Dynamics of culling risk of Holstein cows in US organic dairy herds

The study aimed to analyze the culling dynamics of cows in US organic dairy herds based DHI-reported reasons. In addition, the overall cow longevity in these herds was evaluated. A total of 287,927 lactation records from cows calving between 2018 and 2022 across 434 organic dairy herds from 31 US states were evaluated. Annualized rates of live culling and death were calculated, and the distribution of culling reasons was assessed by parity, days after calving, season, year, and geographic region. The average age at culling and its association with lifetime genetic merit were also examined. The average age at culling was 62.4 mo. Reproduction was the leading reason for culling (27.0%), followed by died (13.2%), mastitis (12.7%), and low production (12.1%). Overall, the annualized culling rate was 28.4%, with 24.7% due to live culling and 3.7% associated with died. Seasonal variation was observed in culling due to reproduction, with a decline during the winter and an increase after summer. Early lactation was a high-risk period for culling reasons died, disease, and other udder problem, and late lactation was associated with elevated risk of culling due to reproduction, low production, feet and legs, injury/other, and mastitis. Cow-level factors such as calving season, parity, and cow-relative 305-d mature equivalent (305ME) milk yield were significantly associated with risk of dying within 60 d after calving. The risk of died within 60 d after calving was greater for cows calving in the fall compared with those calving in winter, spring, or summer, and higher for primiparous cows than for cows in parity ≥4. Herd-level variables, including herd-relative 305-ME milk yield and herd size, were significantly associated with the risk of dying within 60 d postpartum. These same factors, along with the calving season, were associated with the risk of live culling during the first 60 d postpartum. High-producing cows based on high cow-relative 305ME milk yield were more likely to be culled for feet and legs, reproduction, and died, whereas low-producing cows had higher odds of being culled for low production, mastitis, and udder problems. A moderate negative correlation was detected between age at culling and genetic merit indices. These findings highlight that culling dynamics in US organic dairy herds are influenced by lactation stage, parity, milk production, herd-level characteristics, and calving season.