Responses in milk production to the control of gastrointestinal nematode and paramphistome parasites in dairy cattle

Objective To determine the effect of treating naturally acquired gastrointestinal nematode and paramphistome infections on milk production in dairy cattle. Design A field trial. Animals One thousand two hundred and thirty nine dairy cows. Procedure Cows were either not treated or treated with 4.5 mg/kg oxfendazole, 16.6 mg/kg oxyclozanide or 4.5 mg/kg oxfendazole and 16.6 mg/kg oxyclozanide in March, May and August. Results A significant increase in milk production, averaging 0.4 L (SE 0.2) per day, was seen when dairy cows infected with gastrointestinal nematodes and paramphistomes were treated with oxfendazole or oxfendazole and oxyclozanide in March, May and August. Cows treated with oxyclozanide alone at these times produced no more milk than untreated cows. Faecal egg counts confirmed that oxyclozanide treatment reduced paramphistome populations and oxfendazole treatment reduced nematode populations in cows over the 7-month monitoring period. Conclusion When dairy cows infested with gastrointestinal nematodes and paramphistomes were treated with oxfendazole alone or oxfendazole and oxyclozanide in March, May and August milk production increased.