Effect of somatic cell scores on functional longevity of dairy cattle assessed by survival analysis

The objective of this study was to analyze the effect of somatic cell scores on functional longevity (FL) assessed using survival analysis. Longevity was measured as days of productive life. FL was obtained by longevity global correcting for milk production. Data of production and somatic cell count (SCC) were used (n=20.359), with date of first calving between 1988 and 2000. The weibull model studied factors: herd-year-season of calving (HYS), age at first calving (AFC), lactation number-stage of lactation (NS), annual change in herd size (CHZ), milk (MY), fat (FY) and protein (PY) yield. All the effects were significant (P< 0.001) and contributed to explain the differences on the relative risk of culling (RR). An increase in the SCC levels caused a greater RR. An important effect of SCC and udder depth in FL was observed. Cows with greater SCC had almost 4.0 times more RR and it was more evident in very deep udders animals