Oxylipid profiles of dairy cattle vary throughout the transition into early mammary gland involution.

Successful lactation in multiparous dairy cattle relies on a well-managed dry period that allows the mammary gland to remodel and regenerate between lactations. Oxylipids are potent inflammatory mediators that are capable of regulating all aspects of inflammation. Although an oxylipid profile has been documented for periparturient and lactating cattle, little work has been done to define the profile of cows in the early dry period. Therefore, our group aimed to characterize the oxylipid profile in healthy cows during the transition into early mammary gland involution. Plasma samples were collected from 10 healthy Holstein dairy cows via coccygeal venipuncture 6 d before dry-off (d -6), at dry-off (d 0), and 1 (d +1), 2 (d +2), 6 (d +6), and 12 (d +12) d after the dry-off date. Liquid chromatography-mass spectrometry was used to quantify select monounsaturated fatty acids, polyunsaturated fatty acids, and saturated fatty acids, whereas oxylipids were quantified using liquid chromatography-tandem mass spectrometry. The results of this study revealed a unique profile of pro- and anti-inflammatory oxylipids throughout the transition from late lactation into the dry period. Many compounds reached the highest concentrations of the study at d +1, d +2, or d +12, whereas others reached the lowest concentrations at d +12. The characterization of this profile allows for further understanding of the physiology of early mammary involution. Future studies should investigate how the oxylipid profile of early mammary involution may affect the health and productivity of dairy cows.