Critical thresholds of nonesterified fatty acids and β-hydroxybutyrate in transition dairy cows for prediction of first service conception rate [Geçiş dönemi sütçü ıneklerde ılk tohumlamada gebe kalma oranını tahmin etmede esterlenmemiş yağ asitleri ve β-hidroksibütirat kritik eşik değerleri]

The objective of this study was to establish cow level critical thresholds for β-hydroxybutyrate (bhba) and nonesterified fatty acids (nefa) to predict conception to first service. the data were generated from 97 holstein cows (2 to 5 parities) on a large commercial farm. serum concentrations of bhba and nefa were measured in all cows on day 10 prepartum and,weeks 1,2,4 and 6 postpartum. nefa and bhba analyzed with receiver operator characteristic (roc) analysis to determine critical thresholds for predicting pregnancy to first service. nefa in weeks 4 and 6 postpartum were the only significant predictors identified in the roc analysis. optimum critical thresholds for nefa in weeks 4 and 6 were 201.15 μmol/l and 203.4 μmol/l,respectively (p<0.05). the critical threshold for serum bhba in the prepartum cohort was 600 μmol/l (p=0.1),which predicted conception to first service. logistic regression analysis indicated that the risk of conceiving was 82.4% and 88.6% lower for cows with nefa ≥201.15 in week 4 (or=0.176; p=0.001) and nefa ≥203.4 μmol/l in week 6 (or=0.114; p=0),respectively. in conclusion,nefa concentrations within 4 and 6 weeks after calving were associated with lower probability of pregnancy at the first ai. © 2016,veteriner fakultesi dergisi. all rights reserved.