546 research outputs found

    Stellar Mass to Halo Mass Scaling Relation for X-ray Selected Low Mass Galaxy Clusters and Groups out to Redshift z1z\approx1

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    We present the stellar mass-halo mass scaling relation for 46 X-ray selected low-mass clusters or groups detected in the XMM-BCS survey with masses 2×1013MM5002.5×1014M2\times10^{13}M_{\odot}\lesssim M_{500}\lesssim2.5\times10^{14}M_{\odot} at redshift 0.1z1.020.1\le z \le1.02. The cluster binding masses M500M_{500} are inferred from the measured X-ray luminosities \Lx, while the stellar masses MM_{\star} of the galaxy populations are estimated using near-infrared imaging from the SSDF survey and optical imaging from the BCS survey. With the measured \Lx\ and stellar mass MM_{\star}, we determine the best fit stellar mass-halo mass relation, accounting for selection effects, measurement uncertainties and the intrinsic scatter in the scaling relation. The resulting mass trend is MM5000.69±0.15M_{\star}\propto M_{500}^{0.69\pm0.15}, the intrinsic (log-normal) scatter is σlnMM500=0.360.06+0.07\sigma_{\ln M_{\star}|M_{500}}=0.36^{+0.07}_{-0.06}, and there is no significant redshift trend M(1+z)0.04±0.47M_{\star}\propto (1+z)^{-0.04\pm0.47}, although the uncertainties are still large. We also examine MM_{\star} within a fixed projected radius of 0.50.5~Mpc, showing that it provides a cluster binding mass proxy with intrinsic scatter of 93%\approx93\% (1σ\sigma in M500M_{500}). We compare our M=M(M500,z)M_{\star}=M_{\star}(M_{500}, z) scaling relation from the XMM-BCS clusters with samples of massive, SZE-selected clusters (M5006×1014MM_{500}\approx6\times10^{14}M_{\odot}) and low mass NIR-selected clusters (M5001014MM_{500}\approx10^{14}M_{\odot}) at redshift 0.6z1.30.6\lesssim z \lesssim1.3. After correcting for the known mass measurement systematics in the compared samples, we find that the scaling relation is in good agreement with the high redshift samples, suggesting that for both groups and clusters the stellar content of the galaxy populations within R500R_{500} depends strongly on mass but only weakly on redshift out to z1z\approx1.Comment: 15 pages, 10 figures. Accepted for publication in MNRA

    Comparison of fermentation characteristics and bacterial diversity in the rumen of sheep and batch cultures of rumen microorganisms

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    The objective of the current study was to assess how closely batch cultures (BC) of rumen microorganisms can mimic the dietary differences in fermentation characteristics found in the rumen, and to analyse changes in bacterial diversity over the in vitro incubation period. Four ruminally and duodenally cannulated sheep were fed four diets having forage : concentrate ratios (FCR) of 70 : 30 or 30 : 70, with either alfalfa hay or grass hay as forage. Rumen fluid from each sheep was used to inoculate BC containing the same diet fed to the donor sheep, and the main rumen fermentation parameters were determined after 24 h of incubation. There were differences between BC and sheep in the magnitude of most measured parameters, but BC detected differences among diets due to forage type similar to those found in sheep. In contrast, BC did not reproduce the dietary differences due to FCR found in sheep for pH, degradability of neutral detergent fibre and total volatile fatty acid (VFA) concentrations. There were differences between systems in the magnitude of most determined parameters and BC showed higher pH values and NH3–N concentrations, but lower fibre degradability and VFA and lactate concentrations compared with sheep. There were significant relationships between in vivo and in vitro values for molar proportions of acetate, propionate and butyrate, and the acetate : propionate ratio. The automated ribosomal intergenic spacer analysis (ARISA) of 16S ribosomal deoxyribonucleic acid showed that FCR had no effect on bacterial diversity either in the sheep rumen fluid used as inoculum (IN) or in BC samples. In contrast, bacterial diversity was greater with alfalfa hay diets than those with grass hay in the IN, but was unaffected by forage type in the BC. Similarity index between the bacterial communities in the inocula and those in the BC ranged from 67·2 to 74·7%, and was unaffected by diet characteristics. Bacterial diversity was lower in BC than in the inocula with 14 peaks out of a total of 181 detected in the ARISA electropherograms never appearing in BC samples, which suggests that incubation conditions in the BC may have caused a selection of some bacterial strains. However, each BC sample showed the highest similarity index with its corresponding rumen IN, which highlights the importance of using rumen fluid from donors fed a diet similar to that being incubated in BC when conducting in vitro experiments

    Estudio comparativo entre el cultivo convencional y ecológico de trigo para alimentación animal

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    El objetivo de este estudio fue investigar las diferencias en el rendimiento productivo y el valor nutritivo entre el cultivo ecológico y convencional de trigo invernal para su utilización en alimentación animal. La producción de forraje fue determinada en el mes de mayo de tres años consecutivos y la producción de paja y grano se determinó en el mes de julio de los dos primeros años. Las muestras fueron secadas para determinar su composición química y su digestibilidad in vitro. Adicionalmente, 500 mg de cada muestra fueron incubados con 50 mL de líquido ruminal tamponado a 39°C. En estas incubaciones se midió la producción de gas a diferentes tiempos para estimar la cinética de fermentación y se analizaron los parámetros de fermentación tras 24 horas de incubación. La producción de forraje, grano y paja fue mayor en las parcelas convencionales que en las ecológicas. El contenido en proteína bruta fue más bajo en el cultivo ecológico que en el convencional, tanto para el forraje como para el grano. La digestibilidad in vitro fue similar para los dos tipos de cultivo y no existieron diferencias en la cinética de degradación ni en la producción de ácidos grasos volátiles. Los resultados indican que el cultivo ecológico provocó una disminución de la producción y en el contenido de proteína en el forraje y en los granos de trigo, pero no se observaron efectos en la degradación ruminal. Estos resultados indican que el sistema de cultivo del trigo afecta a su composición química y por ello debe realizarse una valoración previa del mismo cuando se utilice para alimentación animal.The objective of this study was to assess the differences in yield and nutritive value of organically and conventionally grown wheat crops as animal feeds. Forage yield was determined in May in three consecutive years and straw and grain yield was determined in July in the two first years. Samples were dried to determine their chemical composition and in vitro digestibility. Additionally, 500 mg of each sample were incubated with 50 mL of buffered rumen fluid at 39°C to estimate rumen fermentation kinetics and fermentation parameters after 24 hours. Forage, grain and straw yield was greater in conventionally grown crops than in organic ones. Crude protein content was lower in organically grown wheat, both for the forage or the grain. In vitro digestibility was similar in both types of cultures and there were no differences in degradation kinetics parameters or volatile fatty acids production. Results indicate that organic cultivation lead to a decrease in yield and crude protein content in forage and wheat grain, but there were no differences in their ruminal degradation. These results indicate that cultivation system affects chemical composition of wheat and, therefore, it is necessary to assess the nutritive value of organically grown cereals intended for animal feeding

    Influence of processing method of rumen contents on microbial populations in the inoculum and in vitro fermentation of substrates of variable composition

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    The in vitro batch culture technique is being increasingly used to study rumen fermentation, but the results are affected by several factors, being the source of the inoculum one of the most relevant. This work was conducted to assess the effects of different processing methods of ruminal contents on microbial populations in the obtained fluid, and its influence on fermentation parameters when the fluid was used as inoculum for in vitro incubations. Rumen contents were obtained from four rumen-fistulated sheep fed a 2:1 alfalfa hay:concentrate diet and subjected to the following treatments: SQ: squeezed through four layers of cheesecloth; FL: SQ treatment and further filtration through a 100-μm nylon cloth; STO: blended for three min at 230 rev min−1 in a Stomacher® and further filtrations as in SQ. Microbial populations’ abundance and bacterial diversity in the ruminal fluids were analysed by quantitative PCR (qPCR) and automated ribosomal intergenic spacer analysis (ARISA), respectively. Three forages (alfalfa hay, grass hay and barley straw) were incubated in vitro, either alone or mixed with concentrate (1:1), using each of the ruminal fluids as inoculum. There were no differences between SQ and FL methods in any of the microbial populations analysed, but STO increased the relative abundance of Fibrobacter succinogenes and Ruminococcus albus (P 0.05) by the processing methods. There were no interactions (P > 0.05) between the processing method and the characteristics of the substrates for any of the fermentation parameters analysed. Compared with SQ, the STO method resulted in greater (P < 0.05) methane production and ammonia-N concentrations in 8 h incubations. After 24 h of incubation, the use of STO inoculum increased (P < 0.05) methane production and dry matter degradability compared with SQ, with no differences in the rest of the parameters. No differences between SQ and FL methods were detected in any parameter. The results show that stomaching the rumen contents prior to inoculation of in vitro cultures modified some microbial populations, but had only subtle effects on fermentation parameters

    Perspectivas y retos de los extractos vegetales como aditivos alimentarios en rumiantes

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    Algunas plantas producen y almacenan compuestos secundarios que ejercen actividades beneficiosas en el organismo humano y animal. En lo que se refiere a su uso en alimentación animal, constituyen una alternativa natural a los aditivos antibióticos promotores del crecimiento, cuyo uso en rumiantes se ha centrado fundamentalmente en sus efectos sobre la fermentación rumial

    Presente y perspectivas de futuro en la UE del empleo de probióticos en la alimentación de rumiantes

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    En este artículo se describe, en primer lugar, la situación legal actual de los probióticos como aditivos en la alimentación de los animales rumiantes en la Unión Europea (UE). A continuación se repasan sus mecanismos de acción, considerando especialmente los últimos avances científicos en referencia a sus acciones sobre las poblaciones microbianas ruminales, y se analizan los factores que influyen en la respuesta de los animales a la administración de estos aditivos. Finalmente, se detallan brevemente las perspectivas de futuro de los probióticos en el ámbito de la ganadería de rumiantes europea

    Evolución temporal de las comunidades microbianas ruminales y los parámetros fermentativos en fermentadores Rusitec

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    Los fermentadores Rusitec (Czerkawski y Breckenridge, 1977) son uno de los tipos de fermentadores más ampliamente utilizados para simular in vitro la fermentación ruminal y permiten realizar estudios de larga duración (semanas). Sin embargo, debido a la prolongada extensión en el tiempo de este tipo de estudios se producen cambios cuantitativos y cualitativos en las poblaciones de microorganismos. Existen algunos estudios que han puesto de manifiesto la disminución de la población de protozoos a lo largo del período de incubación (Carro et al., 1995; Martínez et al., 2011), pero no existe información sobre otras poblaciones microbianas, a pesar de que uno de los requisitos que deberían cumplir los sistemas in vitro es mantener poblaciones microbianas representativas de las existentes en el rumen de los animales. Por ello, el objetivo del presente trabajo fue estudiar la evolución en el tiempo de la abundancia de bacterias, hongos, protozoos y arqueas, así como de los parámetros ruminales en fermentadores Rusitec

    Utilización de enzimas fibrolíticas para mejorar la digestión de forrajes tropicales. I. Influencia del método de aplciacion en la producción de gas in vitro y la composición química

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    Los forrajes tropicales presentan, en general, un menor valor nutritivo que los forrajes de zonas templadas. Sin embargo, su disponibilidad suele ser elevada y en numerosas ocasiones son el único recurso alimenticio disponible para los animales rumiantes. Esta situación limita la productividad de estos animales y por ello se han investigado diferentes estrategias para aumentar el valor nutritivo de los forrajes tropicales. Una de las metodologías propuestas para incrementar la utilización digestiva de los forrajes es el tratamiento de los mismos con enzimas fibrolíticas (Carro y Ranilla, 2001), pero todavía son escasos los estudios realizados con forrajes tropicales. El objetivo de este trabajo fue evaluar el efecto de tres preparados enzimáticos en la fermentación ruminal in vitro y la degradabilidad de tres forrajes tropicales

    The influence of diet on the effectiveness of garlic oil and cinnamaldehyde to manipulate in vitro ruminal fermentation and methane production.

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    The objective of this study was to evaluate the effects of increasing doses [0 (control: CON), 20, 60, 180 and 540 mg/L incubation medium] of garlic oil (GO) and cinnamaldehyde (CIN) on in vitro ruminal fermentation of two diets. Batch cultures of mixed ruminal microorganisms were inoculated with ruminal fluid from four sheep fed a medium-concentrate diet (MC; 50 : 50 alfalfa hay : concentrate) or four sheep fed a high-concentrate diet (HC; 15 : 85 barley straw : concentrate). Diets MC and HC were representative of those fed to dairy and fattening ruminants, respectively. Samples of each diet were used as incubation substrates for the corresponding inoculum, and the incubation was repeated on 4 different days (four replicates per experimental treatment). There were GO × diet-type and CIN × diet-type interactions (P 0.05) total volatile fatty acid (VFA) production at any dose. For MC diet, GO at 60, 180 and 540 mg/L decreased (P 0.05) on butyrate proportion were detected. Methane/VFA ratio was reduced (P < 0.05) by GO at 60, 180 and 540 mg/L for MC diet (0.23, 0.16 and 0.10 mol/mol, respectively), and by GO at 20, 60, 180 and 540 mg/L for HC diet (0.19, 0.19, 0.16 and 0.08 mol/mol, respectively), compared with CON (0.26 and 0.21 mol/mol for MC and HC diets, respectively). No effects (P = 0.16–0.85) of GO on final pH and concentrations of NH3-N and lactate were detected. For both diet types, the highest CIN dose decreased (P < 0.05) production of total VFA, gas and methane, which would indicate an inhibition of fermentation. Compared with CON, CIN at 180 mg/L increased (P < 0.05) acetate proportion for the MC (629 and 644 mmol/mol total VFA for CON and CIN, respectively) and HC (525 and 540 mmol/mol total VFA, respectively) diets, without affecting the proportions of any other VFA or total VFA production. Whereas for MC diet CIN at 60 and 180 mg/L decreased (P < 0.05) NH3-N concentrations compared with CON, only a trend (P < 0.10) was observed for CIN at 180 mg/L with the HC diet. Supplementation of CIN up to 180 mg/L did not affect (P = 0.18–0.99) lactate concentrations and production of gas and methane for any diet. The results show that effectiveness of GO and CIN to modify ruminal fermentation may depend on diet type, which would have practical implications if they are confirmed in vivo

    Utilización de enzimas fibrolíticas para mejorar la digestión de forrajes tropicales. II. Efectos en la fermetación ruminal in vitro y la degradabilidad

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    En muchos países tropicales los sistemas productivos de animales rumiantes se basan en una amplia utilización de recursos forrajeros. Sin embargo, estos recursos suelen tener una baja calidad, por lo que cualquier mejora de su valor nutritivo tendrá una repercusión positiva en la productividad de los animales. En los últimos años se han realizado numerosos estudios para evaluar diferentes enzimas fibrolíticas como aditivos para mejorar el valor nutritivo de forrajes, pero la mayoría de ellos han utilizado forrajes de elevada calidad y apenas existen estudios con forrajes de baja calidad. Por otra parte, los resultados han sido muy variables, ya que la efectividad de las enzimas se ve afectada por numerosos factores, siendo el tipo de forraje y el método de aplicación de las enzimas dos de los más importantes (Giraldo et al., 2008). El objetivo del presente estudio fue evaluar el efecto de tres enzimas fibrolíticas exógenas en la fermentación ruminal in vitro de tres forrajes tropicales cuando las enzimas se aplicaron 24 h antes o en el momento de la incubación
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