Ketosis as an adaptive mechanism: A Croatian dairy farm experience

The effect of β-hydroxybutyrate (BHB) level on reproductive parameters and milk production in pluriparous dairy cows was examined. The study was conducted on 231 Holstein-Friesian cows from the second to eighth lactation. Serum BHB was measured at 7 days in milk (DIM) with a Precision Xceed® BHBA meter and divided into positive (BHB ≥1.2 nmol/L) and negative (BHB < 1.2 nmol/L) groups for BHB levels. No differences between groups were detected for median days open (138 days), days open to first service (65 vs. 64 d), or all service conception rate (37.5% vs 37.6%). However, there was a trend (P=0.09) toward a 13.2% difference in the first service conception rates between groups. The positive group had a significantly higher percentage of postpartum disease, while parity had an influence on prolongation of days open and days open to first service, and disease influenced days open, regardless of BHB. The study indicated that elevated BHB values had no effect on milk yield or pregnancy percentage, suggesting that parity and postpartum disease are the variables that most influence reproduction success. Accordingly, elevated BHB might be considered an adaptive mechanism in otherwise healthy cows.