Avaliação in vitro de leguminosas taniníferas tropicais para mitigação de metano entérico / In vitro evaluation of the taninniferous tropical legumes in order to mitigate enteric methane

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Animals contribute to increasing the methane concentration in the atmosphere through the fermentation of livestock manure and the fermentation in the digestive tract, e.g, enteric fermentation. The enteric fermentation of ruminants, pseudoruminants (horses, donkeys, mules) and non-ruminants produce an average of 80 Tg/year of methane and comprise 28 % of global anthropogenic methane emission, from which 95% arise from ruminants. The aims of this study were (i) to scan new potential forage containing tannin, which may reduce enteric methane emission; (ii) to study the influence of those plants on methane production and fermentative parameters in vitro; (iii) to study the influence of those plants on the population of Fibrobacter succinogenes and the methanogen community in the fermentation fluid. The results are presented in the form of chapters, being the first objective studied described in the Chapter 3, in which refers to the characterization of the tannin-rich legumes Styzolobium aterrimum (STA), Styzolobium deeringianum (STD), Leucaena leucocephala(LEU), Mimosa caesalpiniaefolia Benth (MIC). They were appraised for the chemical composition, quantification of phenolic compounds and bioassay up to 96 h in vitro incubation using Cynondon x cynodon (CYN) as control, to evaluate the potential gas production, (A), lag phase (L), fractional rate of gas production (mü) and the gas increment due to PEG addition after 8, 24 and 48 h incubation of the five plants. Legumes showed better fermentative performance (except MIC) than the grass. However, each legumes fermentation was limited diferently by the presence of condensed tannin or the indigestible fiber or by the additive action of both. Among the plants, LEU showed good quality forage for protein supplementation in sheep diets as well as STA and STD as long there is an agriculture management to reduce indigestible fiber, specially ADF. MIC could be included in a sheep diet in low concentration, aiming not the protein supplementation, but exploiting it as an additive to methane mitigation. In Chapter 4 the second object is discussed describing an in vitro gas test to evaluate the four tannin-rich legumes (STA, STD, LEU and MIC), and CYN as control at two main time points: t1/2 (time of half maximal gas production) and 24 h, measuring total gas production , methane, ammonia, short chain fatty acids (SCFA), microbial mass growth (MM) and true substrate degradability (TSD). Methane production at t1/2 was reduced (P <0.05) with addition of legumes by 17 % but when related to TSD this reduction reached on average 50 % with LEU and STA and 37% with MIC and STD. LEU and STA caused a significant increase in MM followed by STD, MIC, and CYN. Additionally, high MM/SCFA ratios in t1/2 were found in LEU (14.7) and STA (14.1) and followed by STD (6.1), MIC (5.6) and CYN (4.6). The higher MM in LEU and STA suggested higher ATP production; however, the different proportion of the SCFA demonstrated different routes of ATP acquisition. Chapter 5 refers to the quantification of specific strains of rumen bacteria, which was performed using designed primers for detecting 16S rDNA gene sequences for methanogens and the cellulolytic bacteria Fibrobacter succinogenes by real-time polymerase chain reaction (qPCR). Also, the influence of those four legumes on the methanogenic community was investigated using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA gene. Methanogens at t1/2 were 2.0 fold and 0.9 fold lower with STA and LEU compared to the control, but they were 2.5 fold and 0.5 fold higher with MIC and STD. F. succinogenes population was 2.3 and 1.8 fold lower than the control when LEU and STA was applied. DGGE analysis of the methanogenic population resulted in different band patterns with treatments. CYN presented some strong bands, which became weaker with the legumes, except in STA. Some bands either disappeared, as in LEU, STA and MIC, or became weaker, especially in STA. MIC increased slightly the number of weak bands. It is confirmed that the studied taninniferous plants were able to reduce enteric methane with different fermentation products proportions, as well negatively affected F. succinogenes population and caused changes in the methanogenic community structure

ASSUNTO(S)

ovinos fenólicos methane ovine ruminante metanogênicas methanonogens produção de gás tanino metano phenolic microorganisms gas production tannin ruminant microrganismos

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