Given the economic impact of gastrointestinal nematode infection on livestock farming worldwide, and increasing anthelmintic resistance, it is imperative to develop practical, efficient and sustainable control strategies. Targeted selective treatment (TST), whereby anthelmintic treatments are administered to animals individually, based on selection criteria such as weight gain, has been shown to successfully maintain animal productivity whilst reducing the selection pressure for anthelmintic resistance and the economic cost of treatment in experimental and commercial settings. Despite the benefits of the TST approach, the equipment and time required to monitor animals individually make this strategy unsuitable for some farming enterprises. The sentinel group approach aims to maintain the benefits observed using TST whilst reducing these requirements. The study involved two experiments, each following a group of 80 lambs through their first grazing season. Anthelmintic treatment of the whole group was determined by monitoring the weight gain of identified sentinel lambs within it every 2 weeks: when 40% of the sentinel lambs failed to reach their weight gain targets, the whole group was treated. The sentinel lambs consisted of 45% of the group (n = 36) in experiment one and 20% (n = 16) in experiment two. A control group of 20 lambs was co-grazed with the main group during both experiments; in experiment one, the sentinel approach was compared with a TST approach, in which control lambs were treated on an individual basis in response to weight gain. In experiment two, the sentinel approach was compared with conventional prophylaxis, where all lambs in the control group were treated at strategic time points throughout the season (= strategic prophylactic treatment). The sentinel lambs were found to be representative of overall group performance regardless of the proportion of sentinels within the group: they recorded similar growth rates and reached weight gain targets simultaneously at each time point and overall. Live-weight gain was also similar between sentinel and control animals in both experiments. The findings of the current study suggest that monitoring sentinel lambs comprising 20% of a group of grazing lambs is sufficient to determine the need for anthelmintic treatment within the whole group, and that this approach maintains production in line with conventional or TST treatment regimes.
Bibliographical noteFunding Information:
The authors would like to thank Scott Roger, the Moredun Bioservices team and Dr. Dave Bartley, Alex Fyfe, Ed Marr, Michelle Munro, Sara-Jane Ponting for their help with sample collection, Mintu Nath for his input into early discussions of the proportion of lambs to be monitored and Paul Torgerson for helpful advice on the simulations. This research was funded by the EU FP7 project GLOWORM (Grant Agreement No. 288975CP-TP-KBBE.2011.1.3-04) and the Scottish Government's Rural Affairs Food and Environment Strategic Research (RESAS) programme. The Moredun Research Institute is one of the Scottish Government's major research providers under the collective of the Scottish Environment, Food and Agriculture Research Institutes (SEFARI).
This research was funded by the EU FP7 project GLOWORM (Grant Agreement No. 288975CP-TP-KBBE.2011.1.3-04 ) and the Scottish Government’s Rural Affairs Food and Environment Strategic Research (RESAS) programme. The Moredun Research Institute is one of the Scottish Government’s major research providers under the collective of the Scottish Environment, Food and Agriculture Research Institutes (SEFARI).
© 2021 The Authors
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- Gastrointestinal nematodes
- Production indicators
- Smart livestock farming
- Targeted treatment
ASJC Scopus subject areas
- Animal Science and Zoology