Abstract
Gastrointestinal nematodes are an important cause of reduced performance in cattle. Previous studies in Europe showed that after anthelmintic treatment an average gain in milk production of around 1 kg per day/cow can be expected. However, (1) these studies have mainly evaluated group-based anthelmintic treatments during the grazing season or at housing and (2) little is known about parameters affecting variations in the treatment response amongst cows. A better knowledge of such parameters could help to select animals that benefit most from treatment and thus lead to a more rational use of anthelmintics. Therefore, a randomized, non-blinded, controlled clinical trial was performed on 11 commercial dairy farms (477 animals) in Belgium, aiming (1) to study the effect of eprinomectin treatment at calving on milk production and (2) to investigate whether the milk yield response was related to non-invasive animal parameters such that these could be used to inform targeted selective treatment decisions. Analyses show that eprinomectin treatment around calving resulted in an average (± standard error) increase of 0.97 (±0.41) kg in daily milk yield that was followed up over 274 days on average. Milk yield responses were higher in multiparous compared to primiparous cows and in cows with a high (4th quartile) anti-O. ostertagi antibody level in a milk sample from the previous lactation. Nonetheless, high responses were also seen in animals with a low (1st quartile) anti-O. ostertagi antibody level. In addition, positive treatment responses were associated with higher faecal egg counts and a moderate body condition score at calving (2nd quartile). In conclusion, this study provides novel insights into the production response after anthelmintic treatment at calving and factors which influence this. The data could be used to support the development of evidence-based targeted selective anthelmintic treatment strategies in dairy cattle.
Highlights
Gastrointestinal nematodes are an important cause of reduced performance in cattle
The following criteria were applied for the selection of farms: (1) cows had previous access to pasture and were naturally infected with gastrointestinal nematodes, (2) the last treatment of the cows against Gastrointestinal nematodes (GI) nematodes had been performed ≥6 months before the experimental treatment and (3) participation in the milk production registration program of CRV (Arnhem, The Netherlands) to enable standardized data collection
Herd characteristics and treatment allocation Analysis of the effect of treatment on the anti-O. ostertagi antibody levels was based on data obtained from 498 animals present in the participating herds
Summary
Gastrointestinal nematodes are an important cause of reduced performance in cattle. Previous studies in Europe showed that after anthelmintic treatment an average gain in milk production of around 1 kg per day/ cow can be expected. A randomized, non-blinded, controlled clinical trial was performed on 11 commercial dairy farms (477 animals) in Belgium, aiming (1) to study the effect of eprinomectin treatment at calving on milk production and (2) to investigate whether the milk yield response was related to non-invasive animal parameters such that these could be used to inform targeted selective treatment decisions. A review of studies on the effect of anthelmintic treatment on milk production from 2000 onwards reported an average milk yield response of 1 kg/cow per day [1]. In Europe, all recent clinical studies, evaluating the effect of anthelmintic treatment on milk production can be considered as TT, as they target whole herds, and have been restricted to mid-season or housing treatments [4,5,6,7,8]. Studies assessing the effect of anthelmintic treatment around calving have been carried out in Canada [10,11,12] and New Zealand [13], but significant differences in climate and farm management practices may result in different parasite epidemiology and different production effects when compared to European circumstances
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