ABSTRACT. In this study, blood serum and leukocyte samples were collected from 400 Holstein heifers, all of which appeared to be healthy. Antibodies (Ab) against bovine viral diarrhea virus (BVDV) were detected in 57 serum samples, and BVDV antigen (Ag) was detected in 38 leukocyte samples. There were statistically important differences between the average first insemination ages (FIT) of the BVDV (Ag-/Ab+) heifers (p<0.0001) (pregnant p<0.05, nonpregnant p<0.0001) and BVDV (Ag-/Ab-) heifers. The average conception rates (CR) of BVDV (Ag-/Ab+) heifers and BVDV (Ag-/Ab-) heifers were not significant statistically. There were statistically important differences in average FIT between persistent infected (PI) BVDV (Ag+/Ab-) heifers (p<0.0001; PI pregnant p<0.05, PI nonpregnant p<0.0001) and BVDV (Ag-/Ab-) heifers. No significant differences in average CR between PI BVDV (Ag+/Ab-) heifers and BVDV (Ag-/Ab-) heifers were found. The differences in average FIT between BVDV (Ag+/Ab+; p<0.0001; nonpregnant p<0.0001) and BVDV (Ag-/Ab-) heifers were important statistically. Although there were no BVDV (Ag+/Ab+) pregnant heifers, the differences in average CR between BVDV (Ag+/Ab+) pregnant heifers and BVDV (Ag-/Ab-) heifers were found to be statistically important (p<0.0001). We conclude that fertility is affected in heifers with BVDV (Ag-/Ab+, Ag+/Ab-and Ag+/Ab+). Bovine viral diarrhea virus (BVDV) has a high affinity for replicating cells. The virus therefore attacks germ cells and fetuses, negatively affecting calf health and reproductive performance of the herd [28]. Infection with BVDV yields different outcomes depending on the stage of pregnancy [32]. Several reports have investigated the effect of BVDV infection on reproductive parameters such as conception rate (CR) [19,34], and it has been concluded that BVDV has a negative effect on the fertility of cows and heifers [11], with field studies reporting up to a 44% decline in CR [23,40]. However, some experimental and field studies have found that BVDV infection does not affect the CR of heifers [22,26].In this study, blood serum and leukocyte samples were collected from 400 heifers in tie-stall barns in the Burdur Province area of SW Turkey. All had been fertilized for the first time. Antibodies (Ab) in the blood serum samples were searched for with the BVDV-enzyme linked immunosorbent assay (ELISA) (Ab) test, while antigen (Ag) in the leukocyte samples was searched for with the BVDV-ELISA (Ag) test. The serological and virological test results were sorted into groups, and the relationships between the fertility parameters of each group were evaluated.
MATERIALS AND METHODSAnimals: For the present study, blood serum and leukocyte samples were collected from 400 heifers between 13 and 24 months of age at 155 dairy farms in 22 residential areas (city center and villages bound to the center) that were registered with the Holstein Breeding Association in Burdur Province. After 60 days, a second set of blood serum and leukocyte samples were taken from the same animals. ...