Effects of energy supply and nicotinic acid supplementation on phagocytosis and ROS production of blood immune cells of periparturient primi- and pluriparous dairy cows.

Effects of energy supply and nicotinic acid (NA) supplementation on the phagocytic activity of polymorphonuclear leukocytes (PMN) and peripheral blood mononuclear cells (PBMC), and on ROS production in PMN of periparturient cows differing in parity were examined. 29 pluriparous and 18 primiparous cows were allocated to four different feeding groups from 42days prepartum until 100days postpartum. They were fed either a ration with a low concentrate proportion of 30% (LC) or a high concentrate proportion of 60% (HC). After parturition all animals received 30% concentrate which was increased to 50% either within 16 (LC) or within 24days (HC). The different concentrate feeding strategies aimed at triggering differences in postpartum lipolysis. Half of the animals per group were supplemented with 24g per day of NA from 42days prepartum until 24days postpartum. All investigated parameters varied significantly over time compared to parturition (p<0.05). Numbers of phagocytosing PMN and PBMC increased in the course of the experiment, whereas the amount of engulfed bacteria per cell decreased between 42 and 11days prepartum. Percentage of basal ROS producing PMN decreased strongly before parturition and reached initial values only at 28days in milk again. Mean fluorescence intensity (MFI) in these ROS producing cells, however, increased before parturition. Oxidative burst stimulation in PMN was reduced around parturition but the amount of ROS produced in the stimulated cells was increased. Pluriparous cows exhibited higher numbers of basal ROS producing PMN and phagocytic PBMC. NA supplementation influenced phagocytosis in blood leukocytes.