AbstractThe transition period, 3 weeks before and 3 weeks after calving, is inevitably
accompanied by a negative energy balance, which sometimes causes metabolic
disturbances, such as ketosis. Subclinical ketosis (SCK) is defined as an
increase in the β-hydroxybutyrate (BHB) concentration to ≥ 1.2 mmol/l in the
blood. According to a recent study, a value of ≥ 0.7 mmol/l of non-esterified
fatty acids (NEFA) in the blood indicates the potential development of the poor
metabolic adaption syndrome (PMAS). With a herd prevalence of 21 %, and an
incidence of approximately 40 % within the first 2 weeks after calving, SCK is a
relevant herd health problem. The milk yield decreases in the first 2 weeks
postpartum by 3–5.3 kg/d for each ketotic cow, and the total milk reduction
through the whole lactation period of 305 days averages 112 kg (SD 89 kg).
Although the cow does not display any clinical signs of ketosis at this stage,
the risk of developing associated production diseases like retained placenta,
metritis, displaced abomasum, lameness and clinical ketosis increases and the
expected performance in terms of milk production will decrease. The herd health
status deteriorates and the risk for early culling increases. Another impact
factor is the financial aspect, which includes costs for early death, reduced
milk production, reproduction losses, and associated production diseases. In the
literature, the calculated costs per SCK case vary between $ 78 and $ 289. The
gold standard diagnostic test for SCK is the photometric measurement of BHB in
blood. This method is accurate, but results are delayed due to the required
laboratory analysis. There are also some rapid cow-side tests, i. e. urine or
milk strip tests available to identify ketotic cows. The common disadvantage of
these methods is that they are not suitable for herd health monitoring because
of the need to collect samples from each cow manually and the high rates of
false negative results. However, Fourier transform infrared spectroscopy is
suitable for herd health monitoring. It is already being used for the analysis
of milk composition. This inexpensive, rapid and simple technique has a
specificity of 83.8 % and a sensitivity of 82.4 %. Therefore, FTIR is an early
and easy method for detecting ketotic cows, that could help reduce financial and
performance losses associated with ketosis.