When it comes to milking a cow, the term 'complete' rarely enters the discussion. From an efficiency standpoint, speed is often much higher on the list of importance and complete is commonly seen as the opposite of speed.
From the cow’s point of view though, thorough milking is quite important and dairy producers recognize that it is vital to the sustainability of the cow.
When looking at what stimulates further milk synthesis, the alveolar portion of milk has a significant influence on production. In the situation of complete milk ejection, the presence of no milk stored in the alveolar portion of the udder can provide the stimulus for producing more milk.
If we could look inside the udder at milking time, we would see that on average, within a 12-hour interval, nearly 80 percent of the milk is held in the alveolar tissue and 20 percent in the gland cistern. This 20 percent is readily available for harvest, but the 80 percent needs oxytocin to assist in transfer from the alveolar tissue to the cistern to be made available for machine withdrawal.
The reason why thorough removal of milk from the udder is so important is that this empty alveolar tissue is the stimulus to the cow to produce more milk. If the tissue holds significant milk, as in the case of incomplete milk removal, the stimulus to produce more could be reduced. This interaction between milk synthesis and alveolar storage is why more frequent complete milk removal tends to lead to higher production levels on a per cow basis.
In summary, being smart, keeping it simple and maintaining sustainability are each important characteristics of milk harvest. The balance of these traits is key to providing consistent and quality milk harvesting. As with all things requiring balance, too much of one and not enough of another can lead to problems. When designing and evaluating any milk harvest system, a careful eye evaluating the balance between these traits will always provide a benefit.