The effect of new bovine viral diarrhea virus introduction on somatic cell count, calving interval, culling, and calf mortality of dairy herds in the Dutch bovine viral diarrhea virus–free program

Bovine viral diarrhea virus (BVDV) infection has a major effect on the health of cows and consequently herd performance. Many countries have implemented control or eradication programs to mitigate BVDV its negative effects. These effects dairy herds are well documented, but there is much less information about new introduction already participating in program. The objective our study was investigate BVDV-free Dutch program Longitudinal herd-level surveillance data were combined with create 4 unique sets, including monthly test-day somatic cell count (SCC) set, annual calving interval (CIV) culling risk (CR) quarterly calf mortality rate (CMR) set. Each database contained 2 types herds: that remained free during whole period (defined as herds), lost their status breakdown herds). date losing defined date. To compare herds, random artificially generated for by simple sampling from distribution month herds. SCC CIV before after compared through linear mixed-effects models Gaussian distribution, CR CMR modeled using binomial generalized models. explanatory variables all included type, status, year, effect. Herd size an variable SCC, CIV, model. Season Results showed lower CR, CMR, shorter than Within affected CMR. In year introduction, higher factor 1.011 [2.5th 97.5th percentile (95% PCTL): 1.002, 1.020]. Compared breakdown, higher, factors 1.170 PCTL: 1.120; 1.218) 1.096 1.048; 1.153), respectively. This reveals had average relatively small performance