Nutritional vitamin E or plant extracts affect the immune response and mammary epithelium integrity during intramammary lipopolysaccharide challenge in early lactation

Background: Early lactation is a period at risk for mastitis. Our objective was to investigate the influence of nutritional vitamin E and plant extracts on redox and immune status at the systemic and local mammary levels during an inflammatory challenge in dairy cows. Thirty-six Holstein cows were placed in three groups: a 'control' group (n = 11) unsupplemented; a 'vitamin E' group (n = 13), supplemented with 3000 IU/d for 4 weeks before calving and 1000 IU/d for 4 weeks after calving; and a 'plant extracts' group (n = 14) supplemented with 10 g/d for 4 weeks before and after calving. Lipopolysaccharide (LPS) from Escherichia coli was infused into a one-udder quarter of the cows 5 weeks after calving. Blood and milk samples were collected before and 4, 7, 9, 28, and 76 h after the LPS infusion. Results: In the plant extract group, antioxidant gene (NQO1), superoxide dismutase activity 4 hours after the LPS challenge and total antioxidant capacity were increased compared to the control group. In the vitamin E group, expression of the antioxidant gene (SOD3) and glutathione peroxidase activity were more elevated than in the control group. Systemic immunity appeared to be reduced by antioxidant supplementations, with a higher migration of classical neutrophils in the plant extract group and less ROS production of neutrophils in the vitamin E group. However, immune capacities were increased at the local level in classical neutrophils (ROS production and phagocytosis) in both the plant extract and vitamin E groups. Following the LPS infusion, supplementation did not reveal any differences in terms of rectal temperature, milk yield or milk cell counts, but it did have a positive effect on mammary epithelium integrity (lower milk Na+:K+ ratio and higher OCLN gene expression). In addition, the plant extracts stimulated the synthesis of milk constituents, with higher milk protein gene expressions (LALBA, CSN3, CSN1S1) and a tendency towards a higher lactose content in milk. Conclusion: The LPS challenge showed that vitamin E or plant extracts enhanced the local inflammatory response while preserving systemic antioxidant capacities, integrity of the mammary gland and the composition of milk, and thus possibly contributing to preventing mammary infection in early lactating dairy cows.