A Sustainable Strategy for Gastrointestinal Nematode Control in Sheep

Gastrointestinal nematodes (GIN) represent a major constraint to sheep production, and sustainable alternatives to routine anthelmintic use are increasingly required. This study compared two parasite control strategies in Zerasca sheep: routine albendazole treatment administered twice yearly (T) and a long-term non-chemical approach based on rotational grazing (relocation to a new pasture when grass height fell below 10 cm) combined with quarterly veterinary monitoring (NT). Twenty-four adult ewes (n = 12 per group) were monitored over an eight-month period. Mean faecal egg counts (EPG) differed significantly between groups (T: 210 ± 78; NT: 529 ± 89; p = 0.0007). In group T, EPG values decreased markedly 7 days after treatment but increased again by 150 days, resulting in no persistent differences between groups over time. Despite higher parasite burdens, NT sheep showed significantly higher body condition scores compared with treated animals (3.00 ± 0.61 vs. 2.51 ± 0.53; p = 0.0014). Haematological parameters were largely comparable between groups, although mild reductions in RBC, HGB, and HCT were observed in both. Treated sheep exhibited higher AST activity (p < 0.0001) and transient increases in ALT and BUN following treatment. Hair cortisol concentrations did not differ significantly between groups. Overall, these findings suggest that a non-chemical parasite management strategy, when combined with controlled grazing and veterinary monitoring, may maintain acceptable parasite levels while supporting body condition and stable welfare indicators, potentially reducing reliance on routine anthelmintic treatments.