Seaweeds cows digestion methane production

Seaweed silage has potential to be an alternative feed ingredient for dairy cows. This study aims to investigate the effects of seaweed substrate on the ruminal bacterial composition and its impact on nutrient digestibility and methane mitigation. The cultivated Saccharina latissima and Alaria esculenta were preserved by freezing at - 40 °C or ensiling (16 °C, 3 months) with 4 different treatments (no additives, 0.4 % formic acids, lactic acid bacteria inoculant, LAB inoculant in the prewilted biomass). The bacterial composition in ruminal fluid after 48 h in vitro anaerobic incubation with seaweeds and common feedstuffs was analyzed using 16S rRNA amplicon sequencing (V3-V4) and qPCR. The nutrient digestibility was estimated using standard feed evaluation procedures. The results suggest that S. latissima was more digestible than A. esculenta and that the preservation treatments had only small effect on the ruminal bacteria compositions and nutrient digestibility. Also, A. esculenta showed no rumen degradable CP beside the soluble fraction, making it unsuitable as nutrient ingredients for dairy cows. The ruminal bacterial composition changed according to the different feed substrate. The dominant bacterial taxa when incubated with S. latissima belonged to the genus Prevotella (79 – 93 %), known for its ability to degrade polysaccharides in various ecosystems. Moreover, the fibrolytic bacteria including Fibrobacter succinogenes and Ruminococcus flavefaciens are > 2.5 Log2FoldChange higher when incubating with S. latissima than with A. esculenta. These bacterial taxa may play an important role in the in vitro organic matter digestibility, noted as 2 times higher in S. latissima compared to A. esculenta. Potential methane mitigation was observed through the qPCR results, with a significantly lower gene copies of Archaea 16S rRNA and methyl coenzyme-M reductase subunit A genes when the ruminal fluid was incubated with seaweeds. Our study suggested that ensiled S. latissima biomass can be included into the ruminant diet as an alternative forage-like ingredient with the potential of methane mitigation.