Association between Dictyocaulus viviparus status and milk production parameters in Dutch dairy herds

The objective of this study was to estimate the association between Dictyocaulus viviparus bulk tank milk (BTM) test results and milk production and milk composition parameters in adult Dutch dairy cattle herds. Bulk tank milk samples were collected in August and November 2013, and ELISA tests were performed. Two hundred BTM positive (BTM+) and 200 BTM negative (BTM-) herds were selected based on their BTM test result of November 2013, obtained from a list of farms that participated in the Dutch GD Animal Health voluntary monitoring program for controlling nematode infections. The relationship between D. viviparus BTM status and 3 production parameters (milk production, milk fat %, and milk protein %) in summer (June to August 2013) and autumn (September and October 2013) was investigated using generalized linear mixed models. Production data were available for 126 BTM- herds and 109 BTM+ herds. Results showed that a positive D. viviparus status was associated with decreased milk production (June: -1.01, July: -1.19, August: -1.68, September and October: -1.33 kg/cow per d). Milk fat percentage was 0.14% and 0.08% lower during summer and autumn, respectively, in BTM+ herds. No significant association was demonstrated between a positive BTM test result and milk protein percentage. Because a strong correlation was present between the BTM status for D. viviparus and that for Ostertagia ostertagi, these losses cannot be attributed to one of the two parasites. However, it is clear that these parasite infections have a considerable effect on production.