Metabolomic studies as a tool for determining the post-mortem interval (PMI) in stillborn calves.

BACKGROUND: Perinatal mortality may vary between herds, but the cost of deaths are always higher than value of the calf. When diagnosing the cause of a calf's death it is important to determine when it occurred, before or after calving. Metabolomics is widely used to identify many human diseases, but quite rarely applied in veterinary science. The aim of this study was to compare the metabolic profiles of calves with different times of death and those of calves born alive. Into the study, twenty one healthy controls (singleton, normal assisted calving, born alive) and 75 stillborn (SB) calves (with a gestation length of ≥260 days, SB, or dead within 6 h of birth) were enrolled. Plasma and urine from SB and control calves were investigated by proton nuclear magnetic resonance based metabolomic methods. SB calves were divided into four PMI groups. One PMI group included calves that died after calving and the other groups - three comprised in utero deaths, based on pathophysiological changes (lung inflation, autolysis in internal organs, hemoglobin imbibition in the pleura and aortic arch). Partial Least Squares - Discriminant Analysis models based on plasma metabolites were calculated, reflecting assumed data clustering. RESULTS: Twenty six metabolites in plasma and 29 in urine changed significantly with PMI according to one way analysis of variance. Half the metabolites in plasma and the majority in urine increased with PMI. Six metabolites increased simultaneously in plasma and urine: acetate, sn-glycero-3-phosphocholine (GPC), leucine, valine, creatine, and alanine. CONCLUSIONS: Post-mortem changes in calves were associated with molecular variations in blood plasma and urine, showing the greatest differences for the group in which the post-mortem pathological changes were the most advanced. The results of the study show that evaluation of calf plasma or urine may be used as a diagnostic method for the determination of the PMI. Moreover, the metabolites, which unambiguously increased or decreased, can be used as potential biomarkers of PMI.

Infection exposure, detection and causes of death in perinatal mortalities in Polish dairy herds.

The objective of this study was to determine the prevalence and types of infections in perinatal mortality (PM) cases from Polish dairy farms and the relevance of the presence of infection to the cause of death. This prospective longitudinal study was carried out on 121 PM and 21 control calves with a gestation of ≥260 days. Six control calves were euthanized and examined using the same protocol as for PM calves. Material was collected over a 20-month period between November 2013 and June 2015. The PM and control calves were collected from 29 to 5 herds, respectively. Blood samples from calves were tested for antibodies to Neospora caninum, glycoprotein B of BoHV-1, BVDV and SBV using ELISAs and Leptospira hardjo and Leptospira pomona with the microscopic agglutination test. Brain and kidney samples from all PM and six euthanized control calves were tested using real time PCR to detect Neospora caninum, pathogenic Leptospira spp., BoHV-1 and SBV; brain was examined histopathologically for detection of N. caninum cysts. Samples from eight inner organs from all PM and six control calves were cultured aerobically, anaerobically and microaerobically. Ear samples from all PM and control calves were tested for BVDV using an antigen ELISA. In total, 21.5% of PM calves were infected (antigen and/or antibody-positive) in utero; none of the control calves were infected. Direct evidence of infection (culture, Ag-ELISA, PCR, histopathology) was detected in 9.1% of PM calves. Gestation length in infected singletons was shorter than in uninfected singletons (274 ± 8 vs. 279 ± 7 days; P < 0.01). The odds ratio for diagnosis of infection in single pregnancies ≤275 days was 3.75 (95% CI:1.2-12.1), (P < 0.05). Infection was the cause of death in 10% of calves. The most common infections detected in these Polish PM calves were parasitic (11.6% of PM cases), viral (7.4%) and bacterial (5%). This study demonstrated that indirect evidence of infection is detected more frequently than direct, coinfection is rare, infection is rarely accompanied by gross lesions and is rarely a cause of death in cases of PM.