RESUMO
Increased disease rates are commonly reported among high-yielding dairy cows in the transition period, extending from 3 weeks before to 3 weeks after calving, and characterized by the occurrence of an inflammatory response in terms of both positive and negative acute phase proteins (APP+ and APP-). To determine the above inflammatory response, the authors had developed the Liver Functionality Index (LFI), which defines the above condition on the basis of some APP- responses (albumin, cholesterol sensu stricto+bilirubin) during the first month of lactation. In this respect, low LFI values are associated to a high inflammatory response and vice versa. The relationship between LFI and inflammatory cytokine response was investigated from day -28 to day +28 with respect to calving in 12 periparturient dairy cows showing the six highest and six lowest LFI values within a cohort of 54 high-yielding dairy cows. The hypothesis being tested was that LFI and APP- on the whole could be used as readout of successful vs. non-successful adaptation to the transition period, with a strong association to disease occurrence. In fact, low LFI cows experienced many more disease cases (13 vs. 3 in high LFI Group) and related drug treatments till day +28. Interleukin-6 (IL-6) serum concentrations were always higher in low LFI cows (P<0.05 on day +28). The greater IL-6 levels were correlated with higher ceruloplasmin (APP+) and lower lysozyme serum concentrations (P<0.05 and <0.1, respectively). This latter finding was correlated with a clear role in vitro of lysozyme in a dose-dependent modulation of the inflammatory response of swine intestinal epithelial cells and bovine peripheral blood mononuclear cells. Hematological examinations showed no significant differences between the two groups under study. On the whole, our results indicate that LFI and LFI-related parameters could be used to identify cows at risk in the transition period toward an improved farm management. Also, our study indicates that disease cases in periparturient, high-yielding dairy cows are correlated with signs of accentuated IL-6 response and other markers of inflammatory phenomena. These likely start in the late lactation period or around dry-off, as suggested by our prepartal data, and proceed at much greater levels after calving.
