Some of the things we are taught as youth stick, unfortunately for my high school modern literature teacher, some things don’t. One of the things that stick with me is the thought that the average shot never hits the duck. Two feet in front and two feet behind on average hits the duck, but anyone who has ever fired a shot at anything will tell you, the hunted lives for another day in that instance.
On average, a dairy cow carries 20% of its milk in the cisternal portion of the udder at a point 12 hours from the last milking event. Why does that matter? It matters because the cisternal portion of the milk in the udder is more or less available to be harvested with little or no stimulation. Unfortunately in this instance a large number of cows today aren’t milked on a 12 hour interval. When we shorten the interval from 12 to 8 hours a lower percentage is available, when we lower production, as when the cow nears the end of lactation, the amount in pounds available is a moving target.
We are forced to set milking equipment to milk the average cow, knowing that the amount of milk the cow can give us before the stimulation is needed to supply additional milk then is critical. High 2 minute milk flows can be achieved and we have set systems up to harvest milk faster than ever. If we take the instance of a late lactation cow milking 60lbs a day being milked 3 times a day we are going to harvest, on average, 20lbs of milk in a milking event. If she carries these 20lbs as 20% cisternal we will then have 4lbs of milk to harvest before the alveolar portion is needed to support continued milk flow. The alveolar portion of the milk needs stimulation to assist in removal. If we assume an 8lb/min flow rate we then have 30secs of milking before we need this portion to kick in.
One of the most common things I see holding back good milking is a direct result of this math. The cow needs to be ready to participate to get us through this period at the front end of milking. Take a look in the parlor; do you see milk coming into the bowl and then slowing or stopping 30-60 seconds into milking? If so adjustment to lag time, time from touch to attach, or total stimulation time needs to be lengthened.
A dealer expressed to me a couple weeks ago that proper milking is like a golf swing, lots of moving parts, I couldn’t agree more.