Final answer:
Dairy calves should be wormed every one or two months to prevent and control helminth infections.
Step-by-step explanation:
Dairy calves should be wormed every one or two months to prevent and control helminth infections. These infections can occur when calves ingest vegetation contaminated by eggs or gravid proglottids, or through direct contact with infected animals. The preferred treatment for helminth infections in calves is ivermectin, with albendazole as a secondary option.