RESUMO

Ameliorating methane (CH4) emissions from ruminants would have environmental benefits, but it is necessary to redirect metabolic hydrogen ([H]) toward useful sinks to also benefit animal productivity. We hypothesized that inhibiting rumen methanogenesis would increase de novo synthesis of microbial amino acids (AA) as an alternative [H] sink if sufficient energy and carbon are provided. We examined the effects of inhibiting methanogenesis with 9, 10-anthraquione (AQ) on mixed rumen batch cultures growing on cellulose or starch as sources of energy and carbon contrasting in fermentability, with ammonium (NH4+) or trypticase (Try) as nitrogen (N) sources. Inhibiting methanogenesis with AQ inhibited digestion with cellulose but not with starch, and decreased propionate and increased butyrate molar percentages with both substrates. Inhibiting methanogenesis with 9, 10-anthraquinone increased de novo synthesis of microbial AA with starch but not with cellulose. The decrease in the recovery of [H] caused by the inhibition of methanogenesis was more moderate with starch due to an enhancement of butyrate and AA as [H] sinks. There may be an opportunity to simultaneously decrease the emissions of CH4 and N with some ruminant diets and replace plant protein supplements with less expensive non-protein nitrogen sources such as urea.

RESUMO

There is an interest in controlling rumen methanogenesis as an opportunity to both decrease the emissions of greenhouse gases and improve the energy efficiency of rumen fermentation. However, the effects of inhibiting rumen methanogenesis on fermentation are incompletely understood even in in vitro rumen cultures, as the recovery of metabolic hydrogen ([H]) in the main fermentation products consistently decreases with methanogenesis inhibition, evidencing the existence of unaccounted [H] sinks. We hypothesized that inhibiting methanogenesis in rumen batch cultures would redirect [H] towards microbial amino acids (AA) biosynthesis as an alternative [H] sink to methane (CH4). The objective of this experiment was to evaluate the effects of eight inhibitors of methanogenesis on digestion, fermentation and the production of microbial biomass and AA in rumen batch cultures growing on cellulose. Changes in the microbial community composition were also studied using denaturing gradient gel electrophoresis (DGGE). Inhibiting methanogenesis did not cause consistent changes in fermentation or the profile of AA, although the effects caused by the different inhibitors generally associated with the changes in the microbial community that they induced. Under the conditions of this experiment, inhibiting methanogenesis did not increase the importance of microbial AA synthesis as a [H] sink.

RESUMO

[This corrects the article on p. 37 in vol. 6, PMID: 25699029.].

RESUMO

Objective. Evaluate the acid-base balance (ABB) in bovines with diarrheic backgrounds in four areas of Montería, Colombia. Materials and methods. From a total of 300 pregnant cows, 60 were selected with their newborns. A direct inspection was performed of vital signs on the calves and the ABB indicators were determined using a gasometric method. Data were processed by means of descriptive statistics and the Duncan test was used to differentiate between the averages. The degree of association was established between the ABB indicators in cows and calves by using the Pearson correlation and a comparison of proportions was performed on the indexes of the newborns. Results. Regarding the cows, the ABB indicators were found within the reference values; however, in the calves the pH, pCO2, HCO3-, the anion gap (AG) and the bases excess (BE) varied. A correlation was found between AG, BE and metabolic hydrogen ions (M*H). The AG in cows and calves showed notable differences (p<0.05) among the farms in the study. According to the numeric classification system, the suction reflect indicated a greater percentage of calves in group one. Conclusions. The ABB analyte measurement in cows was similar to the consulted reference; however, in calves some analytes did not coincide. This suggests metabolic acidosis in newborn calves due to the increase of AG and the decrease of BE. Additionally, its correlation with M*H opens the possibility of new proposals to determine ABB in bovines.

Objetivo. Evaluar el equilibrio ácido-básico (EAB) en bovinos con antecedentes diarreicos de cuatro zonas de Montería, Colombia. Materiales y métodos. De un total de 300 vacas preñadas se seleccionaron 60 vacas y sus recién nacidos. Se realizó una inspección directa de los signos vitales en terneros y los indicadores del EAB se determinaron mediante técnica gasométrica. Los datos se procesaron mediante estadística descriptiva y para la diferencia entre medias se empleó la prueba de Duncan. El grado de asociación se estableció entre los indicadores del EAB en vacas y terneros mediante la correlación de Pearson y una comparación de proporciones se realizó en los índices del recién nacido. Resultados. En las vacas, los indicadores del EAB se encontraron dentro de los valores de referencia; sin embargo, en los terneros varió el pH, pCO2, HCO3-, la brecha aniónica (AG) y el exceso de bases (EB). Se encontró correlación entre AG, EB e hidrogeniones metabólicos (H+M). El AG en vacas y terneros indicó diferencias notables (p<0.05) entre las fincas de estudio. De acuerdo con el sistema de calificación numérica, el signo reflejo de succión indicó el mayor porcentaje de terneros en el grupo uno. Conclusiones. La medición de los analitos del EAB en vacas fue similar a la referencia consultada; sin embargo, en terneros no coincidió con algunos analitos. Se sugiere acidosis metabólica en los terneros recién nacidos por el aumento del AG y descenso del EB, además, su correlación con los H+M abre la posibilidad de nuevas propuestas para la determinación del EAB en bovinos.

RESUMO

Maximizing the flow of metabolic hydrogen ([H]) in the rumen away from CH4 and toward volatile fatty acids (VFA) would increase the efficiency of ruminant production and decrease its environmental impact. The objectives of this meta-analysis were: (i) To quantify shifts in metabolic hydrogen sinks when inhibiting ruminal methanogenesis in vitro; and (ii) To understand the variation in shifts of metabolic hydrogen sinks among experiments and between batch and continuous cultures systems when methanogenesis is inhibited. Batch (28 experiments, N = 193) and continuous (16 experiments, N = 79) culture databases of experiments with at least 50% inhibition in CH4 production were compiled. Inhibiting methanogenesis generally resulted in less fermentation and digestion in most batch culture, but not in most continuous culture, experiments. Inhibiting CH4 production in batch cultures resulted in redirection of metabolic hydrogen toward propionate and H2 but not butyrate. In continuous cultures, there was no overall metabolic hydrogen redirection toward propionate or butyrate, and H2 as a proportion of metabolic hydrogen spared from CH4 production was numerically smaller compared to batch cultures. Dihydrogen accumulation was affected by type of substrate and methanogenesis inhibitor, with highly fermentable substrates resulting in greater redirection of metabolic hydrogen toward H2 when inhibiting methanogenesis, and some oils causing small or no H2 accumulation. In both batch and continuous culture, there was a decrease in metabolic hydrogen recovered as the sum of propionate, butyrate, CH4 and H2 when inhibiting methanogenesis, and it is speculated that as CH4 production decreases metabolic hydrogen could be increasingly incorporated into formate, microbial biomass, and perhaps, reductive acetogenesis in continuous cultures. Energetic benefits of inhibiting methanogenesis depended on the inhibitor and its concentration and on the in vitro system.