Infections with the liver fluke Fasciola hepatica remain a serious problem in dairy herds causing significant production losses. In sheep, a strong relationship between F. hepatica
infections and an increase in serum
ketone bodies due to reduced feed intake and liver damage was demonstrated. We hypothesized that F. hepatica
infections might contribute to an increase in milk
ketone bodies in dairy herds. Thus, the objective of the study was to estimate the association between F. hepatica bulk tank milk (BTM)
antibodies and milk production parameters (milk yield,
milk protein, fat yield), somatic cell count (SCC) and the milk
ketone bodies ß-hydroxybutyrate (BHB) and
acetone, inferred from Fourier transform infrared (FTIR) spectrometry, via linear mixed model analysis. A further aim was to follow up the F. hepatica seroprevalence in dairy herds in the northern German region East Frisia. We collected BTM samples between October and December from 1022 herds in 2017 and 1318 herds in 2018. Overall, 33.1 % of the herds tested positive in 2017 and 37.0 % in 2018, showing decreased F. hepatica seroprevalences compared to prior seroprevalence studies in the same region in 2010, 2008 and 2006 (> 45 % positive herds). We estimated a significant negative association (P < 0.001) between herd F. hepatica
infection category and average milk yield with a loss of -1.62 kg per cow per day in strongly infected herds compared to BTM ELISA negative herds. Moreover, F. hepatica
infection category had a significant effect on herd average
milk protein and fat yield (P < 0.001), showing a decrease of 0.06 kg for both parameters from BTM ELISA negative herds to strongly infected herds. No significant association with milk SCC was found (P = 0.664). Regarding
ketone bodies, we estimated significant higher average BHB values in strongly infected herds compared to the other three
infection categories in the model analysis (P = 0.002). The association between F. hepatica
infection category and
acetone values was not significant (P = 0.079). Besides primary
ketosis, fasciolosis should be considered as differential diagnosis in dairy herds with increased BHB values.