Oral challenge with increasing doses of LPS modulated the patterns of plasma metabolites and minerals in periparturient dairy cows

We showed recently that repeated oral exposure to LPS stimulated humoral immune responses in periparturient dairy cows. Here, metabolic and mineral responses to repeated oral administration of LPS were investigated. Sixteen clinically healthy, pregnant Holstein cows were orally administered 3 ml of saline solution (control) or 3 ml of saline solution containing 3 increasing doses of LPS, at 07:00 h, as follows: (i) 0.01 µg/kg body mass (BM) on d −14 and −10, (ii) 0.05 µg/kg BM on d −7 and −3, and (iii) 0.1 µg/kg BM on d 3 and 7 relative to parturition. Blood samples were measured shortly before, and at 8 different time-points after (up to 6 h), the first challenge of each LPS dosage to evaluate the post-challenge plasma profile, as well as weekly up to 4 wk postpartum. Results showed that oral administration of LPS lowered concentrations of non-esterified fatty acids ( P < 0.01) and β-hydroxy-butyrate ( P < 0.01) in the plasma, particularly after the third LPS challenge. Also, after the third oral LPS challenge, treatment tended to increase plasma glucose. Plasma calcium did not change, but concentrations of insulin ( P < 0.01) and zinc ( P < 0.01) were greater, while that of copper was lower ( P < 0.01) in the plasma of treated cows. This is the first report to indicate a potential role for repeated oral administration of LPS around parturition to modulate the profile of plasma metabolites and minerals postpartum.