Working in the parlor is like driving the chopper because one gets to see the results of one’s labor. The parlor, like the chopper, needs to be running properly to maximize the harvest. Here are some simple ideas to make your parlor run well.
Remember that milk runs downhill. In low-line systems, milk can run downhill all the way from the teat to the receiver jar unless there are obstructions to the flow. When running downhill, the flow in the hoses and lines is laminar, meaning there are layers of air and milk. This keeps the teat end vacuum stable and close to the line vacuum.
In contrast, for milk to move uphill, a slug forms which temporarily blocks the airflow. A vacuum drops behind the slug for the length of time it takes for the slug to move up the hose to the line. This results in slower milk flow from the udder and longer milking times as well as greater vacuum fluctuation at the teat end.
In high-line systems, the line vacuum needs to be higher to maintain adequate vacuum levels at the teat end. This means the vacuum applied to the teat ends at the beginning and end of milking will be higher, and this can cause teat-end damage.
Most parlors are designed to take advantage of laminar flow by allowing milk to flow downhill to the line, but sometimes barriers are inadvertently put in place. For example, in many parlors the milk hoses are way too long, creating a valley for the milk to flow into and requiring a slug to move the milk out. In other parlors, hose length is not standard, so milk runs downhill for some cows but not for others. It is not always possible for milk to run downhill from every udder on every cow, but it should be possible for the vast majority. Otherwise, one is wasting one of the big advantages of a low-line system.
Unit positioning is important. Units should be square on the udder when viewed from the rear or the side. Poor positioning can result in poor milk out of one or more quarters. Poor positioning can also lead to admission of air and squawking, which can result in longer milking duration, poor milk out and mastitis. Poor positioning also can be painful to the cow. Some, but not all parlors, will need hose positioners to maintain proper positioning. All the milking technicians need to use the supports, and they should understand the reasons for their use. Poor positioning sometimes happens because hoses are too long. Poor positioning can also lead to slug flow if hoses are tipped to one side or the other.
Venting is needed to move milk away from the teats. The vents can be in the mouthpiece, the short milk tube or the claw. Vents need to be examined at the beginning of milking to make sure they are open; otherwise, it will be difficult to move milk away from the teats. Another problem we commonly see is systems with vents in more than one place, like the claw and the short milk tube, for example. This may result in lower claw vacuum at peak milk flow and longer milking duration. While the effects may be subtle, the effect is greater on high-producing, fast-milking cows.
Teat end health is important. Less than 20% of cows should have teats with scores of 3 or 4, and less than 20% of teats should score 3 or 4. A teat with a score of 3 or 4 will have fronds of tissue protruding more than 1 mm from the teat end. Rough teat ends can lead to mastitis and longer milking times. Rough teat ends usually are caused by longer time milking in low flow.
Cleanliness really is next to godliness in a parlor. Teat barrels, and especially teat ends, need to be clean and dry. Bacteria do not have legs; they move in fluid, so wet teat ends facilitate transfer into the udder. A common mistake in many parlors is not drying the teat ends properly. Technicians often dry the barrels with a twisting motion but neglect to dry the teat end. They need to pinch the teat end with a clean towel or the clean side of a towel to get them dry. Cleanliness does not just apply to the teats. It is not uncommon to see the outside of liners and claws with caked manure. Bacteria can be transferred from the manure to the technician’s gloves, and then to the teat and ultimately can infect the cows. Keeping the rest of the parlor clean will encourage technicians to be clean.
You do not need to get every drop of milk out of the cow. A reasonable goal is for most cows to have between 100 mL and 250 mL left in the udder, or up to about 1 cup of milk. It is unusual to find parlors where most cows have 100-250 mL of milk left; almost always, cows are milked drier than this. Fewer than 20% of quarters should have more than 100 mL of milk left. Usually, when a quarter is not fully milked out, it is due to that quarter being slow milking or poor unit positioning. Trying to harvest every drop of milk leads to longer milking duration, longer times in low milk flow and possibly poor teat end health.
Milking preparation is important. Cows need at least 10 seconds of tactile stimulation, and units need to be attached when milk letdown occurs. Attaching too early or too late results in delayed milk ejection. Every minute of delayed milk ejection costs about 7 pounds of lost milk per day. Consistency is key in the routine. Often, we see consistency decline when an extra person comes into the parlor for a period of time, and there is not a clear definition of how the routine needs to change to maintain proper timing.
Cows should be comfortable during milking. A reasonable standard is less than 10% of animals kicking or stomping near the end of milking. If there are too many, it may be due to improper take-off settings, vacuum or pulsator settings or electrical problems.
Minimizing duration of milking is important because milking, by itself, is somewhat of a traumatic event. The most traumatic part of milking is the time spent in low milk flow, because the teat end vacuum tends to correlate inversely with milk flow. As milk flow drops, teat end vacuum will move toward whatever the line vacuum is. Changes that reduce milk flow tend to affect your best cows the most, because peak flow vacuum on those cows tends to be lower already. Keeping the parlor running smoothly helps you harvest the right amount of milk quickly, carefully and with comfort for the cow.       
Parts of this article were taken from Northern Valley Livestock Services December 2021 newsletter.
Bennett is one of four dairy veterinarians at Northern Valley Dairy Production Medicine Center in Plainview, Minnesota. He also consults on dairy farms in other states. He and his wife, Pam, have four children. Jim can be reached at bennettnvac@gmail.com with comments or questions.