Author: David Van

The objective of this work was to study nutritional strategies for decreasing methane production by ruminants fed tropical diets, combining in vitro and in vivo methods. The in vitro approach was used to evaluate the dose effect of condensed tannins (CT) contained in leaves of Gliricidia sepium, Leucaena leucocephala, and Manihot esculenta (39, 75, and 92 g CT/kg DM, respectively) on methane production and ruminal fermentation characteristics. Tannin-rich plants (TRP) were incubated for 24 h alone or mixed with a natural grassland hay based on Dichanthium spp. (control plant), so that proportions of TRP were 0, 0.25, 0.5, 0.75, and 1.0. Methane production, VFA concentration, and fermented OM decreased with increased proportions of TRP. Numerical differences on methane production and VFA concentration among TRP sources may be due to differences in their CT content, with greater effects for L. leucocephala and M. esculenta than for G. sepium. Independently of TRP, the response to increasing doses of CT was linear for methane production but quadratic for VFA concentration. As a result, at moderate tannin dose, methane decreased more than VFA. The in vivo trial was conducted to investigate the effect of TRP on different ruminal microbial populations. To this end, 8 rumen-cannulated sheep from 2 breeds (Texel and Blackbelly) were used in two 4 × 4 Latin square designs. Diets were fed ad libitum and were composed of the same feeds used for the in vitro trial: control plant alone or combined with pellets made from TRP leaves at 44% of the diet DM. Compared to TRP, concentration of Ruminococcus flavefaciens was greater for the control diet and concentration of Ruminococcus albus was least for the control diet. The methanogen population was greater for Texel than for Blackbelly. By contrast, TRP-containing diets did not affect protozoa or Fibrobacter succinogenes numbers. Hence, TRP showed potential for mitigating methane production by ruminants. These findings suggest that TRP fed as pellets could be used to decrease methane production.

Tannins (hydrolyzable and condensed) are water-soluble polyphenolic compounds that exert antinutritional effects on ruminants by forming complexes with dietary proteins. They limit nitrogen supply to animals, besides inhibiting the growth and activity of ruminal microflora. However, some gastrointestinal microbes are able to break tannin-protein complexes while preferentially degrading hydrolyzable tannins (HTs). Streptococcus gallolyticus, Lonepinella koalarum and Selenomonas ruminantium are the dominant bacterial species that have the ability to degrade HTs. These tanninolytic microorganisms possess tannin-degrading ability and have developed certain mechanisms to tolerate tannins in feeds. Hence, selection of efficient tanninolytic microbes and transinoculation among animals for long-term benefits become areas of intensive interest. Here, we review the effects of tannins on ruminants, the existence and significance of tannin-degrading microorganisms in diverse groups of animals and the mechanisms that tannin-degrading microorganisms have developed to counter the toxic effects of tannin.

This study was conducted to determine whether feeding cinnamaldehyde (main component of cinnamon bark essential oil; Cinnamon cassia), condensed tannins from quebracho trees (Schinopsis balansae), or saponins from Yucca schidigera altered the milk fatty acid profile of dairy cows. For this purpose, 4 lactating cows were used in 4 x 4 Latin square design (28-d period) and fed a total mixed ration containing no additive (control), or supplemented with cinnamaldehyde (1 g/d; CIN), quebracho condensed tannin extract (150 g/d; 70% of tannins; QCT), or Yucca schidigera saponin extract (60 g/d; 10% of saponins; YSE). Results revealed no effects of feeding CIN or QCT on milk fatty acid profile. Supplementation with YSE resulted in some modifications of milk fatty acid profile as suggested by the reduced proportions of C6:0 (2.71 vs. 2.95%), C8:0 (1.66 vs. 1.89%), and trans-11 C18:1 (0.92 vs. 1.01%). Results show low potential of cinnamaldehyde, condensed tannins, and saponins to alter ruminal biohydrogenation process and modify the fatty acid profile of milk fat at the feeding rates used in this study. Further investigations are needed to determine the factors that limit the effects of these secondary metabolites on ruminal microbial populations involved in the biohydrogenation processes of unsaturated fatty acids.

The study was carried out to assess the effect of condensed tannins (CT) supplementation through leaf meal mixture (LMM) on feed intake, humoral [Immunoglobulin G (IgG)], cell mediated immune response (CMI) and faecal egg counts in Haemonchus contortus infected sheep. Eighteen sheep were randomly divided into three groups (negative control-NC, infected control-C and Infected treatment-T) of six animals in each group in a completely randomized block design for a period of 90 days. Twelve H. contortus infected adult sheep were allocated into two equal groups C and T, supplemented with 0 and 1.5 % of CT, respectively. Six non-infected sheep of similar age and body weight of NC group were included in this study to compare their immune response with H. contortus C and CT supplemented T groups. Intake of dry matter and organic matter (g day(-1) and % live weight) was statistically similar (P < 0.05) among the three groups. The anti-Haemonchus IgG and CMI response was higher in T group as compared to C group. The mean faecal egg counts was significantly (P < 0.001) higher in C group as compared to T group. It may be concluded that dietary supplementation of CT (1.5 %) through LMM improved humoral and CMI immune response and decreased worm load in H. contortus infected sheep.

The objective was to evaluate the effect of fodder tree species (FTS) with condensed tannin contents: Cordia elaeagnoides, Platymiscium lasiocarpum, Vitex mollis, and Haematoxylon brasiletto, on in vitro methane (CH4) production at 24 h post incubation. The analysis was performed using the in vitro gas production technique, with three levels of inclusion/species: 600, 800, and 1,000 mg and with 4 replicates/species/level of inclusion. The substrate was incubated at 39°C, and the gas and CH4 production were recorded at 4, 8, 12, and 24 h post incubation. The data collected was analyzed through Pearson correlation, polinomial regression and fixed effects models. There were negative correlations between FTS-total gas volume (r = -0.40; p<0.001); FTS-volume of CH4 produced (r = -0.40; p<0.001) and between the inclusion level-volume of CH4 produced (r = -0.20; p<0.001). As well as a positive correlation between hours post incubation-total gas volume (r = 0.42; p<0.001) and between hours post incubation-volume of CH4 produced (r = 0.48; p<0.001). The FTS: C. elaeagnoides, V. mollis, and H. brasiletto have potential, in the three inclusion levels analyzed, to reduce CH4 emission on in vitro trials (>32.7%), taking into account the total CH4 production at 24 h of the forage used as reference (Avena sativa). It’s suggested that C. elaeagnoides-according to its crude protein, neutral detergent fiber, and condensed tannins content- is the best alternative within the FTS analyzed, for feeding ruminants and for the control of CH4 emissions during the dry season.

Lotus pedunculatus (cv. Grasslands Maku) grown on acid low-fertility soil and containing high concentrations of condensed tannin (76-90 g/kg dry matter (DM] was grazed by growing sheep for 31-42 d periods in three experiments. In Expt 2 an additional group of lambs grazed areas oversown with white clover (Trifolium repens) and red clover (Trifolium pratense). Lambs were transferred from grazing ryegrass (Lolium perenne)-white clover straight on to lotus in all experiments (unconditioned sheep). In Expt 3 a second group was included which had grazed high-tannin lotus for a pre-experimental period of 8 weeks (conditioned sheep). Effects of condensed tannin on body and wool growth were assessed by studying responses to daily oral administration of polyethylene glycol (PEG; molecular weight 3350, 75-100 g/d). PEG forms a complex with condensed tannin, which is assumed to be inert in its passage through the digestive system, and so effectively reduces the nutritional effects attributable to high condensed-tannin concentrations. Live-weight gain (LWG) in the absence of PEG was low (27-125 g/d) for sheep grazing high-tannin lotus, and PEG administration increased LWG by 41-61 g/d and increased wool growth. In Expt 3, responses to PEG supplementation tended to be less with conditioned than with unconditioned sheep, indicating that conditioned sheep had partially adapted to the high-tannin diet. PEG supplementation had no effect on either LWG or wool growth of sheep grazing areas oversown with mixed clovers, confirming its effects as specific to forages containing condensed tannins. These experiments therefore conclusively show that high concentrations of condensed tannin induced by growing Lotus pedunculatus under low soil fertility conditions prevent maximum expression of LWG and wool growth in grazing sheep. These results contrast with high LWG (153-315 g/d) observed in growing sheep grazing the same lotus cultivar grown in high fertility soil and containing 20 g condensed tannin/kg DM, a level considered to be nutritionally beneficial.

We applied a taxonomic approach to select the Eugenia dysenterica (Myrtaceae) leaf extract, known in Brazil as “cagaita,” and evaluated its gastroprotective effect. The ability of the extract or carbenoxolone to protect the gastric mucosa from ethanol/HCl-induced lesions was evaluated in mice. The contributions of nitric oxide (NO), endogenous sulfhydryl (SH) groups and alterations in HCl production to the extract’s gastroprotective effect were investigated. We also determined the antioxidant activity of the extract and the possible contribution of tannins to the cytoprotective effect. The extract and carbenoxolone protected the gastric mucosa from ethanol/HCl-induced ulcers, and the former also decreased HCl production. The blockage of SH groups but not the inhibition of NO synthesis abolished the gastroprotective action of the extract. Tannins are present in the extract, which was analyzed by matrix assisted laser desorption/ionization (MALDI); the tannins identified by fragmentation pattern (MS/MS) were condensed type-B, coupled up to eleven flavan-3-ol units and were predominantly procyanidin and prodelphinidin units. Partial removal of tannins from the extract abolished the cytoprotective actions of the extract. The extract exhibits free-radical-scavenging activity in vitro, and the extract/FeCl3 sequence stained gastric surface epithelial cells dark-gray. Therefore, E. dysenterica leaf extract has gastroprotective effects that appear to be linked to the inhibition of HCl production, the antioxidant activity and the endogenous SH-containing compounds. These pleiotropic actions appear to be dependent on the condensed tannins contained in the extract, which bind to mucins in the gastric mucosa forming a protective coating against damaging agents. Our study highlights the biopharmaceutical potential of E. dysenterica.