Impact of the rumen fluke Calicophoron daubneyi on milk production parameters, β-hydroxybutyrate, fertility and feces consistency in southern German dairy cows.

The infection of cattle with the rumen fluke Calicophoron daubneyi has been detected with increasing frequency in Europe in recent decades. The question of the importance of this parasitic infection for milk production has come to the fore. While the influence on beef cattle has already been investigated in a few studies with contradictory results, there is hardly any knowledge about an influence on milk yield and fertility. Therefore, in a case control field study, we aimed to determine the monthly excretion of C. daubneyi eggs in the feces of dual-purpose dairy cows on two farms in southern Germany over a period of one year, and to compare milk yield and fertility parameters between infected and non-infected cows within the herds. For this purpose, the cows were divided into groups depending on egg excretion (1 = negative; 2 = rumen fluke-positive; 3 = rumen fluke- and liver fluke-positive). To be able to investigate seasonal influences, the data was analysed in three time-intervals (entire study period, summer half-year, winter half-year). A total of 117 cows from the two farms were examined in this study. The in-herd-prevalence for rumen fluke was 57.0 % and 64.0 %, respectively. The median egg excretion was low in both farms (< 6 epg), the maximum excretion reached 92.3 epg. Cows coinfected with F. hepatica showed the highest rumen fluke egg excretion rate. Calicophoron daubneyi infection had no significant effect on milk production parameters (milk yield, milk fat, milk protein, and somatic cell count). Remarkably, all infected cows showed higher values of milk fat content than non-infected cows. The metabolic parameter β-hydroxybutyrate (BHB), determined using Fourier-transform mid-infrared (FT-MIR) spectroscopy, was within the normal range on both farms and did not differ between infected and uninfected cows. The fertility parameters (CTFS - calving to first service, CIV - calving interval, SFI - success in first insemination, and 56-NRR - 56-day non-return rate) tended to be worse in C. daubneyi infected cows but without significant difference to non-infected cows. No influence on the consistency of feces was observed in rumen fluke-infected cows. In summary, this study showed that low-level infections with C. daubneyi had no influence on milk yield or metabolic status in dual-purpose dairy cows, while C. daubneyi infected cows tended to perform unfavourable in some parameters compared to uninfected cows.