Market stress-associated changes in serum complement activity in feeder calves.

Area of Science:

• Veterinary Immunology
• Animal Science
• Bovine Health

Background:

• Feeder calf handling protocols in the southeastern United States involve significant stressors.
• Hemolytic complement (C) is a crucial component of the innate immune system in cattle.
• Understanding complement levels is vital for assessing calf health and stress responses.

Purpose of the Study:

• To analyze classical hemolytic complement (C) concentrations in feeder calves throughout typical market handling.
• To evaluate the impact of market stresses on calf immune status.
• To identify factors influencing complement levels, such as sex, health status, and origin.

Main Methods:

• Serum C concentrations (CH50 units) were measured in 100 calves over 4 years.
• Sampling occurred at the farm of origin, auction market, feedyard arrival, and during the first 4 weeks in the feedyard.
• Statistical analysis compared C levels based on sex, health status, farm origin, and vaccination history.

Main Results:

• Complement levels were lowest at the farm of origin and peaked upon arrival at the auction market.
• Serum C concentrations decreased significantly following auction market exposure, transport, and initial feedyard period.
• Calf C concentrations recovered within 21–28 days in the feedyard.
• Steers generally had lower C levels than heifers; morbid calves had lower C than healthy calves.
• Significant variations in C levels were observed between calves from different farms of origin.

Conclusions:

• Market handling and associated stresses temporarily suppress calf hemolytic complement levels.
• Calves demonstrate immune recovery within a month of feedyard arrival.
• Sex and health status are significant factors influencing complement levels during the marketing process.
• Farm of origin impacts calf immune status, highlighting the need for origin-specific health management.