Cross-sectional serological survey on gastrointestinal and lung nematode infections in first and second-year replacement stock in The Netherlands: relation with management practices and use of anthelmintics

A cross-sectional survey was carried out on 86 farms randomly distributed i n The Netherlands. After housing following the first and the second grazing season (FGS and SGS) serum samples were collected to determine IgG levels against Cooperia oncophora and Dictyocaulus viviparus, and the pepsinogen c ontent. A questionnaire was used to inquire on grazing management practices and the use of anthelmintic drugs. On 80.7 and 60.2% of the farms FGS and SGS animals, respectively, were treated at least once with an anthelmintic drug. The percentage for the SGS animals indicates that the use of anthelmi ntic drugs in those animals has increased enormously over the last 10-15 ye ars. Generally, parasitic nematode control in the FGS is good on most farms , but it can be characterised as being overprotective. There is a tendency that if anthelmintic drugs are used in the FGS they also are used more ofte n in the SGS, On 12 farms (14%), no anthelmintic drugs were given in the FG S and the SGS. These farms did not differ from the others with respect to m anagement practices in any obvious way. The serological results were in gen eral very low, indicating low levels of exposure to gastrointestinal nemato de infection in both FGS and SGS animals. This was not surprising in view o f the good to high level of nematode control practices reported by the farm ers. Although not statistically significant, a consistent result was that s erological results for the SGS animals were more often positive or on avera ge higher on those farms where FGS parasite control tended to be excessive. For D. viviparus, a prevalence rate of 41% positive farms was found. Follo wing comparison with previous data, it is speculated that lungworm (sero-)p revalence in replacement stock may be declining as a result of continuing h igh levels of parasite control in replacement stock. it is concluded that t he results confirm previous surveys, lending support to the conclusion that parasitic nematode control on Dutch dairy farms, certainly in FGS calves, is good but tends to be overprotective. (C) 2000 Elsevier Science B.V. All rights reserved.