treated with low levels (0 to 0.008 ml/g DM) of E1 before fermentation. E1 significantly (P<0.05) enhanced DM and NSP losses from HT lucerne following SFD treatment compared with the control. High levels of E1 significantly (P<0.05) enhanced the rate, but not extent, of fermentation of HT, wilted and fresh lucerne; however, low levels of E1 were ineffective. At higher application levels, E1 appears to have considerable potential to enhance the nutritive value of lucerne for horses. Information on the fermentation kinetics of the substrates was valuable; all end-point measurements showed no effect of enzyme treatment
The effect of dietary adaptation on the susceptibility to and recovery from ruminal acidosis in beef cattle
No full textFeeding diets rich in rapidly fermentable non-structural carbohydrates can lead to the development of ruminal acidosis. This study was conducted to determine if the duration of time that cattle are fed a high-grain diet affects their absorption of short-chain fatty acids (SCFA) and susceptibility to, and recovery from, ruminal acidosis. Sixteen Angus heifers (BW ± SEM, 261 ± 6.1 kg) were assigned to 1 of 4 blocks, and fed a backgrounding diet consisting of 60% barley silage, 30% barley grain, and 10% supplement (DM basis). Within block, cattle were randomly assigned to 1 of 2 treatments differing in the number of days they were fed the high-grain diet prior to an acidosis challenge: 34 d for long-adapted (LA) and 8 d for short-adapted (SA). All cattle were exposed to the same 20-d dietary transition using 5 dietary steps until achieving the final diet that contained 9% barley silage, 81% barley grain, and 10% supplement (DM basis). Data were collected during an 8-d baseline period (BASE), on the d of the acidosis challenge (CHAL), and during two consecutive 8 d recovery periods (REC1 and REC2). Ruminal acidosis was induced by restricting feed to 50% of DMI:BW for 24 h followed by an intraruminal infusion of ground barley at 10% DMI:BW. Cows were then given their regular diet allocation 1 h after the intraruminal infusion. The duration of time fed the high-grain diet did not affect ruminal pH, lactate, or SCFA concentrations (P > 0.050). However, during BASE and on the day of CHAL the SA heifers experienced greater linear (P = 0.031), quadratic (P = 0.016), and cubic (P = 0.008) between day change in the duration of time that pH was < 5.5 than LA heifers. Relative to BASE, inducing acidosis increased daily duration (531 to 1020 min/d; P < 0.001) and area (176 to 595 (min × pH)/d; P < 0.001) that pH was < 5.5. Inducing ruminal acidosis also increased the daily mean (0.3 to 11.4 mM; P = 0.013) and maximum (1.3 to 29.3 mM; P = 0.008) rumen fluid lactate concentrations relative to BASE, suggesting that an acute bout of ruminal acidosis was induced. In addition, a treatment × day interaction for the duration that pH was < 5.5 during REC1 suggests that LA cattle tended to recover from the CHAL more rapidly than SA cattle (P = 0.085). Indeed, analysis of covariance confirmed that the LA heifers experienced a quicker linear (P = 0.019) recovery over time from CHAL. The greater rate of recovery possibly resulted from the LA heifers having greater rates of both fractional butyrate (45 vs. 36 %/h; P = 0.019) and propionate absorption (42 vs. 34 %/h; P = 0.045), and tending to have greater rates, on an absolute basis, of butyrate absorption (94 vs. 79 mmol/h; P = 0.087)
iii
and, on a fractional basis, of total SCFA absorption (37 vs. 32 %/h; P = 0.100). Treatment × period interactions revealed that LA heifers had greater serum D-lactate concentrations (P = 0.003), and fractional rates of lactate absorption (P = 0.024) than SA heifers, during CHAL and REC1, respectively. When treatments were pooled, the absorption (%/h and mmol/h) of acetate, propionate, butyrate, and total SCFA increased between REC1 and REC2, with intermediate values for BASE (P ≤ 0.05). Corresponding to a reduction in absorption during REC1 (2 d post CHAL), saliva production (kg/h; P = 0.018) increased between BASE and REC1, with intermediate values for REC2. These results indicate that the duration of time cattle are fed a high-grain diet may stabilize rumen pH, both prior to and after an induced bout of acute ruminal acidosis, likely through increased ruminal absorptive capacity for SCFA and lactate. In addition, this study found evidence to suggest that beef cattle possess the ability to increase saliva secretion in order to compensate for decreased absorptive capacity
ATLAS measurements of jets and heavy flavor produced in association with W and Z bosons
No full textThe production of jets and/or heavy flavours in association with a W or Z boson represents an important process with which to study QCD in a multi-scale environment. Unprecedented precision is achieved in measurements of differential cross sections and multiplicities, and comparisons are made to state-of-the-art high NLO QCD calculations of high-multiplicity final states. Jets containing b- or c-hadrons are also identified, and correlations are studied
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