Effects of automated short-term incomplete milking during peak to mid lactation on udder firmness, heart-rate variability, and behavior recordings in dairy cows

Incomplete Milking can strategically be used to induce short-term milk yield reduction, benefiting dairy cows’ metabolism without affecting long-term productivity. However, while intermitted milking has been associated with elevated udder pressure and discomfort in dairy cows, incomplete milking´s welfare effects remain less well studied. The aim of this study was to evaluate the effects of automated short-term incomplete milking on udder filling and udder firmness, as well as on the welfare of dairy cows, by assessing heart rate variability (HRV) and behavior recordings. Udder healthy, multiparous dairy cows in peak- to mid-lactation were randomly assigned to the complete milking treatment (COMP; n = 23, 95 ± 49 days in milk, lactation number 3.0 ± 1.3 (mean ± SD)) or the incomplete milking treatment (INCL; n = 23, 93 ± 46 days in milk, lactation number 2.6 ± 0.8 (mean ± SD)). The incomplete milking consisted of two phases: In the 1st phase, milk withdrawal was gradually reduced by 9 %/day over 5.5 days, resulting in app. 40 % reduction and was followed by 3 complete milkings. Subsequently, in the 2nd phase, the 40 % reduction was maintained consistently for further 5.5 days. Milk yield did not differ between treatments before incomplete milking (COMP: 39.1 ± 1.42 kg/day; INCL: 40.2 ± 1.66 kg/day (mean ± SEM) and a 43 % reduced milk withdrawal was effectively achieved at the end of the 1st phase and throughout the 2nd phase. In INCL cows, udder filling increased, and udder firmness before milking was elevated on average by 18 % during the 1st and by 22 % during the 2nd phase, compared to COMP cows. After milking, udder firmness was on average 33 % higher in INCL cows throughout both phases. Udder health was not affected by incomplete milking and it had no effect on HRV indices, which remained consistent between groups and over time (P > 0.05). No defense behavior was observed in the milking parlor, and behavior recordings in the barn showed no differences between treatments. This study demonstrates that, even though automated short-term incomplete milking resulted in increased udder filling and firmness – suggesting elevated residual milk and internal udder pressure –, incomplete milking does not indicate adverse effects on the welfare of dairy cows based on the indicators evaluated in this study. These findings support incomplete milking as a viable management strategy for dairy cows.