Analysis of the Gut Microbial Diversity of Dairy Cows During Peak Lactation by PacBio Single-Molecule Real-Time (SMRT) Sequencing

Effects of dietary zinc on the gut microbiome and resistome of the gestating cow and neonatal calf

Zinc is an essential trace element required in the diet of all species. While the effects of zinc have been studied in growing calves, little is known about the effect of zinc on the microbiota of the gestating cow or her neonatal calf. Understanding factors that shape the gut health of neonatal animals and evaluating the effect of dietary supplements in adult gestating animals is important in promoting animal health and informing feeding practices. The aims of this study were to determine the effect of dietary zinc on the microbiota and resistome of the gestating cow and calf. Gestating cows received standard (40 ppm) or high (205 ppm) dietary zinc levels from dry off to calving. Fecal samples were collected from cows upon enrollment and at calving and from neonatal calves. Fecal samples underwent 16S rRNA sequencing and a subset also underwent shotgun metagenomic sequencing. The effect of zinc supplementation on the diversity and composition of the cow and calf microbiome and resistome was assessed. Alpha and beta diversity and composition of the microbiota were significantly altered over time but not by treatment in the cows, with alpha diversity decreasing and 14 genera found at significantly higher relative abundances at calving compared to enrollment. Levels of 27 antimicrobial resistance genes significantly increased over time. Only a small number of taxa were differentially expressed at calving in treatment and control groups, including Faecalibacterium, Bacteroides, Turicibacter, and Bifidobacterium pseudolongum. No effect of the dam's treatment group was observed on the diversity or composition of the neonatal calf microbiota. The calf resistome, which was relatively rich and diverse compared to the cow, was also unaffected by the dam's treatment group. The impact of high levels of dietary zinc thus appeared to be minimal, with no observed changes in alpha or beta diversity, and few changes in the relative abundance of a small number of taxa and antimicrobial resistance genes.

Investigation of the vaginal microbiota of dairy cows through genetic sequencing of short (Illumina) and long (PacBio) reads and associations with gestational status

The vaginal microbiota has been shown to be important in local immune regulation and may play a role in reproduction and fertility. Next-generation sequencing (NGS) technologies have been used to characterize the bovine vaginal microbiota, mainly using short-read sequencing (Illumina). However, the main limitation of this technique is its inability to classify bacteria at the species level. The objective of this study was to characterize the bovine vaginal microbiota at the species level using long-read sequencing (PacBio) and to compare it with the results of short-read sequencing. In addition, the vaginal microbiota of cows that became pregnant after artificial insemination (AI) was compared with that of infertile animals. Thirteen Holstein cows had vaginal swabs collected prior to AI. DNA was extracted and subjected to Illumina and PacBio sequencing to characterize the V4 region and the entire 16S rRNA gene, respectively. PacBio sequencing yielded 366,509 reads that were assigned to 476 species from 27 phyla. However, none of the most abundant reads (>1%) could be classified at the species level. Illumina sequencing yielded more reads and consequently was able to detect a more observed species, but PacBio sequencing was able to detect more unique and rare species. The composition of the vaginal microbiota varies according to the sequencing method used, which might complicate the interpretation of results obtained in the majority of the current studies. The present study expands on the current knowledge of bovine microbiota, highlighting the need for further efforts to improve the current databanks.

Microbial Community Variations and Bioconversion Improvements during Soybean-Based Fermentation by Kefir Grains

Soybeans possess unexpected flavors and are difficult to be absorbed by the gastrointestinal tract. Kefir grain fermentation provides diverse strains and bioactive compounds, which may enhance flavor and bioaccessibility. Third-generation sequencing was applied to analyze the microbial diversity in milk and soybean kefir grains in this study. In both types of kefir grains, the most common bacterial genus was Lactobacillus, and their fungal communities were dominated by Kazachstania. Lactobacillus kefiranofaciens was the most abundant species in kefir grains, while Lactobacillus kefiri showed a higher proportion in soybean kefir grains. In addition, the quantification of free amino acids and volatile flavor compounds in soybean solution and soybean kefir have shown the increased content of glutamic acid and a decreased amount of unpleasant beany flavor compounds, demonstrating that the nutritive value and sensory properties of soybean can be improved by kefir grain fermentation. Finally, the bioconversion of isoflavones during fermentation and in vitro digestion was evaluated, suggesting that fermentation is beneficial for aglycone formation and absorption. To conclude, kefir fermentation is proposed to change the microbial structure of kefir grains, promote the nutritional value of soybean-based fermented products, and provide possible solutions for the development of soybean products.

The Rumen Specific Bacteriome in Dry Dairy Cows and Its Possible Relationship with Phenotypes

Most microbiome studies of dairy cows have investigated the compositions and functions of rumen microbial communities in lactating dairy cows. The importance of the relationships among hosts, microbiota, diet composition, and milk production remains unknown in dry dairy cows. Thus, in the present study, the composition of the rumen microbiome in cows from three dairy farms was investigated to identify core bacteria contributing to various physiological roles during rumen fermentation in dry dairy cows. The results indicated that ruminal fluid in dry dairy cows from different regional farms had core rumen microbiota that could be clearly distinguished from that of cows of the other farms. Further identification of key microorganisms associated with each farm revealed that Prevotella, Methanobrevibacter, Pseudobutyrivibrio, Ruminococcus, Bacteroides, and Streptococcus were major contributors. Spearman's correlation indicated that the abundance of genera such as Prevotella and Ruminococcus in dry dairy cows could indicate milk yield in the previous lactating period. Functional pathway analysis of the rumen bacterial communities demonstrated that amino acid metabolism and carbohydrate metabolism were the major pathways. Our findings provide knowledge of the composition and predicted functions of rumen microbiota in dry dairy cows from regional farms, which underscore the importance of the relationships among hosts, microbiota, diet composition, and milk production.

The Response of Microbiota Community to Streptococcus agalactiae Infection in Zebrafish Intestine

Recently, Streptococcus agalactiae has become a major pathogen leading to Streptococcosis. To understand the physiological responses of zebrafish (Danio rerio) to S. agalactiae, the intestinal microbiota composition of the intestine (12 and 24 h post-infection, hpi, respectively) in zebrafish infected with S. agalactiae were investigated. The intestinal bacterial composition was analyzed using PacBio high-throughput full-length 16S rRNA gene sequencing. The most predominant bacteria in the zebrafish intestine were the Fusobacteria phylum and Sphingomonas genus. S. agalactiae infection affected the composition of partially intestinal microbiota. At the species level, the relative abundance of the pathogenic intestinal bacteria Aeromonas veronii, S. agalactiae, and Clostridium tarantellae significantly increased after S. agalactiae infection (p < 0.05), while that of the beneficial intestinal bacteria Bacillus licheniformis, Comamonas koreensis, and Romboutsia ilealis significantly decreased (p < 0.05), showing that S. agalactiae infection aggravates the zebrafish disease through promoting abundance of other intestinal pathogenic bacteria. This study is the first PacBio analyses of the zebrafish intestinal microbiota community under pathogenic infection. Results suggest that the S. agalactiae infection alters the intestinal flora structure in zebrafish.

Invited review: Advances and challenges in application of feedomics to improve dairy cow production and health

Dairy cattle science has evolved greatly over the past century, contributing significantly to the improvement in milk production achieved today. However, a new approach is needed to meet the increasing demand for milk production and address the increased concerns about animal health and welfare. It is now easy to collect and access large and complex data sets consisting of molecular, physiological, and metabolic data as well as animal-level data (such as behavior). This provides new opportunities to better understand the mechanisms regulating cow performance. The recently proposed concept of feedomics could help achieve this goal by increasing our understanding of interactions between the different components or levels and their impact on animal production. Feedomics is an emerging field that integrates a range of omics technologies (e.g., genomics, epigenomics, transcriptomics, proteomics, metabolomics, metagenomics, and metatranscriptomics) to provide these insights. In this way, we can identify the best strategies to improve overall animal productivity, product quality, welfare, and health. This approach can help research communities elucidate the complex interactions among nutrition, environment, management, animal genetics, metabolism, physiology, and the symbiotic microbiota. In this review, we summarize the outcomes of the most recent research on omics in dairy cows and highlight how an integrated feedomics approach could be applied in the future to improve dairy cow production and health. Specifically, we focus on 2 topics: (1) improving milk yield and milk quality, and (2) understanding metabolic physiology in transition dairy cows, which are 2 important challenges faced by the dairy industry worldwide.