Culling Reasons in Industrial Dairy Farms of Western Tehran Province, Iran: A Herd‐Size Stratified Analysis and Management Implications

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Abstract
This study investigated culling reasons in 27 industrial and semiindustrial dairy farms (15,907 cattle) in western Tehran Province, Iran, using records from 2010–2014 (with detailed analysis for 2012–2014). Herds were stratified by size: 20–100, 101–200, 201–500, and > 500 head. Milk yield increased with herd size (6955 to 8750 kg), while fat (4.06% to 3.86%) and protein (3.28% to 3.20%) decreased, showing strong negative correlations with yield (−0.79 to −0.89 for fat; −0.77 to −0.88 for protein) and positive correlations between fat and protein (0.91–0.94). Involuntary culling predominated (70%–76%), with reproductive disorders (15%–20%), mastitis (13%–15%), lameness (15%), and low milk yield as primary causes. Larger herds exhibited higher involuntary culling for health‐related issues, consistent with findings that high milk yield is associated with deteriorated cow health and fertility. Herds of 201–500 head demonstrated optimal balance between productivity (mean 32 kg/day, 3.1% fat) and lower culling rates for mastitis, udder disorders, and lameness compared to larger herds. These findings indicate that targeted management and breeding strategies—including fertility‐focused selection and proactive health monitoring—could reduce involuntary culling by 10%–15% and enhance herd sustainability in Tehran’s dairy industry.

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