Abstract:
Tannin extracts have wide biological activity in ruminant nutrition. The possibility of masking
their bitter taste and enhancing sustained release in the rumen can be achieved through
encapsulation. The objectives of this study were to prepare an encapsulated Acacia tannin
extract (ATE) suitable for ruminants using the solid-in-oil-in-water (S/O/W) method, and to
evaluate the microparticles in terms of morphology, encapsulation efficiency and in vitro
release under varying pH. Subsequently, the effect of the microparticles on rumen in vitro
gas and methane production would be evaluated. Lipid microparticles were prepared using
the double emulsion process with palm oil and lard, dichloromethane, and Tween80/
Span80 emulsifiers. The microparticles produced by S/O/W emulsion tended to be smaller
(P = 0.06), and had greater encapsulation efficiency compared with those produced by the
melt dispersion method. Scanning electron micrographs showed microparticles had stable
cylindrical and spherical shapes, with mean size of 34± 10.2 μm. Maximum encapsulation
efficiencies of 78.6% and 80.1% were obtained with lard and palm oil as lipid wall materials,
respectively, even under high core material loading percentage of 80%. Wall material type
did not affect the characteristics of microparticles. In acetate buffer, only about 20% of tannin
was released from the lipid-encapsulated microparticles into buffer media after 24 hours.
In contrast, about 90% of the tannin had been released into solution before eight hours in
the crude extract. Lipid-encapsulated ATE reduced rumen gas and methane production
in vitro (P <0.05) in both Eragrostis and total mixed ration (TMR) diet substrates, but the
magnitude of reduction was lower than that obtained when unencapsulated ATE was the
additive (10% vs 20% for total gas and 17% vs 24% for methane). Crude ATE and palm oil
encapsulated ATE reduced the concentration of methane in sampled gas (P = 0.054) when
fermenting the TMR substrate, but this effect was not observed in the Eragrostis substrate.
Ammonia nitrogen concentration was greater in encapsulated ATE compared with the
crude ATE (P <0.001). These results show that the lipid-encapsulated ATE produced smallsized
and more uniform microparticles, with high encapsulation efficiency compared with microparticles prepared by melt dispersion. Encapsulation of ATE enhanced the sustained
release of tannin in the rumen, and with the potential to improve gas production and reduce
methane production.
