Transcriptomic analysis of peripheral leukocytes in dairy cows with and without evidence of metritis and associated early postpartum disease

The aim of this study was to describe associations between peripheral leukocyte gene expression and early postpartum disease in dairy cows with clinical metritis. The study was conducted in a conventional dairy in Washington state. Diseased cows ≤14 DIM were enrolled (n = 11) based on evidence of clinical metritis with or without comorbidity or prior treatments. Healthy cows (n = 9) were selected based on comparative DIM and lactation numbers to diseased cows. Blood was collected for a complete blood count, serum biochemistry, leukocyte isolation, and RNA extraction at enrollment and twice more at 6- to 8-d intervals. A total of 34,625 genes were considered and 55 were associated with health status by the Boruta all-relevant feature machine learning selection algorithm. These were filtered to the 15 most representative genes within the diseased cohort as compared with the healthy cohort. The top ranked gene during every rank or error test was PGLYRP1. Its associated protein, peptidoglycan recognition protein 1, and other immunomodulatory molecules associated with this study selectively enhance or alter host innate immune defense mechanisms and modulate pathogen-induced inflammatory responses. Host-defense peptides such as those associated with this study provide insight into individual and population-level markers of disease resilience that may help improve therapeutics, guide genetic selection, and clarify the burden of disease on animal well-being. This is particularly relevant to the dairy cow transition period with its metabolic and physiologic changes and associated increase in disease susceptibility.