The influence of a dietary enterococcus faecium strain-based additive on the taxonomic and functional characteristics of the rumen microbiota of lactating cows

Today rations for dairy cows are designed to provide the highest growth rate and productivity in a short period of time. However, such intensive livestock farming affects, first of all, the health of animals, since metabolic pathways inherent in ruminants are disrupted. The use of 16S metagenomics approaches makes it possible to assess the genetic and metabolic diversity of the bovine microbiome, which allows identifying factors that can contribute to an increase in productivity and an improvement in the health of the host. In the feeding trial, dairy cows were fed with dietary probiotic Cellobacterin+ based on the Enterococcus faecium 1-35 strain (the winter-spring period of 2018, JSC PZ Plamya, Gatchinsky District, Leningrad Province). Two groups of ten Holsteinized black-and-white dairy cows ( Bos taurus taurus ) of the 2nd and 3rd lactation with an average annual milk yield of 7000-7500 kg were used. The basal diet was 10 kg compound feed, 2 kg yellow corn, 0.5 kg sunflower cake, 0.5 kg rapeseed cake, 1 kg hay, 25 kg grass silage, 1 kg beet molasses, and 0.2 kg MINVIT®-3 (Russia). In the morning, the test cows were fed with dietary Cellobacterin+ (OOO BIOTROF, St. Petersburg) at 40 g per cow. Cicatricial contents (10-50 g) were collected from three cows of each group at the end of the experiment. Fasting blood was taken for biochemical analysis from the tail vein with vacutainers. The blood was analyzed for total protein, total bilirubin, glucose, calcium, phosphorus, urea, reserve alkalinity, ketone bodies. The mass fraction of fat in milk was analyzed according to GOST 5867-90, protein according to GOST 23327-98, and the number of somatic cells according to GOST R 54761-2011. Total DNA from the studied samples was extracted using the Genomic DNA Purification Kit (Fermentas, Inc., Lithuania) according to the attached instructions. Amplification for subsequent NGS sequencing was run (a Veriti Thermal Cycler, Life Technologies, Inc., USA) using the eubacterial primers (IDT) 343F (5´-CTCCTACGGRRSGCAGCAG-3´) and 806R (5´-GGACTANVGGGT-WTCTAAT-3´) flanking the V1V3 region of the 16S rRNA gene. Metagenomic sequencing (a MiSeq system, Illumina, Inc., USA) was performed with a MiSeq Reagent Kit v3 (Illumina, Inc., USA). Chimeric sequences were excluded from analysis using the USEARCH 7.0 program (http://drive5.com/usearch/). The processing of the obtained reads using the bioinformatics platform CLC Bio GW 7.0 (Qiagen, the Netherlands) included overlapping, quality filtering (QV > 15), and primer trimming. The taxonomic affiliation of microorganisms to genus was determined using the RDP Classifier program (http://rdp.cme.msu.edu/). Mathematical and statistical processing of the results was carried out using the software packages Microsoft Office Excel 2003, R-Studio (Version 1.1.453) (https://rstudio.com). The mean values ( M ) and standard errors of the means (±SEM) were calculated. The results were deemed significant at p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }