Short communication: Relationship between metabolic status and the milk concentrations of haptoglobin and lactoferrin in dairy cows during early lactation.

To investigate the relationship between metabolic status and the acute phase proteins haptoglobin (Hp) and lactoferrin (Lf) in milk, the concentrations of beta-hydroxybutyrate (BHBA), nonesterified fatty acids (NEFA) and Hp were determined in blood samples collected weekly from 4 wk prepartum until 12 wk postpartum. Haptoglobin and Lf were determined in weekly milk samples. The cows (n = 49) were retrospectively classified according to NEFA and BHBA concentrations using different time intervals and threshold values for NEFA and BHBA, respectively. For BHBA, 4 threshold concentrations, (0.8, 1.0, 1.2, and 1.6 mM) were evaluated either at the first week before calving, at wk 1 or 2 postpartum, or when considering the means of wk 2 and 3 postpartum. For NEFA, the tested thresholds were 0.5 and 0.6 mM at wk 1 prepartum, wk 1 or 2 postpartum, or the means of wk 1 and 2 postpartum. All variables showed changes during the interval of observation. Comparing the time course of the acute phase proteins in the subgroups classified according to BHBA or NEFA, consistently greater concentrations of Hp in serum and milk and of Lf in milk were observed in those animals with BHBA concentrations above 1.6 mM during the last week before calving (n = 3/47) than in those with BHBA concentrations below this threshold. For NEFA, analogous differences for Hp in both serum and milk (0.52 +/- 0.07 and 18.1 +/- 4.6 for NEFA >0.6 mM vs. 0.36 +/- 0.04 mg/mL and 8.46 +/- 1.63 microg/mL for NEFA <0.6 mM, respectively) and for Lf in milk (130 +/- 8.5 vs. 89.2 +/- 7.1 microg/mL, respectively) were detected when a threshold of 0.6 mM at wk 2 postpartum was used. Our results indicated that cows having BHBA and NEFA serum concentrations above these thresholds at defined times could be identified.