The effect of herd-level passive immunity in dairy farms on survival probability during the first year of life.

This study examined the impact of passive immunity at the herd level on survival probability during the first year of life for successful passive immunity (SPI) farms (n=19), <20% of the proportion of newborn calves with serum immunoglobulin (Ig) G concentrations of <10.0 g/L, and failure of passive immunity (FPI) farms (n=20) with ≥20%. The proportions of serum IgG concentrations on SPI farms were clearly shifted toward the high-concentration strata compared with FPI farms. SPI farms showed significantly (P<0.001) higher survival probability than FPI farms. These results suggest that having the proportion of higher serum IgG concentrations at the herd level may increase survival probability.