Association between culling reasons and lactation curve components in Holstein cows

Area of Science:

• Dairy Science
• Animal Production
• Veterinary Epidemiology

Background:

• Lactation curves model milk production, guiding dairy farm management.
• Culling decisions significantly affect dairy farm economics and animal welfare.
• Lactation curve components (LCC) in culled versus retained Holstein cows remain understudied.

Purpose of the Study:

• To investigate and compare the LCC of culled Holstein cows with those retained in the same herd.
• To identify how specific culling reasons correlate with distinct lactation curve patterns.
• To provide data for improved dairy herd management strategies.

Main Methods:

• Utilized 27,297 complete lactation records from Holstein cows categorized as retained or culled.
• Employed the incomplete gamma function to estimate LCC parameters (initial milk yield, peak yield, rates of increase/decline, time to peak, persistency).
• Applied the general linear model to analyze the impact of culling status on LCC.

Main Results:

• Cows culled for reproductive disorders had similar LCC to retained cows but longer lactation lengths.
• Most culled cows (excluding reproductive issues) showed decreased lactation length, faster milk decline, and lower persistency.
• Cows culled for metabolic disorders had higher initial and peak milk yields compared to retained cows.

Conclusions:

• Linking culling causes to milk production trends aids in early risk identification for dairy farmers.
• Monitoring milk decline onset and adapting management can help retain healthier, high-value cows.
• This approach can reduce costs, enhance milk output, and improve overall dairy herd welfare.