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      Efecto modulador de Leucaena leucocephala sobre la microbiota ruminal Translated title: Modulator effect of Leucaena leucocephala on the rumen microbiota


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          Con el objetivo de evaluar el efecto modulador de Leucaena leucocephala en la población de bacterias metanogénicas y otros grupos microbianos del rumen, se condujo un experimento bajo un diseño completamente aleatorizado en arreglo factorial (4 x 4, cuatro proporciones de leucaena y cuatro tiempos de fermentación) en condiciones in vitro. Los tratamientos consistieron en cuatro relaciones de pasto estrella (Cynodon nlenfuensis) con leucaena, los cuales fueron: Tratamiento A=100:0, B=80:20, C=75:25 y D=70:30. Los muestreos se efectuaron antes de incubar (hora 0), a las 4, 8 y 12 h, después de iniciada la fermentación. Los conteos de bacterias metanogénicas fueron 40,22 38,42 13,98 y 12,46 x 107 ufc/mL para los tratamientos A, B, C y D, respectivamente. El modulador incrementó la población de bacterias celulolíticas en relación al tratamiento control sin suplementar y la mejor respuesta se encontró con las relaciones 80:20 y 70:30. Las poblaciones de hongos celulolíticos fueron 2,08 3,49 3,69 y 4,48 x 105 uft/mL para los tratamientos A, B. C y D, respectivamente. La población de protozoarios estuvo entre 1,50 a 2,75 x 105 células/mL bajo las condiciones experimentales desarrolladas. En todos los tratamientos con L. leucocephala, las poblaciones fueron significativamente más bajas, observándose la menor población para la relación 80:20. Se concluye que Leucaena leucocephala al 25% de la dieta es adecuada para reducir la población de bacterias metanogénicas ruminales sin comprometer la población total de bacterias celulolíticas.

          Translated abstract

          With the objective to evaluate the modulator effect of Leucaena leucocephala on the methanogenic bacteria and other microbial groups in the rumen was conducted a trial according to a completely randomized design in a factorial arrangement (4 x 4, four leucaena proportions and four times of fermentation), under in vitro conditions. The trial consisted of four star grass (Cynodon nlemfuensis) with leucaena ratios, which were: treatment A=100:0, B=80:20, C=75:25, and D=70:30. The sampling was performed before the incubation (0 hour), and at 4, 8, and 12 h of fermentation. The counts of methanogenic bacteria were 40.22, 38.42, 13.98, and 12.46 x 107 cfu/mL for the treatments A, B, C, and D, respectively. The modulator increased the population of cellulolytic bacteria, compared with the control without supplement, and the best response was found in the ratios 80:20 and 70:30. The populations of cellulolytic fungi were 2.08, 3.49, 3.69, and 4.48 x 103 tfu/mL for A, B, C, and D treatments, respectively. The protoozoa population varied from 1.50 to 2.75 x 105 cell/mL, under the trial conditions. In all cases with L. leucocephala as modulator the populations were significantly small, but the smallest was found when the ratio 80:20 of star grass:modulator was used. It is concluded that the modulator from the fermentation with L. leucocephala is suitable for reducing the population of rumen methanogenic bacteria without affecting the total population of cellulolytic bacteria.

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            Methane emissions from feedlot cattle fed barley or corn diets.

            Methane emitted from the livestock sector contributes to greenhouse gas emissions worldwide. Understanding the variability in enteric methane production related to diet is essential to decreasing uncertainty in greenhouse gas emission inventories and to identifying viable greenhouse gas reduction strategies. Our study focused on measuring methane in growing beef cattle fed corn- or barley-based diets typical of those fed to cattle in North American feedlots. The experiment was designed as a randomized complete block (group) design with two treatments, barley and corn. Angus heifer calves (initial BW = 328 kg) were allocated to two groups (eight per group), with four cattle in each group fed a corn or barley diet. The experiment was conducted over a 42-d backgrounding phase, a 35-d transition phase and a 32-d finishing phase. Backgrounding diets consisted of 70% barley silage or corn silage and 30% concentrate containing steam-rolled barley or dry-rolled corn (DM basis). Finishing diets consisted of 9% barley silage and 91% concentrate containing barley or corn (DM basis). All diets contained monensin (33 mg/kg of DM). Cattle were placed into four large environmental chambers (two heifers per chamber) during each phase to measure enteric methane production for 3 d. During the backgrounding phase, DMI was greater by cattle fed corn than for those fed barley (10.2 vs. 7.6 kg/d, P < 0.01), but during the finishing phase, DMI was similar for both diets (8.3 kg/d). The DMI was decreased to 6.3 kg/d with no effect of diet or phase while the cattle were in the chambers; thus, methane emissions (g/d) reported may underestimate those of the feedlot industry. Methane emissions per kilogram of DMI and as a percentage of GE intake were not affected by grain source during the backgrounding phase (24.6 g/kg of DMI; 7.42% of GE), but were less (P < 0.05) for corn than for barley during the finishing phase (9.2 vs. 13.1 g/kg of DMI; 2.81 vs. 4.03% of GE). The results indicate the need to implement dietary strategies to decrease methane emissions of cattle fed high-forage backgrounding diets and barley-based finishing diets. Mitigating methane losses from cattle will have long-term environmental benefits by decreasing agriculture's contribution to greenhouse gas emissions.
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              Effect of select nitrocompounds on ruminal fermentation; an initial look at their potential to reduce economic and environmental costs associated with ruminal methanogenesis.

              Methane production by ruminal microbes during the digestion of feedstuffs is an inefficient process resulting in losses of 2-12% of the gross energy consumed by ruminants. Presently, we report the effect of three inhibitors on ruminal methane production in vitro. Mixed populations of ruminal microbes collected from cannulated cows maintained on an alfalfa hay:corn diet (50:50) were incubated at 39 degrees C for 24 h under a 100% carbon dioxide gas phase in closed tubes with 72 mM added sodium formate. Cultures were supplemented with 12 mM 2-nitropropanol, nitroethane or nitroethanol (experiment 1) or with 2, 12 or 24 mM nitroethane or a combination of 12 mM nitroethane and 4 mM nitroethanol (experiment 2). Control cultures containing no added nitrocompound were incubated simultaneously with treated incubations. Methane concentrations were reduced (P<0.05) from those measured in control incubations (27.6 +/- 2.1 and 17.7 +/- 0.8 micromol/ml; mean +/- SD for experiments 1 and 2, respectively) by at least 57% and as much as 94% in the nitrocompound supplemented incubations. By comparison, the widely fed methane inhibitor, monensin, typically reduces ruminal methane production by about 33%. Concentrations of volatile fatty acids and ammonia that accumulated in the nitrocompound supplemented incubations were not markedly affected compared to those produced by control cultures despite the reductions in methane produced. Hydrogen accumulated only slightly in cultures supplemented with the nitrocompounds. These results demonstrate that 2-nitropropanol, nitroethane and nitroethanol inhibit ruminal methane production. Further research is warranted to determine the mechanisms responsible for this inhibition and to see if these inhibitors can be used in practical application to reduce economic and environmental costs associated with ruminal methanogenesis.

                Author and article information

                Zootecnia Tropical
                Zootecnia Trop.
                Instituto Nacional de Investigaciones Agricolas INIA, Maracay, Venezuela. (Maracay, Aragua, Venezuela )
                September 2008
                : 26
                : 3
                : 249-252
                [01] La Habana orgnameInstituto de Ciencia Animal Cuba
                S0798-72692008000300019 S0798-7269(08)02600319


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                Artículos Científicos

                rumen,metanógenos bacterias celulolíticas,hongos,modulador,methanogenic,cellulolytic bacteria,fungi,modulator


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