Targeted treatment strategies for the control of gastrointestinal nematodes in a goat flock with anthelmintic resistant worm populations and poor nutrition

Combined targeted selective treatment schemes using FAMACHA©, body condition score (BCS), and faecal egg counts (FEC) can reduce the number of anthelmintic (AH) treatments per year in goat farms, which can slow down the selection of AH-resistant worm populations. Supplementary feeding can further reduce the FEC of goats at the farm level. A 19-month survey was implemented to (i) identify the number of times that goats crossed the thresholds of FAMACHA©, BCS, and FEC, (ii) identify the monthly FEC reductions of goats treated with AH in the targeted scheme, and (iii) identify the effect of a supplementation scheme on the goats’ FEC. The survey was performed at a goat farm in tropical México. Goats grazed natural vegetation four h/day and received concentrate feed daily (14% crude protein, 150 g each). Each month, goats (n = 88) were examined, and those with FAMACHA© ≥ 4, BCS ≤ 2, and FEC ≥ 750 eggs per gram of faeces (EPG) were identified (Day 0). From September 2018 to September 2019, goats crossing the FEC threshold (events) were allocated to two different groups distributed according to FEC values: deworming group (DG; n = 71 events) and supplemented group (SG; n = 72 events). From October 2019, all the goats were assigned only to the DG (n = 31 events) due to management problems in the study farm. The DG goats were individually weighed and treated with levamisole (LEV, 12 mg/kg body weight (BW), subcutaneous (sc)) and their normal diet. From November 2019 to March 2020, the DG goats were treated with LEV and benzimidazole (BZ, 7 mg/kg BW, sc). The SG goats were individually supplemented with an additional 300 g of concentrate feed for ten days. From the 88 goats surveyed, 70.5% crossed the FAMACHA©/BCS thresholds, with goats sampled 1–7 times. From the 369 sampled events, only 56% had ≥ 750 EPG. The FEC reduction of DG goats treated with LEV ranged from 46.7% to 96.1%, and with LEV+BZ combination was 100%. The FEC reduction in the SG goats ranged from 27.7% to 95.5%. Supplementation of SG goats had a positive impact on most goats and helped to limit the number of dewormed goats. To be effective, the supplement must be an addition to the normal diet.