Comparative Analysis of Free and Smart-Gated Cow Traffic Designs in Brazilian Automated Milking System Dairy Farms

Automatic milking systems (AMSs) are increasingly adopted in dairy farms, and barn design, particularly regarding cow traffic design (CowTD), plays a key role in system performance. This study evaluated the association between different CowTDs and operational and production indicators of AMS Brazilian dairy farms. The data were obtained from 149 commercial dairy farms equipped with AMS (average of 1.6 AMS per farm) encompassing approximately 14,642 lactating cows recorded between June and December 2025. Cow traffic designs were classified as free or smart-gated systems, including milk-first (MF) and feed-first (FF) configurations. Mixed models were used to evaluate the effects of regions, housing system, and CowTD on the number of lactating cows per AMS (NCowsAMS), milking frequency (MFreq), milk yield per milking (MYMilking), daily milk yield per cow (MYcow), daily milkings per AMS (MilkingsAMS), and daily milk yield per AMS (MYAMS). On average, farms milked 58 cows per AMS with a mean MFreq of 2.69 milkings/cow per day and produced 2227 kg of milk per AMS per day. Smart-gated CowTD supported a greater number of cows per AMS than free CowTD systems (FF = 57 and MF = 58 vs. Free = 53 cows/AMS). Although free CowTD increased MFreq to approximately three milkings/cow/day, this advantage did not translate into greater or equivalent MYAMS, despite MF and free CowTD exhibiting similar MYcow (37.0 and 37.2 kg/day, respectively). Even though free CowTD achieved the highest MilkingsAMS (Free = 156 vs. MF = 151 and FF = 143 milkings/day), it milked fewer cows per robot, resulting in lower MYAMS. Consequently, FF and MF systems produced 86 and 180 kg/day more MYAMS, respectively, than free CowTD. These results suggest that AMS performance is primarily driven by the NCowsAMS rather than MFreq alone. Under Brazilian commercial conditions, smart-gated CowTD systems appear to be more efficient, as evidenced by higher MYAMS, while allowing higher stocking densities, potentially without increasing labor requirements.