Interactions of Year, Calving Season, and Parity on Productive and Reproductive Performance in High and Moderate Yield Friesian Herds

This study compared the productive and reproductive performance of Friesian cows across two distinct commercial operations: The first farm (Farm 1) is classified as a large-scale, high-yield dairy operation (8,564 cows, ≈9,500 kg total milk yield TMY). The second farm (Farm 2) is classified as a medium-scale, moderate-yield dairy operation (2,531 cows, ≈5,500 kg TMY). The objective was to assess the interactive effects of parity, season of calving, and year on both farms. Results showed that summer calving optimizing TMY for 1st parity on both farms, while winter calving optimized TMY for 3rd parity on Farm 2. Moreover, Farm 2 maintained short, stable dry periods (DP ≈60−70 d), while Farm 1 showed historical DP failures in older cows. Both farms demonstrated successful, targeted improvements in 3rd parity efficiency by year (Farm 2 days open: 63.95 d), but shared a persistent challenge: poor reproductive performance in 1st parity heifers, especially those calving in spring. The findings underscore that optimal management requires a parity-specific, season-adjusted strategy tailored to the farm's scale, prioritizing biological stability over milk yield in moderate operations.