# A Sustainable Strategy for Gastrointestinal Nematode Control in Sheep

## TL;DR

This study shows that non-chemical methods like rotational grazing can effectively manage parasites in sheep without harming their health or the environment.

## Contribution

The study demonstrates a viable non-chemical alternative to routine anthelmintic treatments for sustainable parasite control in sheep.

## Key findings

- Non-chemically managed sheep had higher body condition scores despite higher parasite burdens.
- Treated sheep showed temporary reductions in parasite egg counts but returned to similar levels within five months.
- Non-chemical management did not affect long-term stress indicators or welfare.

## Abstract

Sustainable parasite control in sheep must reconcile environmental protection with animal health and welfare. This study compared two gastrointestinal nematode management strategies in an endangered local sheep breed: routine anthelmintic treatments versus a long-term non-chemical approach based on rotational grazing and veterinary monitoring. Although treated animals showed a temporary reduction in parasite egg counts shortly after deworming, this effect was short-lived and disappeared within five months. Sheep managed without routine anthelmintics maintained moderate parasite burdens without clinical disease and displayed significantly better body condition scores throughout the study. Haematological parameters were largely comparable between groups, while treated animals showed higher liver enzyme activity and transient metabolic alterations following drug administration. Long-term stress indicators, assessed by hair cortisol, did not differ between strategies, suggesting similar welfare levels. Overall, the results indicate that non-chemical parasite management, when combined with careful monitoring, can maintain animal health and welfare while reducing drug use and potential environmental contamination. This approach represents a viable and sustainable alternative to routine anthelmintic treatments in extensive sheep farming systems.

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.