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Gastrointestinal (GI) nematodes are the most common nematodes in cattle; they occur worldwide and especially in temperate countries. Cooperia oncophora and Ostertagia ostertagi are the most common species which colonise the small intestines and abomasum of cattle respectively. In the last decades anthelminthic resistance started to become an increasing problem in cattle farming industry. In Europe, New Zealand and South America (Molento et al., 2011, Demeler et al., 2009, Pomroy, 2006, Chartier et al., 2001) reduced efficacy of anthelmintics in cattle herds has already been described. For this reason, strategic herd treatment should be replaced by alternative control strategies. In the present work two studies were conducted. The first study evaluated the effect of alternative treatment programs to control GI nematodes infection in first season grazing beef calves. The second study aimed at the investigation of BZ resistance by using the faecal egg cunt reduction test (FECRT) and by applying molecular techniques for SNP detection in C. oncophora and O. ostertagi.
The first study was conducted in three beef cattle farms in the federal state of Brandenburg, Germany. The calves were grouped into four groups: Targeted Treatment (TT), Targeted Selective Treatment (TST), Positive Control (strategic regular treatment) and Negative Control (no treatment). Sampling was performed during two years: two farms were visited in 2013 from May to October and one farm was investigated in 2014 between June and November. Daily weight gain (DWG) and body condition score (BCS) according to (Edmonson et al., 1989) were determined monthly and faecal samples were collected also at each visit. Faecal samples were analysed using a modified McMaster method on the first two farms and the Mini FLOTAC method on the third farm. The carcass weight, fat and muscles thickness and meat classes were obtained from the slaughter house. For the treatment Valbazen® SUSPENSION (containing albendazole) was used. The anthelmintic treatment decision criteria were either a combination of a high FEC (>100) and decrease in DWG (<1.125 kgperday) or a high FEC in combination with a decreasing BCS. A strong positive correlation between the body weight and the BCS was found. The infection level on all farms was low with mean FECs below 100 and individual FECs rarely exceeding 200. The only mild infection didn’t affect the productivity of the calves in the untreated control group but the treatment had a significant effect on the FECs in all other groups. The statistical analysis of the data revealed that there was no significant difference between the treatment groups in the DWG, BCS or carcass weight. Allocation to a particular treatment group did not affect the productivity or performance of the animals. The PC group which was treated routinely every month did not achieve a better live weight or carcass weight but generated significantly higher costs in anthelmintic usage.
The occurrence of BZ resistance was investigated using the FECRT on 11 farms in Brandenburg, Germany. Faecal samples were collected pre and post treatment with albendazole and sampling was undertaken between July and October 2014. The statistical analysis revealed that only one farm shows a reduced efficacy with a reduction percentage of 76%. However, again the overall FECs were very low making the analysis very difficult. Additionally to those farms analysed by the FECRT farmers in Germany, Ireland and Belgium were asked to send in faecal samples from their herds before treatment. Larval cultures were performed and L3s subjected to DNA extraction and subsequent PCR analysis. Genus differentiation was performed revealing relatively high number of farms with only single infections (either Cooperia or Ostertagia) and only a moderate number of farms in Ireland and Germany with mixed infections. However, since the number of larvae obtained from the cultures and available for DNA extraction varied significantly between farms (100-50,000 L3) these results can also be due to the low numbers of L3s in some samples. Pyrosequencing targeting the SNPs at codon 167, 198 and 200 of the ß-tubulin isotype 1 gene could only be performed for a small subset of the samples and due to time limitations also only data from a single run was available. The preliminary results obtained show no significant increase of the BZ resistance associated SNPs in any species in any of the samples. This is in agreement with previous reports that, unlike in South America or Australia/New Zealand, BZ resistance does not seem to be a problem in Europe in cattle nematode populations yet.
Overall, the findings of the present work show that the productivity in beef calves could be maintained by applying alternative treatment strategies such as TT or TST and an overall very low use of anthelmintics. This can lead to economic benefits through saving money and delaying the onset of resistance development. Particularly on organic based farms where strategic treatment is not possible, the implementation of TT or TST can be of benefit.