October 27, 2022 at 6:58 p.m.
Milking quickly, quietly, gently
“What we see from the industry is maybe the pendulum has swung a little bit too far in thinking about milking speed and putting cows through the parlor too rapidly,” Virkler said. “We want to make sure that we’re thinking about the things we know about the cow like how to get milk out of her and how to milk her well and not just pushing cows through the parlor.”
Virkler spoke during a seminar at World Dairy Expo Oct. 4 in Madison.
When a milking unit is attached to a cow, the cow goes through a high flow rate of milk. This is what Virkler calls the front end of the curve, which lasts for about two minutes. The back end of the milk flow curve is what happens after the peak flow rate. Ideally, once a unit is attached, the teats are full and ready to release milk.
“What we want to see is this rapid, uninterrupted increase of milk flow to the peak,” Virkler said. “We should see no decline in that peak until she is finished milking.”
The contrast to this ideal situation is called bimodal milk flow, or delayed milk ejection. This happens when the cow is not properly stimulated prior to the unit being attached. The milk flow will peak twice during the first two to three minutes of unit-on time. There is an initial rise in milk flow, then milk flow literally stops before a second rise in flow to another peak.
“What happens to the cow during that time is a lot of them will step and kick because they become uncomfortable,” Virkler said.
Virkler said a better prepping procedure can reduce the presence of a bimodal milk flow. The purpose of the prep procedure is to properly stimulate the cow. When the teat is stimulated, the nerve sends a signal to the cow’s brain. The signal tells the pituitary gland to release oxytocin into the bloodstream. The oxytocin travels to the heart, pumps to the aorta and hits the udder. When it reaches the udder, the oxytocin acts on the muscle cells and squeezes the milk out of the alveolar. Then time is needed from when it squeezes the milk until it hits the gland system, which is why there needs to be a waiting period for this to happen before attaching the unit.
“Remember that milk ejection is an inborn reflex,” Virkler said. “It is an involuntary act not under conscious control of the cow.”
Milk is present in two primary areas in the udder just prior to milking. The first place is in the gland cistern and the teat cistern. This makes up about 20% of the milk. That milk is accessible by simply opening the teat canal. The other 80% of milk is in the alveolar, which requires oxytocin and stimulation to be released.
When adequate levels of oxytocin are not released, there is an actual failure of milk let down. This results in a lower production of milk overall.
“We are leaving milk on the table by not properly stimulating these cows,” Virkler said. “Cows are leaving the parlor without being milked out because of bimodal.”
There are several ways to achieve a solid milking routine which will effectively stimulate the cow and harvest all the milk available. In any routine, time is of the essence. One example that Virkler uses starts with forestripping each quarter four to five times, or for 10 seconds, before pre-dipping the cow. The pre-dip should stay on the teats for 30 seconds before being wiped off. Finally, the unit is attached. The total time from forestripping to attaching the unit should be between 90 and 180 seconds. Virkler said this allows enough time for the oxytocin to kick in and milk to be let down.
When a good routine is not in place, there are negative influences on the cow shown by pain, mastitis and damaged teats. There are also negative influences in the parlor through lost efficiency and increased unit-on time.
“Without a good routine, it’s going to be a challenge to milk cows quickly, gently and completely,” Virkler said. “We’re going to have that bimodal flow. And when we have that, we don’t milk cows out well, and we don’t necessarily milk as quickly.”