This study investigated the effects of repeated oronasal treatment with
lipopolysaccharide (LPS) on the humoral immune responses in saliva, vaginal mucus, and the plasma markers of the
acute phase response in periparturient dairy cows. One hundred pregnant Holstein cows were administered either 3 increasing doses of LPS (n = 50) as follows: 1) 0.01 µg/kg
body weight (BW) on d -28, 2) 0.05 µg/kg BW on d -25, and -21, and 3) 0.1 µg/kg BW on d -18, and -14, or sterile
saline solution (controls; n = 50) oronasally for 3 consecutive wk starting at 28 d before parturition. Intensive sampling was conducted on thirty cows (n = 15/group). Multiple saliva, vaginal mucus and blood samples were collected around parturition and analyzed for total
immunoglobulin-(Ig)A, plasma
serum amyloid A (SAA),
lipopolysaccharide-binding protein (LBP), anti-LPS
IgA,
IgG,
IgM, tumour
necrosis factor(TNF)-α, and
interleukin(IL)-1. Results regarding total
secretory IgA (
sIgA)
antibodies showed greater concentrations in the saliva and an overall tendency for higher total
sIgA in the vaginal mucus of the LPS-treated cows. Treatment had no effect on plasma
sIgA,
IgG,
IgM anti-LPS
antibodies,
haptoglobin, SAA, LBP, TNF-α, and IL-1. Treatments by time interactions were observed for SAA and IL-1 with lowered concentrations of both variables in the plasma of LPS-treated cows after parturition. Overall, repeated oronasal LPS treatment clearly enhanced total
sIgA antibodies in the saliva, stimulated their production in vaginal mucus shortly before calving, and lowered plasma IL-1 around parturition, but showed limited effects on markers of the
acute phase response in the plasma in dairy cows around parturition.