A bad turn of the rotary parlor

Observing a rotary parlor in operation.

Rotary parlors have been installed on more farms in Michigan as a way to efficiently milk a large number of cows. Managing the protocol of milking on a rotary is unique to each dairy. There is a lot of interest in reducing the number of workers needed by replacing them with automation or laborsaving methods or protocols.

Recently, Ashley Brzozowski, an intern with Michigan State University Extension, and I observed a rotary parlor in operation. One of the differences with observing milking in a rotary parlor versus another type of parlor is that one can stand at a spot and cows passing that spot will all be at the same stage of milking.

This rotary rotated counterclockwise with cows entering at around 11 o’clock on the dial if you were looking down at the platform. Milking units were attached at approximately 9 o’clock on the dial, and we stood at approximately 7 o’clock on that dial and watched cows as they approached that position.

What we noticed by looking at the milk flow in the claw of the unit was a high percentage, around 40%, of cows were experiencing bi-modal or bi-phasic milking. Bi-modal milking is when milk flow begins when the unit is attached, but stops soon (approximately 30 seconds) after starting because there was insufficient stimulation of the cow to cause milk letdown.

Milkflow stopped, but vacuum continued.  This puts stress on the teat ends particularly and, according to new research, may result in incomplete milk letdown by the cow even when she does let down her milk. Milk flow does restart because of the stimulation provided by the unit, but often not for 30-60 seconds after it stopped once the teat cistern was emptied.

Michigan State University research uses a cut-off of 10 percent of cows having bi-model milking as an indicator of a problem with the prep procedures for milking. This was clearly above that level. So what was causing it? Why was the problem so frequent?

The problem was not unique to rotary parlors. It is just that the rotary provided a simple way to detect the problem. The problem was the lack of physical stimulation of the teats 60-90 seconds prior to attachment of the units.

Physical stimulation of the teats causes the cow’s brain to send a signal to the pituitary gland to release oxytocin. This hormone travels through the bloodstream to the udder causing the individual milk cells in the udder to release their milk. If there is a failure to either provide effective stimulation or to wait the 60-90 seconds after stimulation before the milking unit is attached, then bi-modal milking will likely occur.

Effective physical stimulation can be provided by dry wiping the teats, massaging in teat dip, forestripping and drying the teats. When some of those steps are eliminated, or replaced by a mechanical cleaner that is not properly set or used, effective stimulation may not occur.

In the case of this parlor, other than the physical impact of “dry milking” the teats and of lost milk production from cows that let down less milk, there was an another consequence. Approximately 10 percent of the milking units dropped off within the first 20 feet of their attachment as milk flow stopped.

Unit drop-offs required one worker to leave his station where he and another worker unattached and reattached the units. Had this worker been assigned to a task that involved physical stimulation of the teats prior to unit attachment, it is likely that very little time would have to have been devoted to reattaching units.

MSU Extension, with the help of three Extension interns, is evaluating milking on farms throughout the state this summer to identify problems with bi-modal milking and overmilking. If you want to know more about this, please contact your MSU Extension Dairy Educator.

Problems identified during milking can be corrected, if they are known. In this case, the problems were not apparently caused by employee compliance with protocols, but with the protocol itself. How often is that the case on farms? Is it the case on your farm? MSU Extension can help.

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