Risk factors for lungworm-associated milk yield losses in grazing dairy cattle

Area of Science:

• Veterinary Parasitology
• Dairy Science
• Animal Husbandry

Background:

• Bovine parasitic bronchitis, caused by Dictyocaulus viviparus, leads to substantial economic losses in dairy cattle.
• Limited research exists on herd management risk factors for lungworm infections and associated production losses.

Purpose of the Study:

• To assess the impact of lungworm infections on dairy cow productivity.
• To identify herd management risk factors for Dictyocaulus viviparus infections in grazing cattle.

Main Methods:

• A recombinant Major Sperm Protein (MSP)-based ELISA was used to detect D. viviparus antibodies in bulk tank milk (BTM) from 717 and 634 farms over two grazing seasons (2018-2019).
• Associations between milk antibody levels and production data (milk yield, fat, protein) were analyzed.
• Herd management risk factors were identified through a questionnaire survey.

Main Results:

• A significant negative association was found between elevated BTM antibody levels (two consecutive positive tests in 2019) and milk yield (-1.74 kg/cow/day).
• Purchasing new animals (OR=2.68) and the proportion of the grazing season with anthelmintic treatment were risk factors for milk yield loss.
• Mowing at least 50% of pastures was associated with reduced milk yield losses (OR=0.57).

Conclusions:

• Repeated BTM sampling with ELISA can identify dairy herds experiencing significant production losses due to lungworm infections.
• Adjusting herd management practices, such as controlling new animal introductions and optimizing grazing management, may mitigate economic losses from lungworm.
• The study highlights the potential of ELISA for early detection and management of lungworm in dairy herds.