Comparing body condition score and FAMACHA© 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© 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© scores and BCS of adult ewes were recorded monthly. Ewes with FAMACHA© ≥ 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© ≥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.