Dataset_Late embryonic losses
The dataset contains information obtained in an observational study run in a commercial dairy herd from Argentina to test the hypothesis that infections with Bovine Viral Diarrhea Virus (BVDV), Infectious Bovine Rhinotracheitis virus (IBRV), and Neospora caninum (N. caninum) are associated with the risk for Late Embryonic Loss (LEL) in grazing dairy cows. The objectives were to evaluate the association of BVDV, IBRV, and N. caninum with the risk for LEL. Additional objectives were to evaluate blood progesterone concentration at the time of LEL occurrence and to detect BVDV, IBRV and N. caninum in aspirated conceptuses from LEL cows. A prospective cohort study involving 92 cows (46 with LEL and 46 non-LEL) was run. The LEL was defined as a cow having an embryo with no heartbeat or with detached membranes or floating structures, including embryo remnants detected by ultrasonography (US) at 28-42 days post-AI, whereas a non-LEL was defined as cows with embryo heartbeats detectable by US at 28-42 d post-IA. Two blood samples were obtained from every cow, the first one, on the day of LEL detection by US (in LEL cows and paired non-LEL cows), and the second one, 28 d later. Serological diagnosis to BVDV, IBRV, and N. caninum infection was performed on all samples, and progesterone concentration was measured on the first sampling. Presence of BVDV, IBRV and N. caninum in aspirated conceptuses from LEL cows was evaluated by PCR. The associations of risk factors (serological titers, seroconversion, and progesterone) with LEL odds were assessed with logistic regression models. The risk for LEL was associated with the seroprevalence to BVDV in the second sampling (P=0.03), but not with seroprevalence to BVDV, IBRV, N. caninum in the first sampling, either IBRV or N. caninum in the second sampling. Also, the risk for LEL tended to be associated with seroconversion to BVDV (P=0.09). Conversely, the risk for LEL was not associated with seroconversion to IBRV or N. caninum. Progesterone concentration in blood was not associated with the risk for LEL and was similar in LEL and non-LEL cows (P=0.54). Finally, BVDV was only detected in conceptuses from seropositive LEL cows that seroconverted to BVDV. In conclusion, BVDV infection is a risk factor for LEL in dairy cows. Conversely, IBRV, N. caninum, and luteolysis seem not to play any role in LEL development.
Steps to reproduce
The dairy herd was visited every 2 weeks for pregnancy diagnosis by transrectal ultrasonography (US) at 28-42 d post-AI with a 7.5-MHz linear transducer (Esaote Tringa Linear Vet, Pie Medical, Maastricht, Netherland). Cows with embryos showing no heartbeats, or detached membranes or floating structures including embryo remnants were considered as Late Embryonic Loss. For every detected LEL case a NLEL control was included with a temporal matching (± 3 d around the date of the AI of the fertilizing service, and parity). The day when the conceptus was detected by US in cows with LEL (28-42 d post-IA) was considered as day 0. The conceptus was sampled on d 0 with a plastic catheter attached to an insemination pipette protected by a plastic sleeve inserted through the cervix into the uterus by transrectal guidance. Then, the plastic sleeve was punctured to expose the tip of the plastic catheter. After that, the insemination pipette was disassembled from the plastic catheter and removed from the uterus. Then a 60-ml plastic syringe was attached to the plastic catheter and used to aspirate the conceptus. Finally, the syringe attached to the plastic catheter was removed from the uterus, and the sampled conceptus was stored in a 1.5 ml plastic tube at 4°C. Cows (LEL and NLEL) were bled on day 0 and 28 days later for serological studies. Serological detection of BVDV and IBRV were performed by virus neutralization according to the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (OIE, 2018). The reciprocal of the highest serum dilution capable of neutralizing viral replication was considered as the neutralizing titer. Dilution of samples was performed in base 2, starting with a neutralizing titer of 1:2 up to a final neutralizing titer of 1:2048 for BVDV and from 1:2 to 1:512 for IRBV. Seroconversion was considered when a difference of three neutralizing titers between first and second sampling (28 d apart) was observed . Serological detection of N. caninum was performed by Indirect Fluorescent Antibody Test using a cut-off titer of 1:200 and processed to final titer . Seroconversion was considered when a difference in ≥ 2 titers was detected within 28 d . The presence of BVDV, IBRV and N. caninum in conceptuses was evaluated by PCR. Plasma progesterone concentration was measured by chemiluminescence (Immunoanalyzer Elecsys and Cobas E, Roche®, Mannheim, Germany). Logistic regression models were used to assess the associations of serological titers to BVDV, IBRV, and N. caninum at d0 and d28 (as continuous predictors) with the odds for LEL (model 1); to evaluate the associations of seroconversion (yes vs. no) to BVDV, IBRV and N. caninum (yes vs. no) with the odds for LEL (model 2), and to test the association between blood progesterone concentration (as continuous predictor) at d0 with the odds for LEL (model 3).