Increased incidence of several economically important diseases (i.e. mastitis, metritis, displaced abomasum and ketosis) causes significant animal welfare problems and production losses in transition dairy cattle and decreases the availability of safe and nutritious food for a growing global population. A major underlying factor responsible for the development of transition cow disorders is metabolic stress, which occurs when cows fail to adapt physiologically to an increase in nutrient requirements needed for parturition and the onset of copious milk synthesis and secretion. Metabolic stress can be characterised as resulting from the combined effects of altered nutrient metabolism, dysfunctional inflammatory responses, and oxidative stress. Together, these factors form destructive feedback loops that exacerbate metabolic stress and cause health disorders in transition cows. A better understanding of how nutrition and immunology interact to influence metabolic stress will facilitate the development of control programs to improve transition cow health. The ability to detect signs of metabolic stress early enough in the dry period to implement needed management adjustments before calving will be the key to successful monitoring and intervention programs.
Coliform mastitis is a severe and sometimes fatal disease characterized by an unregulated inflammatory response. The initiation, progression, and resolution of inflammatory responses are regulated, in part, by potent oxylipid metabolites derived from polyunsaturated fatty acids. The purpose of this study was to characterize the biosynthesis and diversity of oxylipid metabolites during acute bovine coliform mastitis. Eleven cows diagnosed with naturally occurring acute systemic coliform mastitis and 13 healthy control cows, matched for lactation number and days in milk, were selected for comparison of oxylipid and free fatty acid concentrations in both milk and plasma. Oxylipids and free fatty acids were quantified using liquid chromatography-tandem mass spectrometry. All polyunsaturated fatty acids quantified in milk were elevated during coliform mastitis with linoleic acid being the most abundant. Oxylipids synthesized through the lipoxygenase and cytochrome P450 pathways accounted for the majority of the oxylipid biosynthesis. This study demonstrated a complex and diverse oxylipid network, most pronounced at the level of the mammary gland. Substrate availability, biosynthetic pathways, and degree of metabolism influence the biosynthesis of oxylipids during bovine coliform mastitis. Further studies are required to identify targets for novel interventions that modulate oxylipid biosynthesis during coliform mastitis to optimize inflammation.
Dietary ammonium chloride supplementation at a dose of 450 mg/kg may be necessary to achieve a urine pH<6.5 in goats. Further studies of ammonium chloride supplementation and urolithiasis in goats fed low-calcium diets are indicated.
BackgroundSevere mammary tissue damage during acute coliform mastitis in cattle is partially caused by oxidative stress. Although considered a gold standard biomarker in some human conditions, the utility of 15‐F2t‐Isoprostanes (15‐F2t‐Isop) in detecting oxidative stress in dairy cattle has not been validated.HypothesisConcentrations of 15‐F2t‐Isop in plasma, urine, and milk correlate with changes in oxidant status during severe coliform mastitis in cattle.AnimalsEleven lactating Holstein‐Friesian dairy cows in their 3rd–6th lactation.MethodsA case–control study using cows with acute coliform mastitis and matched healthy controls were enrolled into this study. Measures of inflammation, oxidant status, and redox status in plasma and milk samples were quantified using commercial assays. Plasma, urine, and milk 15‐F2t‐Isop were quantified by liquid chromatography/tandem mass spectrometry (LC‐MS/MS) and ELISA assays. Data were analyzed by Wilcoxon rank sum tests (α = 0.05).ResultsPlasma 15‐F2t‐Isop quantified by LC‐MS/MS was positively correlated with systemic oxidant status (r = 0.83; P = .01). Urine 15‐F2t‐Isop quantified by LC‐MS/MS did not correlate with systemic oxidant status, but was negatively correlated with redox status variables (r = −0.83; P = .01). Milk 15‐F2t‐Isop quantified by LC‐MS/MS was negatively correlated (r = −0.86; P = .007) with local oxidant status. Total 15‐F2t‐Isop in milk quantified by a commercial ELISA (cbELISA) was positively correlated with oxidant status in milk (r = 0.98; P < .001).Conclusions and Clinical ImportanceFree plasma 15‐F2t‐Isop quantified by LC‐MS/MS and total milk 15‐F2t‐Isop quantified by cbELISA are accurate biomarkers of systemic and mammary gland oxidant status, respectively. Establishing reference intervals for free and total 15‐F2t‐Isops for evaluating oxidative stress in dairy cows should currently be based on the LC‐MS/MS method.
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