Effects of Graded Levels of Mimosa (Acacia mearnsii) Tannin Purified with Organic Solvents on Gas, Methane, and In Vitro Organic Matter Digestibility of Eragrostis curvula Hay

The higher contribution of methane (CH4) to global anthropogenic potential is a cause of concern to livestock producers. Mimosa tannin gained recent acceptance as an additive for enteric CH4 mitigation. However, rumen fermentation and digestibility are compromised when large quantities of tannins are supplemented due to the presence of hydrolysable tannin and other non-tannin molecules in mimosa extract, which are toxic to animals. Purification could eliminate the toxins, and thus, reduce the CH4 yield without negative effects on rumen microbial activities and organic matter degradation. The Soxhlet extraction method was used to purify the tannin using organic solvents (ethyl acetate and pentanol). The unpurified, ethyl acetate purified, and pentanol purified tannins at the dosages of 10, 20, 30, and 40 g/kg DM of substrate (Eragrostis curvula hay) were evaluated for gas, CH4, and in vitro organic matter digestibility (IVOMD) in comparison with substrate alone. Gas kinetics were tested using a simple exponential model with lag. The results showed that compared with control, gas, CH4, IVOMD, CH4/gas, CH4/IVOMD, gas/IVOMD, asymptotic gas volume (v), and rate of gas production (k) decreased (p < 0.01) linearly with the increase in the inclusion levels of all tannin extracts. Also, ethyl acetate purified and pentanol purified tannin extracts reduced gas and CH4 at lower dosage (30 g/kg DM) compared to unpurified tannin extract at a higher level (40 g/kg). Pentanol purified tannin was more effective at lower dosage (20 g/kg DM) in terms of CH4/gas and CH4/IVOMD. It was concluded that the purification of mimosa tannin with ethyl acetate and pentanol reduced potential gas production and CH4 without much reduction in substrate digestibility when up to 30 g/kg DM of feed was used. Lower inclusion levels of ethyl acetate and pentanol purified extracts could give a similar result with a higher dosage of unpurified tannin.

Characterization, Density and In Vitro Controlled Release Properties of Mimosa (Acacia mearnsii) Tannin Encapsulated in Palm and Sunflower Oils

Simple Summary

The utilization of tannin in mitigating enteric methane suffers a setback in terms of dietary intake and digestibility because of the tannin’s astringency and instability in the gastrointestinal tract. Microencapsulation of tannin using lipids could mask its bitter taste and ensure its controlled release at the target site. This study aimed to encapsulate Acacia mearnsii tannin extract with palm and sunflower oils, and to evaluate the efficacy of the encapsulated tannins with regards to encapsulation efficiency, density, and release of tannin in media, simulating the rumen, abomasum and the small intestine. Mimosa tannin was encapsulated in palm oil or sunflower oil using a double emulsion method. The findings showed that encapsulated mimosa tannins in the palm oil and sunflower oil had high encapsulation efficiencies with smaller sizes and were lower in density compared to the unencapsulated mimosa tannin. The amount of tannins released by the unencapsulated tannin after 24 h in rumen (94%), abomasum (92%) and small intestine (96%) simulated buffers, were reduced to 24%, 21% and 19%, respectively, for the sunflower oil microparticle and 18%, 20% and 16%, respectively, for the palm oil microparticle in the same buffers and periods. Palm oil and sunflower oil successfully encapsulated the mimosa tannin and controlled its release in the gastrointestinal tract simulated media without compromising rumen fermentation.

Abstract

Tannin has gained wider acceptance as a dietary supplement in contemporary animal nutrition investigations because of its potential to reduce enteric methane emission. However, a major drawback to dietary tannin intake is the bitter taste and instability in the gastrointestinal tract (GIT). The utilization of fats as coating materials will ensure appropriate masking of the tannin’s aversive taste and its delivery to the target site. The aims of this study were to encapsulate mimosa tannin with palm oil or sunflower oil, and to assess the microcapsules in terms of encapsulation efficiency, morphology, density, and in vitro release of tannin in media simulating the rumen (pH 5.6), abomasum (pH 2.9) and small intestine (pH 7.4). The microencapsulation of mimosa tannin in palm or sunflower oils was accomplished using a double emulsion technique. The results revealed that encapsulated mimosa tannins in palm oil (EMT^P) and sunflower oil (EMT^S) had high yields (59% vs. 58%) and encapsulation efficiencies (70% vs. 68%), respectively. Compared to unencapsulated mimosa tannin (UMT), the morphology showed that the encapsulated tannins were smaller in size and spherical in shape. The UMT had (p < 0.01) higher particle density (1.44 g/cm³) compared to 1.22 g/cm³ and 1.21 g/cm³ for the EMT^S and EMT^P, respectively. The proportion of tannins released by the UMT after 24 h in the rumen (94%), abomasum (92%) and small intestine (96%) simulated buffers, reduced (p < 0.01) to 24%, 21% and 19% for the EMT^S and 18%, 20% and 16% for the EMT^P in similar media and timeframe. The release kinetics for the encapsulated tannins was slow and steady, thus, best fitted by the Higuchi model while the UMT dissolved quickly, hence, only fitted to a First order model. Sequential tannin release also indicated that the EMT^S and EMT^P were stable across the GIT. It was concluded that the microencapsulation of mimosa tannin in palm or sunflower oils stabilized tannins release in the GIT simulated buffers with the potential to modify rumen fermentation. Further studies should be conducted on the palm and sunflower oils microcapsules’ lipid stability, fatty acid transfer rate in the GIT and antioxidant properties of the encapsulated tannins.

Preparation and Characterization of Condensed Tannin Non-Isocyanate Polyurethane (NIPU) Rigid Foams by Ambient Temperature Blowing

Ambient temperature self-blowing mimosa tannin-based non-isocyanate polyurethane (NIPU) rigid foam was produced, based on a formulation of tannin-based non-isocyanate polyurethane (NIPU) resin. A citric acid and glutaraldehyde mixture served as a blowing agent used to provide foaming energy and cross-link the tannin-derived products to synthesize the NIPU foams. Series of tannin-based NIPU foams containing a different amount of citric acid and glutaraldehyde were prepared. The reaction mechanism of tannin-based NIPU foams were investigated by Fourier Trasform InfraRed (FT-IR), Matrix Assisted Laser Desorption Ionization (MALDI-TOF) mass spectrometry, and 13C Nuclear Magnetic Resonance (13C NMR). The results indicated that urethane linkages were formed. The Tannin-based NIPU foams morphology including physical and mechanical properties were characterized by mechanical compression, by scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). All the foams prepared showed a similar open-cell morphology. Nevertheless, the number of cell-wall pores decreased with increasing additions of glutaraldehyde, while bigger foam cells were obtained with increasing additions of citric acid. The compressive mechanical properties improved with the higher level of crosslinking at the higher amount of glutaraldehyde. Moreover, the TGA results showed that the tannin-based NIPU foams prepared had similar thermal stability, although one of them (T-Fs-7) presented the highest char production and residual matter, approaching 18.7% at 790 °C.