Recipient Organization
MICHIGAN STATE UNIV
(N/A)
EAST LANSING,MI 48824
Performing Department
Large Animal Clinical Sciences
Non Technical Summary
Bovine mastitis is the most important infectious disease affecting both the quality and quantity of milk produced in the United States.Mastitis can cause destruction of milk synthesizing tissues, resulting in decreased milk production and altered secretion composition.On average, losses associated with mastitis will cost American dairy producers about 2 billion dollars each yeareach year. In spite of the dire economic impact of this disease on the dairy industry, the most widely accepted method of mastitis therapy is intramammary antibiotic treatment.This method is not always cost effective due to discarded antibiotic-contaminated milk during and after treatment.Also, the efficacy of such treatments is low during the lactating period, especially against major mastitis-causing pathogens such asEscherichiacoli.New therapeutic approaches clearly are needed to control mastitis, improve dairy farm profitability, and reduce the dairy industries' dependence on chemotherapy.Both the incidence and severity of mastitis is greatest during the transition period when cows are metabolically stressed and there are dramatic changes in lipid metabolism.Intense release of fats from adipose tissues can affect disease susceptibility by disrupting normal inflammatory responses that contribute to tissue pathology.Dysfunctional inflammatory responses are characterized by an imbalance of the robust initial response needed for pathogen clearance and the prompt return to immune homeostasis. This project will explore how changes in lipid metabolism can directly impact the efficiency of dairy cattle inflammatory responses when confronted with mastitis-causing bacteria. We will specifically determine how certain classes of lipid mediators change around this time of calving when cows are especially susceptible to disease.The project will also explore how the severity of coliform mastitis can be mitigated by nutritional supplementation with essential fatty acids that are known to optimize dairy cattle immune responses.A better understanding of nutritional-based strategies that can enhance the cow's resistance to disease may reduce the need for antimicrobial therapies while also improving the production efficiency of the US dairy industry.?
Animal Health Component
30%
Research Effort Categories
Basic
70%
Applied
30%
Developmental
0%
Goals / Objectives
Bovine mastitis is the most important infectious disease affecting both the quality and quantity of milk produced in the United States.Mastitis can cause destruction of milk synthesizing tissues, resulting in decreased milk production and altered secretion composition.Dysfunctional inflammatory responses are a major cause of pathology and are characterized by an imbalance of the robust initial response needed for pathogen clearance and the prompt return to immune homeostasis.Acute and uncontrolledEscherichia colimastitis, for example, often results in severe tissue damage and significant milk production losses in early lactation cows. Macrophages determine the character of the inflammatory response and monocyte/macrophages obtained from early lactation cows have exacerbated pro-inflammatory reactions which can contribute to disease pathogenesis. Previous studies by our group showed that the pro-inflammatory phenotype of blood monocytes is correlated to dramatic changes in the relative amounts of plasma omega 6 (n6) and omega 3 (n3) polyunsaturated fatty acids during the physiological transition from late gestation and into the early lactation period.However, the underlying mechanisms of how polyunsaturated fatty acid metabolism can influence inflammatory-based diseases in early lactation dairy cattle has not been explored in depth. In order to fully harness the potential health benefits of n6:n3 polyunsaturated fatty acid supplementation,there is a critical needto identify the amounts and ratio of fatty acid intake required to alter macrophage-derived oxylipid profiles with the capacity to regulate macrophage-driven inflammatory responses in dairy cows. This new information will positively impact the dairy industry by providing for the first time, science-based recommendations for n6 and n3 PUFA ratios that will mitigate inflammatory-based diseases such as mastitis through nutritional interventions.Therefore, thecentral hypothesisis that enhancing the n3 PUFA content in bovine macrophages will increase pro-resolving oxylipid pools and thus reduce exacerbated inflammatory responses associated with disease pathogenesis in transition cows. The hypothesis will be tested with the following specific:Determine the impact of altered macrophage fatty acid content on oxylipid biosynthesis and inflammatory intracellular signaling pathways.Determine how dietaryfatty acid intake can alter coliform-induced macrophage inflammatory responses through altered oxylipid biosynthesis.The immediate goals of this project are to not only identify how oxylipids profiles shift during times of increased susceptibility to disease, but also determine the potential impact that specific oxylipids have on macrophage inflammatory functions. The long-term goal is to improve mastitis prevention strategies and optimize production efficiency in the dairy industry.
Project Methods
This project is innovative because it will investigate the interactions among nutrition, lipid metabolism, and inflammation in the context of dairy cattle disease susceptibility using two complementary approaches based on in vitro and in vivo methodology.First, we developed a unique bovine macrophage in vitro model that will be used to determine how altering the cellular fatty acid composition of these immune cells can influence the production of oxylipids that impact the efficiency of the inflammatory response.To this end, our group has developed a new targeted lipidome strategy that can monitor how shifts in the fatty acid content of macrophages can impact directly the profile of pro- and anti-inflammatory oxylipids that are known to be involved with the pathogenesis of bovine mastitis. Monocyte-derived macrophages will be generated using well-established procedures and then exposed to fatty acid mixtures that reflect both the composition and concentration of plasma lipid fractions during the transition period.The fatty acid mixtures will either mimic the relative proportions of polyunsaturated fatty acids observed during intense lipid mobilization (higher n6:n3) or a lower n6:n3 content that can feasibly be achieved through dietary intervention.Several concentrations of the fatty acid mixture will be evaluated including those that reflect values observed either in early lactation when lipid mobilization is greatest (0.75 mM), peak lactation (0.5 mM) or late lactation (<0.25 mM).Control cultures will consist of macrophages cultured in the absence of fatty acid supplementation, but instead will be cultured with only albumin used to prepare the lipid mixtures.A subpopulation of cultured macrophages will be collected at over time following initial exposure to the lipid mixtures to verify when the fatty acid content of treated cells sufficiently reflects the content of peripheral blood mononuclear cells during the transition period.Once the fatty acid content of macrophages changes as a consequence of the polyunsaturated fatty acid supplementation, they will be analyzed for temporal changes in pro-inflammatory markers and oxylipid biosynthesis following endotoxin stimulation.Additional studies using live and FITC-labeled coliform will be conducted to assess changes in macrophage phagocytic and bactericidal capacity.The second approach will build upon the in vitro experiments by defining the composition and concentration of dietary fatty acid supplementation needed to alter both the lipid substrate availability and the ultimate impact on oxylipid biosynthesis.Dietary strategies that yields the most effective change in macrophage oxylipid biosynthesis and bactericidal functions will be assessed further for the ability to mitigate the detrimental effects of bovine coliform mastitis.