PHYSIOLOGY College of Veterinary Medicine, China Agricultural University, Beijing, China The Influence of Intramammary Lipopolysaccharide Infusion on Serum Ca, P, Vitamin D, Cytokines and Cortisol Concentrations in Lactating Sows J. F. Wang 1,4 , M. Wang 1 , J. L. Ma 1 , L. G. Jiao 1 , X. Y. Zhou 2 and J. E. Lindberg 3 Addresses of authors: 1 College of Veterinary Medicine, China Agricultural University, Beijing, China; 2 Laboratory of Endocrinology, Peking Union Medical College Hospital, Beijing, China; 3 Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden; 4 Corresponding author: Tel.: +86 10 6273 1094; fax: +86 10 6273 1274; E-mail: jiufeng_wang@hotmail.com With 6 figures Received for publication June 24, 2005 Summary Ten multiparous lactating sows were used to investigate whether intramammary infusion of lipopolysaccharides (LPS; Escherichia coli 0111:B4; 2.0 lg/kg of body weight) would affect the circulating concentrations of Ca, P, 25- hydroxyvitamin D (25-OHD), tumour necrosis factor-a (TNF-a), interleukin-6 (IL-6) and cortisol. The sows were randomly allotted to either control group (control) or LPS- treated group with five individuals per group and were infused with either physiological saline solution or LPS solution. The rectal temperature and udder quarter appear- ance were recorded at 0 (just before infusion), 1, 3, 7, 12 or 24 h after infusion. Blood samples were taken at 0, 1, 3, 7, 12 or 24 h after infusion. Before infusion, the rectal tem- peratures of all sows were below 39.2°C. At 3 and 7 h after infusion, the sows in the LPS group had a rectal tempera- ture over 39.4°C. At 24 h after infusion, the rectal temper- atures returned to pre-infusion levels. Serum Ca and P concentrations in the LPS group decreased (P < 0.05) after LPS infusion compared with the control group at 1 h after infusion. No significant differences (P > 0.05) in the con- centrations of 25-OHD were observed between groups con- trol and LPS at any sampling time. Increased (P < 0.01) concentrations of serum TNF-a, IL-6 and cortisol were observed in the LPS group compared with the control group at 3 and 7 h after infusion respectively. In conclusion, the elevation of serum concentrations of TNF-a, IL-6 and cortisol and the alterations of circulating concentrations of Ca and P following LPS infusion indicate that the immune system has been activated and immune activation may affect macromineral homeostatic regulation, which might have important implications for metabolic health of lactating sows. Lowered serum Ca and P following immune activation also shows a causative mechanism whereby immune activa- tion increases the risk of secondary disorders such as mastitis-metritis-agalactia syndrome. However, immune activation did not affect circulating concentrations of vita- min D metabolites. Introduction Mastitis is a common problem worldwide with most cases of mastitis in sows caused by Escherichia coli (Persson et al., 1996). The loss of functional udder parenchyma, reduced milk production and quality, and the real, but nebulous, cost of maintaining reservoirs of contagious udder pathogens are important when considering the adverse effects of mastitis (especially subclinical mastitis; Tyler et al., 1992). It is notable that piglets sucking glands of sows with mastitis may suffer from reduced growth due to starvation and insufficient colostrum intake (Bertschinger, 1999; Hulten et al., 2003). Mastitis-metritis-agalactia syndrome (MMA) in sows, also described as puerperal septicaemia and toxaemia or peripar- turient hypogalactia syndrome, continues to be of economic importance in the pig breeding industry. The complicated aetiology of this disease and the route of infection are still matters of discussion but it is generally accepted that Entero- bacteriaceae, particularly Escherichia coli, are the most important cause for MMA. Lipopolysaccharide (LPS) is a proinflammatory molecule that is shed from the Gram-negative bacterial surface and is released after bacteriolysis or during periods of rapid bacterial proliferation (Rietschel et al., 1994). LPS are considered to cause most pathophysiological reactions during bacterial infections and stimulate mammary monocytes and macroph- ages to produce pro-inflammatory cytokines (Van Miert, 1995). During E. coli mastitis, LPS is thought to be the initiating factor of acute phase reaction (Burvenich et al., 2003), which is the response of the host to any tissue injury caused by trauma or inflammation (Van Miert, 1995). The susceptibility of lactating sows to infectious disease might be associated with metabolic disease (Waldron et al., 2003). Cows with milk fever (Curtis et al., 1985) or retained placenta (Schukken et al., 1989) are more likely to contract mastitis. Sandstedt et al. (1984) and Waldron et al. (2003) reported that in dairy cows, the concentrations of serum Ca and P decreased following immune activation. Numerous studies have shown that the concentrations of cortisol (Magnusson et al., 1994; U.S. Copyright Clearance Center Code Statement: 0931–184X/2006/5303–0113 $15.00/0 www.blackwell-synergy.com J. Vet. Med. A 53, 113–118 (2006) Ó 2006 The Authors Journal compilation Ó 2006 Blackwell Verlag, Berlin ISSN 0931–184X