Assessing the effect of transitioning from tie-stalls to free-stalls with automatic milking system on dairy cattle welfare, milk production, and the environmental sustainability

• Animal welfare improved in free-stalls with Automatic Milking System compared to tie-stalls for dairy cows • The introduction of the Automatic Milking System increased milk production and feed consumption • Transitioning to free-stalls with Automatic Milking System mitigated the environmental impact of milk production This study evaluated the effects of transitioning from tie-stalls to free-stalls with an Automatic Milking System (AMS) on the welfare, productivity, feed consumption, and environmental impact of lactating Holstein Friesian cows over the course of one year in a small-scale farm. Cow welfare improved significantly after the transition, particularly for clinical indicators (e.g., 100% reduction in hindquarter, neck/shoulder and back injuries), lying synchronization (+2.6±9.27%), and affiliative behaviours, such as social licking, which were observed exclusively in this system (0.09 events/cow). Daily milk production increased after the transition (+16%); other production measures, including milk quality and reproductive performance, showed an improving trend, although not statistically significant, with the exception of milk fat content, which showed no improvement. Feeding behaviour differed before and after transition, with variations in the sorting index and concentrate proportions of the diet, though feed intake remained adequate. Energy consumption for milking ranged from 2.69 kWh per 100 kg of milk before the transition to an estimated 1.5–3 kWh after the transition, suggesting that AMS did not provide a significant energy-saving advantage. Importantly, the introduction of AMS played a key role in mitigating environmental impact, with a climate change mitigation of 27%. This reduction was primarily associated with increased milk production, which diluted the system's overall environmental impact.