Definition, Consequences and Prediction of an Elevated Ketone Body Status in High Yielding Dairy Cows

An elevated ketone body status in dairy cows is associated with detrimental effects on milk production, reproduction and health. However, critical threshold values reported vary widely. Based on that we have determined threshold values for ketone bodies in Holstein cows [n = 90; mean yield 9'500 kg energy-corrected milk/305 d], held in a research farm. Furthermore, we have studied consequences on productivity traits and disease incidence. In addition, we have investigated whether cows at risk can be detected prior to become ketotic, by monitoring body condition scores (BCS) and different blood and milk traits. BCS and ultrasonic measurements of backfat thickness and fat depth in the pelvic area were evaluated before calving and in wk 1, 4, 8, 12, 16 and 20 postpartum (p.p.).

Blood samples for determination of glucose, non-esterified fatty acids (NEFA), leptin, insulin, insulin-like growth factor-1 (IGF-1) and β-hydroxybutyrate (BHBA) were taken 2 wk ante partum and in wk 1–16 and 20 p.p. between 0730 – 0900. Milk samples for the determination of acetone (AC), fat, protein and lactose were taken in wk 1 – 16 and 20 p.p. Vaginoscopic examination and rectal palpation was done weekly. Threshold values for definition of ketotic status were calculated as mean + 2SD of all values p.p. and as upper 25% and 10% limits of maximal p.p. values for each individual cow and resulted in 0.40, 0.40 and 0.87 mmol/L for AC and 1.96, 2.30 and 3.51 mmol/L for BHBA, respectively. Ketone body concentrations above these thresholds did not occur before wk 2 p.p. Exceeding of these thresholds apart from the upper 10% limit for BHBA resulted in a decrease in milk yield (- 417 kg to – 654 kg/305 d; P < 0.05). AC concentrations above 0.40 mmol/L were associated with a 3.24 times higher risk for endometritis (P < 0.06). BCS at calving ≥ 3.50 and BCS loss > 0.5 during the first 8 wk of lactation were better associated with elevated ketones than ultrasonic measurements. Low glucose and high BHBA and AC concentrations in wk 1 p.p. were significant risk factors for a subsequently elevated ketone body status. The other measured metabolic and endocrine traits in blood plasma and milk components were not suitable to predict the development of ketosis. In conclusion, a routine determination of milk AC in the first wk after calving may help to predict the development of ketosis and to prevent production losses and endometritis, because cows with milk AC concentrations above 0.075 mmol/L were 5.6 times more likely to exceed the critical threshold later in lactation (P < 0.01). Determination of milk AC concentration very early in lactation can therefore be a tool in the herd-health management of high yielding dairy cows.