Changes in interleukin-6 concentration in peripheral blood of pre- and post-partum dairy cattle and its relationship to postpartum reproductive diseases

Reproductive diseases after parturition are a serious problem in dairy cattle. It is important to predict postpartum reproductive diseases early and to develop prophylaxis. The objectives of this study were to demonstrate changes in the peripheral blood concentration of interleukin-6 (IL-6) before parturition, which was mainly produced by T helper 2 type (Th2) cells, and to investigate a correlation between the IL-6 concentration and the occurrence of the postpartum retained placenta, endometritis and/or follicular cyst in dairy cattle. Twenty-seven Holstein-Friesian cows were used for this study. Thirteen had no clinical disease, 8 had retained placenta, 4 were diagnosed with endometritis by vaginal inspection, and 2 were diagnosed with follicular cyst by rectal palpation at I and 2 months after parturition. Blood samples were collected 60 days pre- and post-partum. They used for IL-6, progesterone (P-4) and estradiol-17beta (E-2) concentration determination. This study showed that the IL-6 concentration prepartum was higher than postpartum. Low levels of IL-6 and P-4 in peripheral blood prepartum tended to affect retained placenta and a high level of IL-6 prepartum tended to affect endometritis. These results indicate that measurement of change in the IL-6 concentration during pregnancy is one useful tool for predicting crisis in postpartum reproductive diseases in dairy cattle.