Milk microbiome in the first month of lactation and at weaning from ewes supplemented with zinc pre- and postpartum.

Mastitis is an important disease with economic and welfare implications in both clinical and subclinical states. The aim of this research was to sequence the hypervariable V4 region of the 16S rRNA gene to describe the microbial diversity and taxonomy of milk from clinically healthy ewes (Rambouillet, WF = 9; Hampshire, BF = 5). Experimental ewes represented a subset of a larger study assessing the impacts of divergent dietary zinc (Zn) concentrations [1 × National Academics of Sciences, Engineering, and Medicine (NASEM) recommendations = CON or 3 × NASEM recommendations = ZnTRT] throughout late gestation and lactation. Milk was collected at four periods during early lactation (18 to 24 h, 7 d, 14 d, and 21 d postpartum) and at weaning (84 ±â€…14 d postpartum). Somatic cell counts (SCC) were quantified, averaged, and classed (low: < 500 × 103; medium: 500 × 103 - 100 × 104; high: > 100 × 104 cells/mL). Milk samples (n = 67) were sequenced to identify bacteria and archaea; the most abundant phyla were Actinobacteria, Bacteroidetes, Cyanobacteria, Euryarchaeota, Firmicutes, Fusobacteria, Lentisphaerae, Proteobacteria, Spirochaetes, Tenericutes, Saccharibacteria TM7, and Verrucomicrobia. Mastitis pathogens were among the most relatively abundant genera, including Staphylococcus, Mannheimia, Corynebacterium, and Pseudomonas. Effects of breed, dietary Zn concentration, SCC class, and their two-way interactions on milk microbiome diversity and taxonomy were assessed within early lactation (using a repeated measures model) and weaning samples. Alpha-diversity metrics included Pielou's evenness, Faith's phylogenetic diversity, and Shannon's entropy indices. The main and interactive effects between Zn treatment, breed, SCC class, and period were variable in early lactation and not evident in weaning samples. Milk from BF ewes had increased Faith's phylogenetic diversity and Shannon's entropy, and differed in unweighted UniFrac composition (P ≤ 0.10). Milk from CON ewes had a reduced rate of composition change through early lactation (P = 0.02) indicating greater microbiome stability than ZnTRT ewe milk. These results support that milk is not sterile, and breed, dietary Zn concentration, and SCC class variably affect the milk microbiome. Findings from the current study provide important foundational insights into the effects of increased dietary Zn supplementation on longitudinal changes in the milk microbiome and associations with mammary gland health and mastitis.

Mastitis is an important disease with economic and welfare implications in both clinical and subclinical states. This research described the microbial diversity and taxonomy of milk collected from clinically healthy Rambouillet (WF; n = 9) and Hampshire (BF; n = 5) primiparous ewes in a longitudinal study involving differing dietary zinc concentrations [1 × National Academics of Sciences, Engineering, and Medicine (NASEM) recommendations, CON; 3 × NASEM recommendations, ZnTRT]. Milk was collected weekly during the first 3 wk of lactation and at weaning, and somatic cell counts (SCC) were classed (low, medium, high). Mastitis pathogens were among the most relatively abundant via amplicon sequencing, including Staphylococcus, Mannheimia, Corynebacterium, and Pseudomonas. Breed, zinc treatment, and SCC class effects on milk microbiome α-diversity and ß-diversity changes and taxonomy were assessed. These effects and their two-way interactions were limited but variable in early lactation samples and not evident in weaning samples. Notably, BF ewe milk samples had increased Faith's phylogenetic diversity and increased Shannon's entropy during early lactation, and CON ewe milk samples had a reduced rate of compositional change than ZnTRT samples. These results support the existence of a milk microbiome that is variably affected by breed, increased dietary zinc concentrations, and SCC class.

Genes involved in the cholecystokinin receptor signaling map were differentially expressed in the jejunum of steers with variation in residual feed intake.

The jejunum is a critical site for nutrient digestion and absorption, and variation in its ability to take up nutrients within the jejunum is likely to affect feed efficiency. The purpose of this study was to determine differences in gene expression in the jejunum of beef steers divergent for residual feed intake (RFI) in one cohort of steers (Year 1), and to validate those genes in animals from a second study (Year 2). Steers from Year 1 (n = 16) were selected for high and low RFI. Jejunum mucosal tissue was obtained for RNA-seq. Thirty-two genes were differentially expressed (PFDR≤0.15), and five were over-represented in pathways including inflammatory mediator, cholecystokinin receptor (CCKR) signaling, and p38 MAPK pathways. Several differentially expressed genes (ALOX12, ALPI, FABP6, FABP7, FLT1, GSTA2, MEF2B, PDK4, SPP1, and TTF2) have been previously associated with RFI in other studies. Real-time qPCR was used to validate nine differentially expressed genes in the Year 1 steers used for RNA-seq, and in the Year 2 validation cohort. Six genes were validated as differentially expressed (P < 0.1) using RT-qPCR in the Year 1 population. In the Year 2 population, five genes displayed the same direction of expression as the Year 1 population and 3 were differentially expressed (P < 0.1). The CCKR pathway is involved in digestion, appetite control, and regulation of body weight making it a compelling candidate for feed efficiency in cattle, and the validation of these genes in a second population of cattle is suggestive of a role in feed efficiency.