Food Animal Internal Medicine Resident Iowa State University Ames, Iowa, United States
Abstract: Hypothesis/
Objectives: Severe gram-negative mastitis in dairy cattle is associated with altered inflammatory markers. The primary objective was to evaluate the effect of genetics on cytochrome P450 (CYP450)–derived inflammatory lipid mediators during mastitis. A secondary objective was to assess associations between lipid mediators and inflammatory markers. We hypothesized that genetic background would differentially influence inflammatory responses during experimental mastitis.
Animals: Twelve multiparous lactating Holstein cows (n=6/genotype) were enrolled, including cows with genetics conserved from 1964 (UH) and cows with contemporary Holstein genetics (CH). All cows were clinically healthy and managed under standardized conditions.
Methods: A controlled experimental mastitis challenge was performed by intramammary infusion of 100 CFU/mL of Klebsiella pneumoniae (P24 strain) into one mammary quarter. Milk and blood were collected at 0, 12, 24, 48, and 72 h post-challenge for analyses of CYP450-derived lipid mediators, acute phase proteins, and cytokines. Data was analyzed using two-way repeated-measures ANOVA with genetic group and time as fixed effects, with Tukey adjustment (α = 0.05).
Results: Clinical mastitis was induced in all cows, with fever by 12h post-challenge. Mammary inflammation was subjectively similar between groups. Plasma haptoglobin concentrations were greater in UH cows at 48 and 72 h (P = 0.004). Plasma and milk amyloid A concentrations were numerically greater in UH cows but did not differ (P > 0.05). Lipid mediator and cytokine analyses are pending.
Conclusions and Clinical Importance: UH cows exhibited a more robust inflammatory response than CH cows. Definitive conclusions await completion of CYP450 lipid mediator and cytokine analyses.
