Are you milking your cows efficiently while optimizing milk yield and milk quality? The goal in any milking routine is to synchronize timing between milk letdown and unit attachment. Units should be calmly attached to clean, dry teats.

Wallace jodi
Veterinarian / Ormstown Veterinary Hospital
Dr. Jodi Wallace, DVM, M.Sc., is a dairy producer at Anderson Farms/Silverstream Holsteins and pa...

Milk letdown is a reflex. In order to optimize milking efficiency, it is important to understand the physiology of milk letdown.

Milk is stored as two different fractions in the udder: the cisternal fraction (which is the milk immediately available in the teat end and gland cistern and represents less than 20 percent of the total milk stored) and the alveolar fraction (the udder tissue).

It is the movement of milk between these two spaces that allows for continuous milk flow. Stimulation of teats is needed to release oxytocin from the posterior pituitary gland.

Stimulation time includes the hands-on tactile stimulation of the teats for a minimum of 15 seconds. (This should include the time to pre-dip, forestrip, clean and dry teats.) Once a certain threshold of oxytocin is reached, the muscle cells in the udder tissue contract, and the milk is released into the cisternal part of the udder.


Timing is also very important for milking efficiency. If timing from initial teat prep to unit attachment (prep-lag time) does not coincide with oxytocin release and milk letdown, there will be a temporary cessation in milk flow, called bimodal letdown.

timing is everything when it comes to an effective milking routineBimodal letdown can be present as either a partial or a complete stop in milk flow. This is due to the cisternal milk being emptied before the letdown of alveolar milk.

More practically, it may be seen as the “empty or dry claw” shortly after initial attachment. The goal for prep-lag time is 60 to 90 seconds (with an upper range of less than two minutes and 30 seconds).

Pre-milking stimulation is essential as it allows for oxytocin release and consequently milk letdown. Forestripping some milk from each quarter before milking is one of the best ways to stimulate oxytocin release.

Forestripping also helps identify clinical cases of mastitis and removes milk that is higher in bacteria and somatic cells.

With a proper stimulation, “overmilking” (milking at full vacuum with low or no milk flow) at the beginning or at the end of milking may be avoided. Less overmilking means less trauma to teat ends.

Healthy teat ends are essential as they form the primary barrier to mastitis pathogens in the cows’ environment. Therefore, to achieve good milk letdowns and reduce overmilking, your milking procedure should include:

  1. Adequate stimulation time (minimum of 15 seconds).
  2. Proper prep-lag time (with a goal of 60 to 90 seconds).

Minimizing unit-on time and time spent in low flow or low vacuum at the beginning and the end of milking can impact cow behavior during normal milking. Automatic take-off settings can be set aggressively (shorter or no delay, high flow rates when detached) only when proper pre-milking stimulation and prep-lag times are achieved.

Milking cows calmly is essential for milk letdown and proper milkouts. If cows are stressed, painful or scared, adrenaline is released. This counteracts the effects of oxytocin, resulting in incomplete milkouts.

You can evaluate the effectiveness of milking procedures by comparing your data with the goal listed in Table 1.

Commonly used paramenters and goals for milking parlors

If you don’t have computerized data, simply stand back, get out your stopwatch, observe and time udder prep and milk letdowns in the claw after unit attachment. In order to properly evaluate letdowns, it is important to observe milk flow throughout the whole milking.

Do this for a random cross-section of your herd and look for a pattern. Finally, ask yourself these important questions:

  1. Do I have enough udder prep time (stimulation) in my pre-milking procedure?

  2. Is the prep-lag time adequate?

  3. Are the units removed in a timely manner?

  4. Are cows milked calmly?

In conclusion, periodic evaluation of your milking routine will benefit both you and your cows. A proper milking routine can reduce unit-on times, optimize milk harvesting and improve udder health in your herd.  end mark

PHOTO 1: Cows love routine – effective milking procedures are a win for everyone.

PHOTO 2: Timing is everything when it comes to an effective milking routine. Photos provided by Jodi Wallace.

Jodi Wallace