Delayed milk ejection in modern dairy farms
A successful and efficient milk harvest depends on the milk ejection reflex. For proper milking, the milk ejection reflex must be started and followed by enough latency time (time from stimulation to milk unit attachment) before the milking process starts. Failure to do so often results in bimodal milk letdown or delayed milk ejection (DME). Many studies have reported the consequences of DME, including its impact on milk yield. However, some recent studies challenged the former consensus of no impact. Therefore, further research could help to elucidate the effects of this DME on farms that represent current management practices. The aim of this thesis was to explore some of the impacts and associations of DME in modern dairy farms.
The objective of our initial project was to find a practical method to identify DME in large milking data sets. We used data from 4 farms equipped with continuous milk flow meters and focused on the average flow rate of 4 intervals after unit attachment (0-15 s, 15-30 s, 30-60 s, and 60-120 s). For 528 cows, we compared these intervals to digital vacuum meters as the gold standard to detect DME. Our results showed that the flow rate during the 30-60 s interval can be used to identify DME events. This new use for this technology can be used to assess large data sets for management or research purposes.
Next, we investigated the association of DME and yield in the long term. Using the 30-60 s flow rate to identify DME, we evaluated milking data from 8447 cows from 4 commercial farms during 30 consecutive milkings. We found that in a period of 10 days, higher frequency of DME milkings resulted in milk yield reduction. This confirms that DME has a negative impact on yield. Therefore, dairy farms should make efforts to prevent it and avoid losses in yield.
In our last study, we explored the association between the premilking experience of the cows— walking speed, time walking to and waiting at the holding pen— and DME and yield. We obtained data from 167 cows from 4 farms during 13 consecutive milkings. We found that time in the holding pen is positively associated with yield, reinforcing the importance of providing good cow comfort in the holding pen. We also found that cows that walked faster or waited for longer times had higher risk of DME; however, the relationship between speed and DME was modified by the time in the holding pen. The higher risk of walking faster could be diminished by longer waiting times. Farms could use this information when planning cow movements to the milking parlor.
While DME is well known, its full impact remains unclear. Further research is needed to better understand its importance for modern dairy farms and for cows.
Paola Bacigalupo Sanguesa is originally from Chile. After obtaining her veterinary degree from Universidad de Chile, she obtained a Master’s degree with a focus on epidemiology from Colorado State University. She then joined Michigan State University Extension, where she decided to pursue a PhD from the College of Veterinary Medicine. Her research was focused on the practical aspects of milking physiology. She continues to work for Extension, helping dairy farms with issues related to animal welfare, milk quality and udder health, parlor and milking efficiency, and employee education.
