Association between prepartum nonesterified fatty acid serum concentrations and postpartum diseases in dairy cows

The objective of the present study was to quantify the relationships between prepartum nonesterified fatty acid (NEFA) concentrations and the development of subsequent diseases or culling and to identify the op-timal thresholds allowing identification of animals at high risk of developing postpartum diseases or being culled. A total of 1,299 Holstein cows from 50 commer-cial herds located around Saint-Hyacinthe (QC, Can-ada) were enrolled in this observational study. Blood samples were collected from enrolled cows between 1 and 14 d before calving for serum NEFA quantifica-tion. Data concerning postpartum diseases and culling were collected from computerized record systems. The association between prepartum NEFA concentrations and postpartum diseases and culling was quantified using generalized linear mixed models, accounting for parity, season, week of sampling, and herd. Optimal NEFA thresholds were evaluated with receiver opera-tor characteristic curves analysis for all diseases and then confirmed with generalized linear mixed models, considering NEFA as a categorical variable (high or low). Prepartum serum NEFA concentrations were as-sociated with diseases diagnosed during the first 30 d in milk (DIM) and culling within the first 50 DIM. The optimal NEFA threshold associated with diseases was >= 290 mu mol/L for retained placenta, >= 300 mu mol/L for metritis and abomasal displacement, and >= 280 mu mol/L for clinical mastitis and hyperketonemia. The level as-sociated with the occurrence of at least one of these diseases in the first 30 DIM was >= 280 mu mol/L, but it was >= 260 mu mol/L for culling in the first 50 DIM. No re-lationship was found between NEFA concentrations and reproductive tract diseases (purulent vaginal discharge or cytological endometritis) or subclinical intramammary infection. Despite the strong relationship between prepartum NEFA concentrations and many diseases, the NEFA optimal threshold accuracy found in our study was low. In conclusion, our results demonstrate a relationship between NEFA concentrations in the 14-d period before calving and the subsequent development of diseases and culling. Prepartum NEFA concentra-tions thresholds between >= 260 and 300 mu mol/L appear to be a strategic choice. However, considering the low accuracy, their use at the cow level should be performed with caution.