Selected Alternative Feed Additives Used to Manipulate the Rumen Microbiome

In recent years, a boost in the ruminant population has been observed, and consequently, an increase in the animals’ demand for nutrients and methane emissions. Methane emission is generated during the microbial fermentation of feed in the rumen, and a percentage even up to 12% of the energy obtained by this process can be wasted. In addition, the use of antibiotics in animal husbandry is being increasingly restricted. restricted. As a result, there is a continuous search for innovative feed additives that can serve as alternatives to antibiotics, and will also be safe for both people and the environment. In the present review article, additives were selected on basis that, according to studies conducted so far, may positively affect the microbiome of the digestive system by improving indicators and/or reducing methane production. Among them, probiotics, prebiotics or their combination—synbiotics are at the forefront of research. However, additives in the form of algae or plant origin are also gaining ground in popularity, such as essential oils, fermented wheat straw or Gelidium amansii, due to their general recognition as safe (GRAS) for both humans and environment.

Algibacillus agarilyticus gen. nov., sp. nov., isolated from the surface of the red algae Gelidium amansii

A novel Gram-stain-negative, strictly aerobic, coccoid and agar-hydrolysing bacterium, designated RQJ05T, was isolated from the marine red algae Gelidium amansii collected from the coastal area of Rizhao, PR China. Cells of strain RQJ05T were approximately 0.8–1.0×1.3–3.0 µm in size and motile by means of a polar flagellum. Growth occurred at 4–33 °C (optimum, 25–30 °C), pH 7.0–8.5 (optimum, pH 7.5–8.0) and in the presence of 1.0–7.0 % (w/v) NaCl (optimum, 2.0–3.0 %). Strain RQJ05T showed oxidase-positive and catalase-negative activities. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain RQJ05T formed a phylogenetic lineage with members of the family Alteromonadaceae and exhibited 16S rRNA gene sequence similarities of 92.6, 91.3, 90.2 and 90.1 % to Catenovulum maritimum Q1T, Catenovulum agarivorans YM01T, Paraphotobacterium marinum NSCS20N07DT and Algicola sagamiensis B-10-31T, respectively. The major cellular fatty acids of strain RQJ05T were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0 and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The major polar lipids of strain RQJ05T were phosphatidylethanolamine, phosphatidylglycerol and two aminophospholipids. Strain RQJ05T contained Q-8 as the major respiratory quinone. The genomic DNA G+C content was 39.0 mol%. On the basis of genotypic, phenotypic and phylogenetic evidence, strain RQJ05T is presented as a representative of a novel species in a new genus, for which the name Algibacillus agarilyticus gen. nov., sp. nov. is proposed. The type strain is RQJ05T (=KCTC 62846T=MCCC 1H00352T).