# Longevity and Culling Reasons in Dairy Herds in Southern Brazil

## TL;DR

This study examines why cows are removed from dairy farms in Southern Brazil and how long they stay in the herd, finding that health issues and farm size significantly influence culling rates.

## Contribution

The study provides new insights into culling patterns and longevity in Southern Brazilian dairy herds, linking farm management practices to animal welfare and productivity.

## Key findings

- Health issues like reproductive failure and udder infections are the main reasons for culling.
- Larger and more productive farms have higher culling rates.
- Older cows with more calvings are more likely to be culled, but this does not always improve productivity.

## Abstract

Culling, or the removal of cows from the herd, is an important part of managing dairy farms. Understanding why cows are removed and how long they stay in the herd helps improve animal welfare and farm productivity. In this study, we looked at data from 26 dairy farms in Southern Brazil over a 10-year period. We found that nearly one in four cows was removed each year, mostly due to health problems like reproductive failure, udder infections, and leg or hoof conditions. Most cows were culled for reasons that farmers could not control. Larger and more productive farms had higher culling rates. Older cows, especially those with five or more calvings, were more likely to be removed. Spring had the lowest culling rates, while the beginning and the end of lactation were the riskiest periods. Interestingly, farms with more older cows produced slightly less milk, suggesting that simply keeping cows longer does not always lead to maximum profitability. These findings can help farmers make better decisions to improve both cow welfare and farm efficiency.

This study aimed to evaluate cow longevity and identify the main culling reasons in dairy herds in Southern Brazil. Two data sets from 26 predominantly confined Holstein herds were analyzed over a 10-year period (2007–2016). The first included 11,150 cows that were culled, died, or sold, and the second comprised 636,739 cows for demographic analysis. The average annual culling rate was 24.2%, mainly due to reproductive disorders (34.0%), mastitis/high somatic cell count (20.4%), and feet and leg problems (17.9%). Involuntary causes represented 89.5% of all culling. The death rate averaged 3.8%, with the most frequent causes being unknown (27.3%), other reasons (25.6%), tick fever (10.2%), and accidents/injuries (10.0%). Larger herds had higher culling rates than smaller ones (26.2% vs. 22.8%; p = 0.04), as did higher-producing herds compared to lower-producing ones (25.7% vs. 22.0%; p = 0.02). Cows with ≥5 calvings were culled more often (p < 0.01) than those in earlier lactations. Culling was lowest (p < 0.02) in spring and highest (p < 0.01) during early (0–60 d) and late (>420 d) lactation. Herds with a higher proportion of older cows had slightly lower milk yields (p < 0.01), indicating longevity does not always enhance productivity.