Effects of rare earth element lanthanum on rumen methane and volatile fatty acid production and microbial flora in vitro

Summary The objectives of the trial were to study the effects of rare earth element (REE) lanthanum (La) on the in vitro rumen methane (CH4) and volatile fatty acid (VFA) production and the microbial flora of feeds. Four feed mixtures with different levels of neutral detergent fibre (NDF), that is 20.0% (I), 31.0% (II), 41.9% (III) and 52.7% (IV), were formulated as substrates. Five levels of LaCl3, that is 0, 0.4, 0.6, 0.8 and 1.0 mmol/kg dry matter (DM), were added to the feed mixtures, respectively, as experimental treatments in a two-factor 5 × 4 randomized design. The in vitro incubation lasted for 24 h. The results showed that supplementing LaCl3 increased the total gas (p   0.05). It was concluded that LaCl3 decreased the CH4 production without negatively affecting feed digestion through manipulating rumen microbial flora when feed mixtures with different levels of NDF were used as substrates.