Viability of the Happy Factor TM targeted selective treatment approach on several sheep farms in Scotland

D McBean, M Nath, NR Lambe, C Morgan-Davies, F Kenyon

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The aim of this study was to examine the use of Happy Factor TM weight based targeted selective treatment(TST) on several commercial farms in Scotland in combination with findings from a long term trial ona research farm to assess the potential for TST use in varying farming operations as an alternative tothe current regimen of whole flock treatment. Lambs on each farm were regularly weighed and climaticconditions and pasture availability measured for inclusion into the Happy FactorTMmodel to calculateweight targets. Half of the lambs were allocated to TST treatment and any failing to reach the weighttarget was treated with the anthelmintic of choice on that farm, while the remaining half of each flock wastreated with anthelmintic as per normal practice on that farm (routine treatment, RT). The research farm(farm 1) hosted a long term trial using four anthelmintic treatment regimes over 6 years, and data fromtwo regimes are presented here, alongside findings from three further farms: two commercial enterprises(farms 2 and 3) and a research farm operating as a commercial analogue with two breeds (farms 4aand 4b). The effect of TST strategy on lamb productivity and the number of anthelmintic treatmentswas investigated. There was no evidence (p > 0.300) that mean bodyweight or growth rate was differentbetween TST and RT groups on any of the farms and 95% confidence intervals of TST and RT groupsgenerally suggested that TST had negligible unfavourable effects on the average growth of lambs for mostof the farms. Growth rates ranged from 97.39 to 189.16 g/day reflecting the varied nature of the farms.All commercial farms used significantly less (1.34 RT versus 1.14 TST treatments per animal, p < 0.05)anthelmintic in lambs following TST, with a reduction from 1, 1, 1.03 and 1.14 to 0.77, 0.57, 0.82 and 0.81in the number of treatments per animal for farms 2, 3, 4a and 4b respectively. This study suggests that TST is a viable means of controlling parasitic disease without incurring production losses.© 2016 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)22 - 30
Number of pages9
JournalVeterinary Parasitology
Publication statusFirst published - 2016

Bibliographical note



  • Gastrointestinal nematodes
  • Refugia
  • Sheep
  • Targeted selective treatment


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