Controlling nematodes in dairy calves using targeted selective treatments

Area of Science:

• Veterinary Parasitology
• Animal Science
• Sustainable Agriculture

Background:

• Anthelmintic resistance in cattle nematodes necessitates alternative control strategies.
• Targeted selective treatments (TST) offer a potential solution by treating only individual animals.
• Controlling gastrointestinal nematodes and lungworm in calves requires effective and sustainable methods.

Purpose of the Study:

• To evaluate the efficacy of a TST approach for controlling gastrointestinal nematodes and lungworm in dairy calves during their first grazing season (FGS).
• To assess the impact of TST on anthelmintic use, parasite burdens (faecal egg count and lungworm larvae), plasma pepsinogen concentration, and live weight gain.
• To determine the feasibility of maintaining performance with reduced anthelmintic exposure.

Main Methods:

• Ninety-six dairy calves were randomized into Control (routine treatment) and TST groups.
• TST calves received ivermectin based on specific thresholds: lungworm larvae detection or elevated plasma pepsinogen concentration (PP) with high faecal egg count (FEC).
• Calves were grazed rotationally and monitored every three weeks for weight, blood (for PP), and faecal samples (for FEC and lungworm larvae).

Main Results:

• A 50% reduction in anthelmintic use was observed in the TST group compared to the Control group.
• Both FEC and PP were significantly higher in TST calves, indicating increased parasite challenge.
• No significant difference in average daily live weight gain was found between the Control (0.50 kg/day) and TST (0.47 kg/day) groups.
• Clinical signs of lungworm infection were noted in TST calves.

Conclusions:

• TST can significantly reduce anthelmintic usage in dairy calves during their first grazing season without compromising live weight gain.
• Farmers implementing TST must remain vigilant for lungworm infections, as this parasite can pose a challenge.
• Future TST strategies for FGS calves should consider the specific role and impact of lungworm as a pathogen.