Body condition score (BCS) changes and non-esterified fatty acids (NEFA) are good indicators for measuring lipomobilization during the transition period. The aim of this study was to establish the possible correlation between cows with a higher BCS during this period and their reproductive performance postpartum. A total of 47 Holstein dairy cows were randomly allotted into two groups according to their prepartum BCS, including: G1 (BCS 3.5 to 3.75, n = 20) and G2 (BCS >3.75, n=27). Moreover, another two groups were established at 14^th day postpartum: G3, 37 cows lost more than 0.75 points of BCS and G4, 10 cows lost 0.75 points or less. Blood samples were obtained from 10 to 7 days before expected calving, and 14 days postpartum in all groups and serum concentrations of glucose, β-hydroxybutyrate, NEFA, urea, calcium and hepatic enzymes, and reproductive parameters were determined. NEFA values showed that cows of G2 and G4 had a higher lipomobilization than G1 and G3. Moreover, cows with a BCS of more than 3.75 and NEFA values of more than 495 µmol/L prepartum had a higher risk of non-pregnancy at first AI, and there was an increase in the number of open cows at 150 DIM, this being the reason why the elimination rate due to non-pregnancy increases (20%) and their reproductive lives shorten.

Key words: Body condition score, Dairy cows, Fertility, Lipomobilization, Transition period