Interaction Between a Mammary Immune Response to Lipopolysaccharide and Luteal Function in Lactating Dairy Cows

Abstract Text: In a previous study we observed negative effects of an intravenous injection of Escherichia coli lipopolysaccharide (LPS) on luteal size and blood flow (LBF) as well as on plasma P4 concentrations. Because there are several reports about negative effects of mastitis on fertility of dairy cows, the objective of the present study was to investigate if LPS applied into the mammary gland could also suppress luteal function. Each of 8 lactating dairy cows received once 200µg LPS into one quarter of the mammary gland on Day 9 of the estrous cycle (Day 1 = ovulation). Plasma cortisol (stress hormone) and haptoglobin (acute phase protein), both indicating a systemic immune response, as well as P4 were determined immediately before (0h), hourly until 9h, and 12h and 24h after administration of LPS. Luteal size and LBF were measured 0, 3, 6, 9, 12, and 24h after LPS-injection. Cows showed local and systemic symptoms (swelling of the udder, pyrexia, increased cardiac and respiratory frequencies), increased (P≤0.02) cortisol concentrations between 2 and 8h, and a fivefold increase (P=0.02) of haptoglobin between 0 and 24h after treatment. Plasma P4 increased between Hours 2 and 4, and decreased between Hours 4 and 6 after LPS exposure. There was no effect (P>0.05) of treatment on luteal size, but LBF increased (P=0.05) during the first 3h after LPS-injection, remained constant (P>0.05) between Hours 3 and 6, and decreased (P<0.0001) between Hours 6 and 12. Results indicate that in contrast to an intravenous injection the application of LPS into the mammary gland does not show an obvious suppression of luteal function, although inducing systemic effects.

Keywords: mastitis, corpus luteum