Witaifi, A. A., Ali, A. B. A., Siegford, J. M. 2018. Stall and feed bunk stocking rates impact cows' diurnal behavior and activity in automatic milking system farms. Journal of Veterinary Behavior 24, 48-55.

High stall stocking rates have been shown to alter behavior of cows in parlor-milked systems; however, no studies have examined stocking rates for cows milked with automatic milking systems (AMSs). Therefore, we examined the influence of stall and feed bunk overstocking on cows' behavior, displacements, cows' activity, and rumination time in an AMS dairy farm. Each of 2 pens contained 60 cows/pen, 58 free stalls, and 60 headlocks. The effect of stocking rate was examined using 3 treatments applied separately to stalls and feed bunks (100% = 58 stalls or 60 headlocks available for 60 cows; 120% = 50 stalls or 50 headlocks available for 60 cows; and 150% = 40 stalls or 40 headlocks available for 60 cows). Each stall or feed bunk treatment was applied separately for 1 week in a randomized order that was different for each pen, with a 1-week washout period between treatments. Data were collected during the last 2 days of each treatment week. Activity level, time spent ruminating, and the number of displacements were recorded for both feed bunk and lying stall treatments. The number of cows lying, perching, or standing in lying stalls was recorded in response to stall stocking rate treatments, and the number of cows eating or standing at the feed bunk was recorded for feed bunk stocking rate treatments. Statistical analyses were performed using R software (version 3.3.1). Overstocking stalls to 150% reduced the number of cows lying and standing in stalls but increased the number of cows perching in stalls compared with 100% or 120% stocking rates (all P ≤ 0.05). Moreover, overstocking feed bunks to 150% increased the number of cows eating and standing at the feed bunk after delivery of fresh feed compared to 100% or 120% stocking rates (all P ≤ 0.05). Finally, overstocking of either lying stalls or the feed bunk to 150% reduced time spent ruminating and increased cow activity and number of cows displaced from stalls or the feed bunk in comparison with lower stocking rates (all P ≤ 0.05). Thus, changes to cows' behavior when overstocked above 120% in AMS farms may detrimentally affect welfare and health. Producers can use these results to determine optimal stocking rates in AMS dairies, allowing them to optimize facility design and management to maintain good welfare and production without wasting space or resources.