Abstract Much research has gone into developing a sustainable management tool for haemonchosis, namely the FAMACHA© system, which has been validated by numerous studies worldwide. However, the financial implications on production of implementing this system have not been fully investigated in sheep previously. A trial was conducted on a farm comprising a flock of approximately 300 Mutton Merinos on which the FAMACHA© system was in use. Seventy five maiden and multiparous ewes were randomly allocated to the following three trial groups: (i) FAMACHA© in which ewes judged to be in categories 4 or 5 were dosed with levamisole HCl 2.5% (Nemasol NF, Intervet); (ii) Conventionally dosed in which all ewes were dosed every six weeks with levamisole HCl 2.5% (Nemasol NF, Intervet); (iii) Suppressively dosed in which all ewes were injected every six weeks with moxydectin 1% m/v (Cydectin, Bayer AH). There were no significant differences in body weight gains, FAMACHA© and body condition scores amongst the three treatment regimens for ewes that did not conceive. For those that became pregnant during the trial there was a significant difference when analysed by calendar date but not when analysed by reproductive stage. There were also no significant differences between trial groups in lamb birth weight and, after slow growers had been sold, the average daily gain of the lambs born to ewes in the trial. The cost of anthelmintics was considerably lower for the FAMACHA© group. In conclusion there were no significant differences in selected production parameters when using the FAMACHA© system as opposed to other methods of anthelmintic use in a Mutton Merino flock in a semi-intensive farming system and that the gestation status should be taken into account when measuring these parameters in future studies.