The Association of Delayed Milk Ejection with Milking Performance in Holstein Cows in a Large Dairy Herd with Suboptimal Premilking Teat Stimulation

Simple Summary Here, we investigated the associations of delayed milk ejection with the average milk flow rate, milking duration, and duration in a low milk flow rate in cows in a large dairy herd with suboptimal premilking stimulation. Our second aim was to study the association between peak lactation milk yield and delayed milk ejection. We found that delayed milk ejection was associated with a decreased average milk flow rate, increased milking duration, and increased duration in a low milk flow rate. Further, we found an association between peak lactation milk yield and delayed milk ejection such that cows with lower peak lactation milk yield had greater odds of delayed milk ejection. Our data suggest that delayed milk ejection has a negative impact on milking performance, and that peak lactation milk yield may serve as a proxy for the risk of delayed milk ejection. Future research is warranted to test if delayed milk ejection can be mitigated through, for example, a modified milking routine regimen, and if such a modified regimen has the potential to improve the milking performance in dairy cows.Abstract The primary objective was to investigate the association between delayed milk ejection (DME) and the average milk flow rate, milking unit-on time, and duration in a low milk flow rate in Holstein dairy cows in a large dairy herd with suboptimal premilking teat stimulation. Our second objective was to study the association between peak lactation milk yield and the occurrence of DME. This longitudinal field study was conducted at a 4300-cow dairy farm with a thrice-daily milking schedule over a 1-week period. We analyzed data from 61,677 cow milking observations from 2937 cows. Delayed milk ejection was defined as present if the 30-60 s milk flow rate was <= 3.1 kg/min. The mean average milk flow rate (MAMF, kg/min), mean milking unit-on time (MMUT, s), and mean duration of a low milk flow rate (MLMF, s) were calculated as the mean values from the 21 milking observations. General linear multivariable models revealed associations of DME with MAMF, MMUT, and MLMF. A multivariable ordinal logistic regression model revealed an association between peak lactation milk yield and DME. Cows with lower peak lactation milk yield had greater odds of exhibiting a higher frequency level of DME. The observed associations between DME and milking performance indices suggest that DME can negatively affect milking and parlor efficiency. Peak lactation milk yield may serve as a proxy to estimate cows' risk of recurrent DME. Future research is warranted to test if alleviating DME through, for example, a modified milking routine influences the milking performance indices described herein.