IL-1beta and IL-6 levels in dry period and acute phase response in early lactating dairy cows

During the peripartum, dairy cows often show an acute phase response (APR). APR severity and duration are related to health, liver metabolism, performance and body losses. Triggers of APR are pro-inflammatory cytokines (PIC), but scarce are the knowledge of their pattern of changes in transition period. To clarify this aspect, 10 multiparous cows were studied 4 wk before and after calving. Besides health status, feed intake, milk yield, rectal temperature, body weight and BCS, blood was frequently sampled to determine a large metabolic-inflammatory profile, in addition to IL-1 and IL-6. Cows were retrospectively classified into 3 groups according to IL-6 plasma levels in the last month of pregnancy: LO-IL (2 cows), IN-IL (4 cows) and UP-IL (4 cows). Data were processed by the MIXED repeated procedure of SAS. According to the ranking of cows, the average levels of IL-6 during last month of pregnancy were 159, 264 and 802 pg/ml for LO-IL, IN-IL and UP-IL groups respectively (P<0.05). IL-1 was well related to IL-6 (r =0.40; P<0.001) and showed a similar pattern of changes. In late pregnancy, levels of both PIC showed some fluctuations without any association to clinical diseases. In all groups, both PIC displayed a small and short-lived raise at calving time, often related to diseases. Thereafter, PIC levels in IN-IL and UP-IL decreased and differences between groups disappeared. Cows with higher PIC levels before calving had worse health status after calving, ate less, had higher rectal temperature, lost more body reserves and produced less milk. Contemporaneously, UP-IL cows showed more severe APR, as suggested by the marked and prolonged increase of haptoglobin and ceruloplasmin; the pattern of changes of some APR related parameters - as bilirubin (increase), zinc (reduction) and albumin (reduction) - confirm this status. Thus, the average IL-6 level at the end of pregnancy seems related to the higher susceptibility to inflammation at calving time and to the worsening of the health status and performance. Nevertheless, before calving no clear APR was detected, plasma ceruloplasmin had an higher level in UP-IL and IN-IL vs LO-IL, while albumin showed a progressive decrease in UP-IL 2 weeks pre-calving. Therefore, further studies are needed to clarify reasons of so different levels of PIC before calving and the link between high PIC level and increased susceptibility to inflammation.