38 research outputs found
Impact of mash feeding versus pellets on propionic/butyric acid levels and on total Escherichia coli load in the gastrointestinal tract of growing pigs
Feed characteristics may influence
the bacterial community composition and metabolic
activities in the pig gastrointestinal tract, known to be
associated with positive effects on the gut. Use of mash
feed is associated with reduced Salmonella excretion,
but little is known of its effect on the Escherichia coli
population or of the mechanism of action. Our objectives
were to assess the effect of feed texture combined
with feed particle size on VFA profiles and levels,
total E. coli count, and the presence of genes encoding
virulence factors of pathogenic E. coli strains in the
digestive tract along with their impact on pig performance
of fattening pigs. Pigs (n = 840) on a commercial
farm received mash or pellet diets of different particle
sizes during the fattening period. Caecal and colon contents
from 164 pigs were sampled at the slaughterhouse
for enumeration of E. coli by quantitative PCR (qPCR)
and for VFA quantification by capillary gas chromatography.
The yccT gene was used to enumerate total E.
coli. Improved pig performances associated with pellet
texture and a 500-ÎĽm size were observed. Caecal (P =
0.02) and colon (P < 0.01) propionic acid concentrations
were lower for pigs receiving pellet rather than
mash feed. Similarly, caecal (P = 0.01) and colon (P <
0.001) butyric acid concentrations were also lower for
pigs receiving pellet rather than mash feed, as determined
by capillary gas chromatography. Moreover,
caecal (P = 0.03) and colon (P < 0.001) butyric acid
concentrations were higher for pigs receiving a feed
with a 1,250-ÎĽm particle size rather than a 500-ÎĽm
particle size. On the other hand, total caecal and colon
E. coli levels were higher for pigs receiving pellet feed
than for those receiving mash feed. For total E. coli
enumeration, caecal (P < 0.01) and colon (P < 0.01)
yccT gene copies were higher for pigs receiving pellet
rather than mash feed. No effect of particle size on
fatty acid concentrations or on E. coli numbers was
observed. Virulence gene quantification revealed no
trend. Taken together, results showed that mash feed
is associated with lower growth performance but with
favorable intestinal changes linked to VFA levels and E.
coli reduction in the intestine
Variabilidade espacial da comunidade bacteriana intestinal de suĂnos suplementados com antibiĂłticos ou extratos herbais
Precisão da tira reagente e do exame microscópico da urina no diagnóstico de infecções do trato urinário em porcas
CaracterĂsticas e frequĂŞncia das doenças de suĂnos na RegiĂŁo Central do Rio Grande do Sul
A reverse transcription-polymerase chain reaction method to analyze porcine cytokine gene expression
International audienc
Atomic radical abatement of organic impurities from electron beam deposited metallic structures
Focused electron beam induced processing (FEBIP) of volatile organometallic precursors has become an effective and versatile method of fabricating metal-containing nanostructures. However, the electron stimulated decomposition process responsible for the growth of these nanostructures traps much of the organic content from the precursor’s ligand architecture, resulting in deposits composed of metal atoms embedded in an organic matrix. To improve the metallic properties of FEBIP structures, the metal content must be improved. Toward this goal, the authors have studied the effect of atomic hydrogen (AH) and atomic oxygen (AO) on gold-containing deposits formed from the electron stimulated decomposition of the FEBIP precursor, dimethyl-(acetylacetonate) gold(III), AuIII(acac)Me2. The effect of AH and AO on nanometer thick gold-containing deposits was probed at room temperature using a combination of x-ray photoelectron spectroscopy (XPS), scanning Auger electron spectroscopy, and atomic force microscopy (AFM). XPS revealed that deposits formed by electron irradiation of AuIII(acac)Me2 are only ?10% gold, with ?80% carbon and ?10% oxygen. By exposing deposits to AH, all of the oxygen atoms and the majority of the carbon atoms were removed, ultimately producing a deposit composed of ?75% gold and ?25% carbon. In contrast, all of the carbon could be etched by exposing deposits to AO, although some gold atoms were also oxidized. However, oxygen was rapidly removed from these gold oxide species by subsequent exposure to AH, leaving behind purely metallic gold. AFM analysis revealed that during purification, removal of the organic contaminants was accompanied by a decrease in particle size, consistent with the idea that the radical treatment of the electron beam deposits produced close packed, gold particles. The results suggest that pure metallic structures can be formed by exposing metal-containing FEBIP deposits to a sequence of AO followed by AH.IST/Imaging Science and TechnologyApplied Science
Electron induced dissociation of trimethyl (methylcyclopentadienyl) platinum (IV): Total cross section as a function of incident electron energy
The total cross section has been measured for the electron induced dissociation of trimethyl (methylcyclopentadienyl) platinum (IV) [MeCpPt(IV)Me3], a Pt precursor often used in focused electron beam induced processing (FEBIP), for incident electron energies ranging between 3–3 keV. Measurements were performed for the precursor in the adsorbed state under ultrahigh vacuum conditions. The techniques used in this study were temperature programmed desorption, x-ray photoelectron spectroscopy and mass spectrometry. Two surfaces were used in these experiments, amorphous carbon overlayers containing embedded Pt atoms (a:C-Pt), formed by the electron decomposition of the Pt precursor, and atomically clean Au. The results from these three experiments revealed a comparatively low total cross section at 8 eV (4.2+/-0.3xE?17 cm2 on the a:C-Pt and 1.4+/-0.1xE?17 cm2 on the Au) that increases with increasing incident electron energy, reaching a maximum at around 150 eV (4.1+/-0.5xE?16 cm2 on the a:C-Pt and 2.3+/-0.2xE?16 cm2 on the clean Au), before decreasing at higher incident electron energies, up to 3000 eV. Differences in the measured cross sections between Au and a:C-Pt surfaces demonstrate that the substrate can influence the reaction cross section of adsorbed species. Temperature programmed desorption was also used to measure the adsorption energy of MeCpPt(IV)Me3, which was found to depend on both the substrate and the adsorbate coverage. The work in this paper demonstrates that surface science techniques can be used to quantitatively determine the total cross section of adsorbed FEBIP precursors for electron induced dissociation as a function of incident electron energy. These total cross section values are necessary to obtain quantitatively accurate information from FEBIP models and to compare the reaction efficiencies of different precursors on a quantitative basis. (doi:10.1063/1.3225091)ISTApplied Science
Comparison of necrotoxigenic Escherichia coli isolates from farm animals and from humans
34 ref.International audienc