PREVACCINATION BOVINE VIRAL DIARRHEA VIRUS TITERS AND SUBSEQUENT REPRODUCTIVE-PERFORMANCE IN DAIRY HEIFERS

The study was conducted to determine if there was a relationship betwe en prevaccination bovine viral diarrhea virus (BVDV) titers in 14 mont h-old dairy heifers and time open during first lactation. length of th e conception interval, fetal survival during the second pregnancy, and age at culling. Possible associations were analyzed using nonparametr ic survival methods and survival distributions were described using th e product-limit (Kaplan Meier) methods. Regression analysis was used t o estimate the correlation between pre- and postvaccination BVDV titer s three years after vaccination. Evidence of exposure to BVDV prior to 14 months of age was demonstrated by serum-virus-neutralization titer s greater than 1:4 for 97% and greater than or equal to 1:128 for 67% of the 72 heifers followed. No correlation was found for 38 pairs of p revaccination and postvaccination titers (p = 0.76). The risk of being culled was high for heifers (n = 41) with very low 1:2-1:8) or very h igh (greater-than-or-equal-to 1:256) titers, but low for heifers (n = 31 with moderate (1:16-1:128) prevaccination titers (p = 0.098). Risk of subsequent fetal loss was high for heifers (n = 30) with very low ( 1:2-1:16) or very high (greater-than-or-equal-to 1:256) prevaccination titers, compared to heifers (n = 24) with moderate (1:32-1:128) titer s (p = 0.084). These findings suggest that prevaccination exposure to BVDV eliciting either a very weak or a very strong serological respons e may contribute to subsequent reproductive inefficiency and an increa sed risk of culling.