Comparing body condition score and FAMACHA(C) to identify hair-sheep ewes with high faecal egg counts of gastrointestinal nematodes in farms under hot tropical conditions

Data from a targeted selective treatment (TST) survey in three sheep farms was used to compare body condition scores (BCS) <= 2 and FAMACHA(C) scores >= 4 or >= 3 as criteria to identify ewes with >= 750 eggs per gram of faeces (EPG), and to confirm whether that EPG threshold allowed maintaining a large proportion of animals with no anthelmintic (AH) treatment. The survey included monthly data from all grazing adult ewes in three commercial farms. Farms 1 and 3 were surveyed for 11 months, and Farm 2 for 6 months, with a total of 7342 events recorded. Mean monthly population consisted of 330 ewes (Farm 1), 129 ewes (Farm 2) and 265 ewes (Farm 3). The FAMACHA(C) scores and BCS of adult ewes were recorded monthly. Ewes with FAMACHA(C) >= 4 or BCS <= 2 were faecal sampled to determine faecal egg counts (FEC) (2788 events). Ewes with >= 750 EPG were treated with an AH (658 events). The TST survey showed that BCS <= 2 was the best criteria to find ewes with FEC >= 750 EPG, with 1.1% false negatives. Meanwhile, FAMACHA(C) >= 4 or >= 3 failed to identify half of the events with >= 750 EPG (50-55% false negatives). Thus, the TST scheme could focus on screening ewes with BCS <= 2, and the FEC of those animals can avoid unnecessary AH treatments. The TST scheme was easier to implement at the farm with largest ratio of ewes with BCS > 2, as fewer ewes were sampled and treated, compared to farms where many ewes had BCS <= 2. In the surveyed farms a threshold of >= 750 EPG resulted in 63.5% of all ewes maintained with no AH treatment for the duration of the survey.