Changes in various metabolic parameters in blood and milk during experimental Escherichia coli mastitis for primiparous Holstein dairy cows during early lactation

The objective of this study was to characterize the changes in various metabolic parameters in blood and milk during IMI challenge with Escherichia coli (E. coli) for dairy cows during early lactation. Thirty, healthy primiparous Holstein cows were infused (h = 0) with ~20-40 cfu of live E. coli into one front mammary quarter at ~4-6 wk in lactation. Daily feed intake and milk yield were recorded. At –12, 0, 3, 6, 12, 18, 24, 36, 48, 60, 72, 96, 108, 120, 132, 144, 156, 168, 180 and 192 h relative to challenge rectal temperatures were recorded and quarter foremilk was collected for analysis of shedding of E. coli. Composite milk samples were collected at -180, -132, -84, -36, -12, 12, 24, 36, 48, 60, 72, 84, 96, 132 and 180 h relative to challenge (h = 0) and analyzed for lactate dehydrogenase (LDH), somatic cell count, fat, protein, lactose, citrate, beta-hydroxybutyrate (BHBA), free glucose (fglu), and glucose-6-phosphate (G6P). Blood was collected at -12, 0, 3, 6, 12, 18, 24, 36, 60, 72, 84, 132 and 180 h relative to challenge and analyzed for plasma non-esterified fatty acids (NEFA), BHBA and glucose concentration. A generalized linear mixed model was used to determine the effect of IMI challenge on metabolic responses of cows during early lactation. By 12 h, E. coli was recovered from challenged quarters and shedding continued through 72 h. Rectal temperature peaked by 12 h post-challenge and returned to pre-challenge values by 36 h post-IMI challenge. Daily feed intake and milk yield decreased (P <0.05) by 1 and 2 d, respectively, after mastitis challenge. Plasma BHBA decreased (12 h; P <0.05) from 0.96 ± 1.1 at 0 h to 0.57 ± 0.64 mmol/L by 18 h whereas concentration of plasma NEFA (18 h) and glucose (24 h) were significantly greater, 11 and 27%, respectively, after challenge. In milk, fglu, lactose, citrate, fat and protein yield were lower whereas yield of BHBA and G6P were higher after challenge when compared to pre-challenge values. Changes in metabolites in blood and milk were most likely associated with drops in feed intake and milk yield. However, the early rise in plasma NEFA may also signify enhanced adipose tissue lipolysis. Lower concentrations of plasma BHBA may be attributed to an increase transfer into milk after IMI. Decreases in both milk lactose yield and % after challenge may be partly attributed to reduced conversion of fglu to lactose. Rises in G6P yield and concentration in milk after challenge (24 h) may signify increased conversion of fglu to G6P. Results identify changes in various metabolic parameters in blood and milk after IMI challenge with E. coli in dairy cows that may partly explain the partitioning of nutrients and changes in milk components after IMI for cows during early lactation.https://doi.org/10.1186/2049-1891-5-4

Gene network and pathway analysis of bovine mammary tissue challenged with Streptococcus uberis reveals induction of cell proliferation and inhibition of PPARγ signaling as potential mechanism for the negative relationships between immune response and lipid metabolism

<p>Abstract</p> <p>Background</p> <p>Information generated via microarrays might uncover interactions between the mammary gland and <it>Streptococcus uberis </it>(<b><it>S. uberis</it></b>) that could help identify control measures for the prevention and spread of <it>S. uberis </it>mastitis, as well as improve overall animal health and welfare, and decrease economic losses to dairy farmers. The main objective of this study was to determine the most affected gene networks and pathways in mammary tissue in response to an intramammary infection (<b>IMI</b>) with <it>S. uberis </it>and relate these with other physiological measurements associated with immune and/or metabolic responses to mastitis challenge with <it>S. uberis </it>O140J.</p> <p>Results</p> <p><it>Streptococcus uberis </it>IMI resulted in 2,102 (1,939 annotated) differentially expressed genes (<b>DEG</b>). Within this set of DEG, we uncovered 20 significantly enriched canonical pathways (with 20 to 61 genes each), the majority of which were signaling pathways. Among the most inhibited were <it>LXR/RXR Signaling </it>and <it>PPARα/RXRα Signaling</it>. Pathways activated by IMI were <it>IL-10 Signaling </it>and <it>IL-6 Signaling </it>which likely reflected counter mechanisms of mammary tissue to respond to infection. Of the 2,102 DEG, 1,082 were up-regulated during IMI and were primarily involved with the immune response, e.g., <it>IL6</it>, <it>TNF</it>, <it>IL8, IL10, SELL, LYZ</it>, and <it>SAA3</it>. Genes down-regulated (1,020) included those associated with milk fat synthesis, e.g., <it>LPIN1, LPL, CD36</it>, and <it>BTN1A1</it>. Network analysis of DEG indicated that <it>TNF </it>had positive relationships with genes involved with immune system function (e.g., <it>CD14, IL8, IL1B</it>, and <it>TLR2</it>) and negative relationships with genes involved with lipid metabolism (e.g., <it>GPAM</it>, <it>SCD</it>, <it>FABP4</it>, <it>CD36</it>, and <it>LPL</it>) and antioxidant activity (<it>SOD1</it>).</p> <p>Conclusion</p> <p>Results provided novel information into the early signaling and metabolic pathways in mammary tissue that are associated with the innate immune response to <it>S. uberis </it>infection. Our study indicated that IMI challenge with <it>S. uberis </it>(strain O140J) elicited a strong transcriptomic response, leading to potent activation of pro-inflammatory pathways that were associated with a marked inhibition of lipid synthesis, stress-activated kinase signaling cascades, and PPAR signaling (most likely PPARγ). This latter effect may provide a mechanistic explanation for the inverse relationship between immune response and milk fat synthesis.</p

Factors contributing to immunosuppression in the dairy cow during the periparturient period

The transition from late gestation to early lactation results in dramatic physiological changes including metabolic changes and immunosuppression in the dairy cow. As a result, cows are at a high risk for disease during this time. Evidence supporting a link between metabolic status and naturally occurring immunosuppression is growing. This review focuses on the impacts of metabolic status, and the metabolites that characterize it, on the immune response of cows during the transition period. Glucose is the preferred fuel for immune cells and its low concentration during the transition period may partly explain the naturally occurring immunosuppression at this time. To our knowledge, ketones are not utilized by immune cells and primarily have been shown to inhibit the immune response when concentration is relatively high. The effect of fatty acids on the immune system response remains unclear. Evidence suggests that the type of fatty acid can either stimulate (i.e. saturated fatty acids) or inhibit (i.e. unsaturated fatty acids) the immune response. We have suggested that an index for physiological imbalance (PI), based on circulating metabolites that characterize metabolic status, directly relates to mechanisms associated with the development of disease and is superior to calculated energy balance and therefore is a better predictor of risk of disease. The usefulness of the PI index as a predictor of risk of disease and the mechanisms associated with the links between degree of PI and immunosuppression for dairy cows during the transition period warrants further investigation

Development of the PlyC endolysin as a bovine mastitis therapeutic for lactating dairy cows

Bovine mastitis, defined as an inflammation of the cow’s mammary gland, is the most common and economically significant disease affecting dairy cattle and the leading cause of antimicrobial use on dairy farms. Streptococcus uberis is currently the most prevalent Gram-positive pathogen causing this infection. Recent growing concerns among consumers regarding the potential for antimicrobial resistance have led to the examination of alternative strategies for controlling mastitis. The streptococcal C1 bacteriophage endolysin, PlyC, is a cell wall hydrolase that rapidly lyses S. uberis and other susceptible streptococci on contact, and as such, represents an alternative to this conventional antibiotic therapy. Therefore, the objective of this study investigates PlyC as a novel antimicrobial enzyme against S. uberis mastitis. The activity of PlyC was determined by dose response and standard microbiological assays. Binding of PlyC in raw milk was visualized by fluorescent microscopy. Toxicity was evaluated on mammalian cells and in various in vivo models. Our results show that PlyC possesses potent lytic activity against all S. uberis strains tested. Despite the ability of other endolysins that are known to lyse S. uberis, none have yet successfully functioned in raw cow’s milk, presumably due to inactivation by native proteins and lipids. In contrast to the latter, PlyC attained three logs of killing at a dose of only two times the minimal inhibitory concentration when administered to raw, mastitic milk derived from clinically affected cows. Due to the absence of neutralizing antibodies that specifically target PlyC, the potential of this enzyme as a novel antimicrobial treatment is further bolstered. PlyC was found to be non-toxic as observed on a bovine mammary cell line and non-irritating as observed on rabbit epidermis and mucous membrane models. Taken together these in vitro and in vivo findings, PlyC is now ready to advance to S. uberis-associated bovine mastitis clinical trials, which will commence Fall 2019