Machine milking follows a consistent routine: prepare the udder, attach the teat cups, let the machine do its work, then detach and apply a post-milking dip. The entire process takes roughly 5 to 8 minutes per cow once everything is set up, but the details of each step matter for both milk quality and udder health.
How the Machine Works
A milking machine has four core components. The vacuum pump creates suction that draws milk out of each teat. The pulsator is an air valve that rhythmically opens and closes the rubber liners around each teat, alternating between vacuum and normal air pressure. This mimics the squeeze-and-release action of hand milking and keeps blood circulating in the teat tissue. The liners are the only part of the machine that actually touch the cow. They sit inside rigid metal or plastic shells called teat cups. At the bottom, a claw collects milk from all four teat cups and routes it into a bucket or pipeline.
Standard vacuum pressure for dairy cows runs around 43 kPa (roughly 13 inches of mercury). Higher pressures can speed milking slightly but increase the risk of teat damage. Pulsation rate typically falls between 55 and 65 cycles per minute, with a ratio of about 65:35, meaning the liner is open about 65% of each cycle and resting the other 35%.
Step 1: Prepare the Udder
Udder preparation follows a four-step sequence: dip, strip, dry, and attach. The whole process should take 60 to 120 seconds from first touch to putting the machine on.
Start by dipping each teat in a pre-milking sanitizer. Cover three-quarters of the way up each teat, all the way around. Most commercial pre-dips need 15 to 20 seconds of contact time before you wipe them off. Don’t rush this. Skipping contact time defeats the purpose of killing bacteria on the teat surface.
While the dip sits, forestrip each teat by hand. Pull 3 to 5 squirts of milk from each one into a strip cup or onto a dark surface. This serves two purposes: it triggers the cow’s milk letdown reflex by stimulating oxytocin release, and it removes the milk sitting in the teat canal, which carries the highest concentration of bacteria and white blood cells. Spend at least 10 seconds total on forestripping. While you’re at it, look at the milk. Clumps, flakes, or watery appearance can signal an infection.
After stripping, dry each teat thoroughly with a clean, single-use towel. One towel per cow prevents spreading bacteria between animals. Teats need to be dry before the machine goes on, because moisture lets bacteria travel upward into the teat opening under vacuum.
Step 2: Attach the Teat Cups
Timing matters here. Oxytocin, the hormone that triggers milk letdown, takes 30 seconds to 2 minutes to kick in after you first touch the udder. If you attach the machine too early, it’s pulling on teats before milk is flowing freely, which stresses the tissue. If you wait too long, oxytocin levels start to drop and you leave milk behind. Aim to attach the unit about 60 to 90 seconds after you began preparation.
Hold the claw in one hand and use the other to guide each teat cup onto a teat. Work quickly but carefully. The goal is to minimize the amount of air that enters the system as you attach each cup. Excess air intake causes vacuum fluctuations that can push milk droplets (and any bacteria in them) between teats. Fold the vacuum hose to reduce airflow while positioning cups, then release once all four are seated.
Once attached, check that the unit hangs squarely beneath the udder. A machine pulling to one side puts uneven pressure on the teats and can cause the cups to slip or crawl upward.
Step 3: Monitor While the Machine Milks
Most of the actual milking is hands-off. Milk flow starts strong, peaks within the first minute or two, then gradually tapers. A typical cow finishes in about 5 to 8 minutes, though individual variation is normal. Watch for teat cups that have slipped, fallen off, or started making a hissing sound from air leaks. If a cup falls, don’t put it back on a clean teat without sanitizing it first.
Some machines have milk flow indicators or clear sections of tubing that let you see when flow slows. If you’re using a simpler setup without automatic sensors, watch the milk stream in the claw or tubing. When it thins to a trickle, the cow is nearly done.
Step 4: Detach at the Right Time
Removing the machine at the right moment protects teat health. Over-milking, leaving the unit on after milk flow has essentially stopped, exposes teats to sustained vacuum with little milk cushion. This can cause tissue swelling, small hemorrhages at the teat end, and greater susceptibility to infection over time.
Modern automatic detachers are set to pull the unit off when milk flow drops to a threshold, commonly around 600 grams per minute (roughly 0.6 liters). If you’re detaching manually, shut off the vacuum before you pull the cups away. Never yank them off while vacuum is still engaged, as this can injure the teat tissue. Most machines have a valve on the claw or a shut-off switch that releases vacuum. Once the air rushes in and you hear the suction break, the cups slide off easily.
Step 5: Post-Milking Teat Dip
Immediately after the machine comes off, dip each teat in a post-milking disinfectant. Submerge the lower 1 to 2 inches of each teat and let the dip air dry on its own. Don’t wipe it off. The teat canal stays partially open for 15 to 30 minutes after milking, and this is the window when bacteria are most likely to enter the udder. The post-dip creates a protective barrier while the canal closes.
In cold weather, keep cows inside until their teats are fully dry. Wet, freshly dipped teats exposed to freezing temperatures can crack and chap, creating openings for infection.
Keeping the Equipment Clean
After every milking session, the entire system needs to be flushed and sanitized. Rinse with warm water first to clear out residual milk before it dries. Follow with a hot alkaline wash to dissolve milk fats and proteins, then an acid rinse to remove mineral deposits. The rubber liners degrade over time and develop micro-cracks that harbor bacteria. Replace them on the schedule recommended by the manufacturer, typically every 1,200 to 2,500 milkings depending on the material.
Check vacuum levels regularly. The system should hold steady within a narrow range of its set point. Fluctuating vacuum usually means a leak somewhere: a cracked hose, a worn liner, or a failing gasket. Unstable vacuum is one of the most common mechanical causes of udder infections.
Spotting Udder Health Problems
The forestripping step is your first line of defense. Abnormal milk (clots, discoloration, watery consistency) is the most obvious sign of mastitis, an infection of the udder tissue. But many infections are subclinical, meaning the cow shows no visible symptoms and the milk looks normal.
Somatic cell count, a measure of white blood cells in milk, is the most reliable indicator of udder inflammation. Healthy milk typically stays below 200,000 cells per milliliter. Counts above that suggest the immune system is fighting something. Many dairy operations test bulk tank samples and individual cows regularly. Some in-line milking systems also measure the electrical conductivity of milk in real time. Infected quarters produce milk with higher conductivity (above roughly 5 mS/cm), though conductivity alone isn’t definitive since healthy and infected milk readings can overlap. A jump in conductivity for a specific cow compared to her own baseline is more informative than a single reading.
Teat condition is also worth watching. Redness, swelling, cracking at the teat end, or a hard ring of tissue forming around the teat opening can all indicate the machine settings need adjustment or that the unit is staying on too long.