Research Article Received: 10 July 2014

Revised: 28 October 2014

Accepted article published: 22 November 2014

Published online in Wiley Online Library:

(wileyonlinelibrary.com) DOI 10.1002/jsfa.7016

Effects of condensed tannin fractions of different molecular weights from a Leucaena leucocephala hybrid on in vitro methane production and rumen fermentation Mookiah Saminathan,a Chin Chin Sieo,a,b Norhani Abdullah,b,c Clemente Michael Vui Ling Wongd and Yin Wan Hoa* Abstract BACKGROUND: Molecular weights (MWs) and their chemical structures are the primary factors determining the influence of condensed tannins (CTs) on animal nutrition and methane (CH4 ) production in ruminants. In this study the MWs of five CT fractions from Leucaena leucocephala hybrid-Rendang (LLR) were determined and the CT fractions were investigated for their effects on CH4 production and rumen fermentation. RESULTS: The number-average molecular weight (Mn ) of fraction F1 (1265.8 Da), which was eluted first, was the highest, followed by those of fractions F2 (1028.6 Da), F3 (652.2 Da), F4 (562.2 Da) and F5 (469.6 Da). The total gas (mL g−1 dry matter (DM)) and CH4 production decreased significantly (P < 0.05) with increasing MWs of the CT fractions, but there were no significant (P > 0.05) differences between the CT fractions and control on DM degradation. However, the in vitro N disappearance decreased significantly (P < 0.05) with the inclusion of CT fraction F1 (highest MW) compared with the control and other fractions (F2–F5). The inclusion of CT fraction F1 also significantly decreased (P < 0.05) total volatile fatty acid and acetic acid concentrations compared with the control. The acetic/propionic acid ratio was significantly decreased (P < 0.05) by fraction F1 but not by the control and other fractions (F2–F5). CONCLUSION: The CT fractions of different MWs from LLR could affect rumen fermentation and CH4 production, and the impact was more pronounced for the CT fraction with a higher MW. © 2014 Society of Chemical Industry Keywords: condensed tannin fractions; molecular weight; Leucaena leucocephala hybrid-Rendang; methane; volatile fatty acids

INTRODUCTION Methane (CH4 ) emissions are a primary environmental concern owing to their contribution to global warming and climate change. Methane is the second most important greenhouse gas and has a heat-trapping potential 34 times greater than that of carbon dioxide (CO2 ).1 Globally, ruminant livestock produce approximately 80 million metric tonnes of enteric CH4 annually, accounting for approximately 30% of the global anthropogenic CH4 production.2 Methane production during enteric fermentation in ruminants also contributes to a loss of energy of up to 12%.3 Thus the mitigation of CH4 production by ruminants not only reduces greenhouse gas emissions but also improves feed efficiency and reduces production cost. In recent years, there has been increasing interest in the exploration of plant extracts to reduce enteric ruminal CH4 emissions. Some studies have shown that forage legumes containing condensed tannins (CTs) suppress CH4 emissions in vitro4 – 6 and in vivo.7 – 10 Condensed tannin-rich forages have shown methanogenic toxicity, resulting in less CH4 formation in ruminants.4,11 Beauchemin et al.12 suggested that using an extract of CTs to reduce CH4 emissions may be a better alternative J Sci Food Agric (2014)

to feeding tannin-rich forages. Condensed tannins have both beneficial and adverse effects in CH4 mitigation and rumen fermentation depending on their concentration and composition in the diet.13 High concentrations of CTs (>50 g kg−1 dry matter (DM)) have long been recognized as ‘antinutritional’ factors owing to depression of feed intake and reduction in DM digestibility.14,15 In contrast, CTs at low ( 0.05) among the treatments. The acetate/propionate (A/P) ratio was only significantly reduced (P < 0.05) by the inclusion of F0 and fraction F1. Correlation between CT fractions and in vitro fermentation parameters The coefficients of correlation (r) between the CT fractions of different MWs and the in vitro fermentation parameters are presented in Table 5. The CT fractions of different MWs were strongly negatively correlated with total gas, total CH4 and total CO2 production. IVDMD and IVND were also negatively correlated with the CT fractions after 24 h of in vitro incubation. For the in vitro VFA concentrations, there was a negative correlation between the CT fractions and total VFAs, acetic acid, butyric acid and A/P ratio. In contrast, the CT fractions of different MWs were positively correlated with propionic acid, branched VFAs and other VFAs.

DISCUSSION The average MW and DP of CTs vary among plants.26 The MWs of CTs of birdsfoot trefoil range from 1800 to 2100 Da, while those from sainfoin are between 1800 and 3300 Da.38 In this study the MWs of the CT fractions ranged from 1265.8 Da in fraction F1 to 469.60 Da in fraction F5. The effects of CT fractions varying in MWs on ruminal CH4 production can be effectively studied by using an appropriate CT concentration which could produce maximal reduction in enteric CH4 with minimal detrimental effect on rumen fermentation. Thus in the present study a concentration of 30 mg g−1 DM of the CT fractions (F1–F5) was used following the optimal concentration of unfractionated CTs from LLR, which showed a promising response on CH4 mitigation with no adverse effect on DM digestibility, as reported by Tan et al.29 Huang et al.39 also showed that 30 mg g−1 DM of pure CTs from another L. leucocephala hybrid could decrease CH4 with minimal detrimental effect on rumen fermentation. The effects of CTs on CH4 reduction have been reported in several studies.4,8,29,40 In the present study the inclusion of different-MW CT fractions from LLR decreased CH4 production, with fractions of higher MWs exhibiting a greater decrease. The CT fraction F1 was more effective than the unfractionated CTs F0

© 2014 Society of Chemical Industry

J Sci Food Agric (2014)

Condensed tannin fractions from Leucaena leucocephala hybrid

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Table 2. Effects of unfractionated CTs and CT fractions of different MWs from LLR on total gas, CH4 and CO2 production Unfractionated CTs and CT fractions (30 mg g−1 DM) Parameter

0 mg (control)

Total gas (mL g−1 DM)a Total CH4 (mL g−1 DM)a CH4 /total gas (mL mL−1 ) Total CO2 (mL g−1 DM)a c (h−1 )b

Unfractionated CTs (F0)

73.00a 13.15a 0.180a 19.96a 0.035a

64.67c 9.13d 0.141c 16.33 cd 0.020d

F1

F2

57.00e 8.07e 0.141c 14.97d 0.019d

F3

F4

61.67d 67.00bc 9.20d 9.35 cd 0.149bc 0.140c 16.09 cd 17.37bc 0.019d 0.023 cd

F5

67.33bc 10.27bc 0.152bc 18.55ab 0.028b

69.67b 11.06b 0.159b 19.03a 0.025bc

SEM

P value

1.129 0.361 0.003 0.444 0.002

Effects of condensed tannin fractions of different molecular weights from a Leucaena leucocephala hybrid on in vitro methane production and rumen fermentation.

Molecular weights (MWs) and their chemical structures are the primary factors determining the influence of condensed tannins (CTs) on animal nutrition...
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