Uterine involution disturbances with concurrent fertility problems because of subclinical endometritis are often a reason for therapeutic measures or, even worse, for culling . Therefore, there is an urgency to develop reliable and comfortable early diagnostic tools. Previous studies have reported lower concentrations of tumor necrosis factor (TNF)-α, IL–1β, IL–6, and IL–8 before calving in cows that developed retained fetal membranes after parturition . In contrast, elevated serum and tissue concentrations for pro-inflammatory cytokines, including TNF-α, IL–1β, and IL–6, were observed in cows with metritis, endometritis, or subclinical endometritis . In cystic ovarian disease, another reason for infertility, cytokine expression was observed to be altered within the follicular structures .
The present study aimed to clarify whether serum concentrations of IL–1β, SP, and VIP change over time after calving and if these concentrations are correlated to puerperal diseases.
With respect to the concentrations of pro-inflammatory cytokines, our results could not show statistically significant changes within the first 20 days of calving. In contrast to previous studies, no statistically significant differences were observed between healthy and diseased cows. Nevertheless, when interpreting the results of related to IL–1β, we must consider that the IL–1β concentration in a considerable number of cows was under the detection limit (6.4 pg/ml). To our knowledge, this finding has not been reported previously. Additionally, there might be breed differences concerning the serum concentrations of cytokines. The aforementioned study in cows that were at a risk of fetal membrane retention involved Zebu breeds and other Indian crossbreds, in which retention of the fetal membranes is reported to be more common than in other breeds, such as Holstein Friesians (HFs) . Nevertheless, the central role of inflammatory processes and placental maturing in the physiology of release of fetal membranes have also been shown for HFs [1,2].
However, according to our results, IL–1β is not suitable as a diagnostic marker for uterine diseases within the first 20 days of calving.
VIP also seems to be of no significance either for uterine involution or for uterine health. Our results revealed no significant differences, according to time after calving or healthy or diseased condition. A study on VIP within the reproductive tract only refers to tissue distribution, not serum concentrations .
In contrast, with respect to SP, statistical analyses revealed significant changes over time for the first three puerperal weeks. SP and VIP typically are present within the vaginal and uterine tissues of cows ; in particular, the role of SP is postulated in cervical softening and birth . To our knowledge, the present study is the first to describe a time-related change in SP serum concentrations after calving. Increasing concentrations of this neuropeptide might be associated with uterine involution. Although the group comparison between healthy and diseased animals showed a barely significant difference, the difference may be significant if the number of examined animals could be increased. Future studies should therefore concentrate on the establishment of normative values in relation to breed, age, lactation status, and pregnancy, because previously published literature only refers to SP concentrations in calves .