Effect of a Probiotic Strain Administration in Different Feeding Phases on Α- and Β-Diversity and Gene Expression of the Rumen Microbiome in Lactating Cows

In cows, there is a drastic metabolic stress caused by violations of the rumen microbiome composition during lactation. The aim of the present study was to investigate the α-and β-diversity of the rumen microbiome of lactating cows using next-generation sequencing (NGS) and gene expression assessed by qPCR, as well as evaluation of the corrective properties of a probiotic strain introduced into the rumen. The results showed that the addition of the probiotic to the diet contributed to an effective increase in the fat content of milk during the early lactation period (P ≤ 0.05). The NGS-based analysis of the rumen microbiome of the studied cows using the 16S rRNA gene sequences showed that the Shannon and Chao1 indices of α-diversity of prokaryotic communities remained unchanged during various feeding phases, as well as due to the probiotic effects. In the early lactation period and under the probiotic's impact, the number of representatives of the Clostridia_UCG-014 and Clostridiaceae families declined by 2.4 and 1.6 times, respectively (in Group 2 as compared to Group 1, P ≤ 0.05). Expression of the bacterial Ldh-L and ldhD genes was lower by 2.9 and 13.5 times, respectively (P ≤ 0.05), when adding the probiotic to the diet in the early lactation period.