🥛 Milking: The Let-Down Reflex, Hygiene and Routine

Most people think milking is a mechanical job. The milk is in the udder, you squeeze, it comes out. That picture is wrong, and everything else in this module follows from correcting it.

Only a small part of the milk in a cow's udder is sitting loose in the teat and the large cistern above it, ready to be squeezed out. The great majority of it is held up in the fine ducts and in the alveoli - the tiny sacs of tissue where milk is actually made. That milk is not accessible to your hands or to a machine. No amount of squeezing will pull it down. It has to be pushed down, by the cow herself.

The push comes from a hormone called oxytocin. When the udder and teats are stimulated - washed, massaged, handled, or the first streams stripped out - the cow's brain releases oxytocin into her bloodstream. It reaches the udder within seconds and makes the smooth muscle wrapped around each alveolus squeeze. That squeeze forces milk out of the tissue and down into the cisterns and teats where you can get at it. This is the milk let-down reflex, also called the milk ejection reflex, and without it you are milking maybe a fraction of what the cow has.

So the first thing to understand is that your hands do not get the milk out of the cow. The cow gives it to you, and your job at the start of milking is to ask her properly.

How long does the asking take? The commonly cited target is roughly 60 seconds of udder and teat stimulation before you start the actual milking. The workable range is about 30 to 60 seconds. That range is not a sloppy figure - it moves with how full the udder is.

• For a less full udder, stimulation extending to around 90 seconds is appropriate. There is less milk in the cistern to begin with, so more of what you want is up in the tissue, and it takes more asking to bring it down.
• For a very full udder, a minimum of about 20 seconds can be enough. A great deal of milk has already accumulated in the cistern and the reflex has less work to do.
• For an ordinary cow at an ordinary milking, 30 to 60 seconds, with about 60 seconds as your working target, is the number to keep in your head.

Notice what this means in practice. The same routine is not right for the morning milking and the evening milking of the same cow, because the udder is not equally full at both. Morning, after the long overnight gap, she is fuller. Evening, after a shorter gap, she is emptier and needs more stimulation, not less.

There is a second and rather wonderful part of this. In a cow kept on a consistent routine, oxytocin release starts to be triggered not only by physical contact but by anticipation. The sound of the milker arriving, the rattle of the pail, the walk to the usual milking spot, the same time of day - these come to trigger let-down before your hand touches her. The cow has learned what is about to happen and her body prepares for it.

That single fact is worth more to a smallholder than any equipment on the market, and it costs nothing. It also explains, in one sentence, why a chaotic milking - different person, different place, different time, shouting, hitting, a strange dog in the shed - takes milk out of your pail. Fear releases a different hormone, adrenaline, which works against oxytocin and blocks let-down. A frightened cow physically cannot give her milk down properly. She is not being stubborn.

So the routine you build in the rest of this module is not fussiness and it is not somebody's idea of good manners. It is the practical management of a hormone. Calm, quiet, same person where possible, same place, same time, same order of actions every single day. That is what a cow's let-down reflex is built to respond to, and a cow that lets down completely gives you the milk that a cow milked in a rush leaves behind in her own tissue.

Lesson 1 said the cow gives you the milk when oxytocin reaches her udder. This lesson says the harder thing: she only gives it for a while. Oxytocin's effect on the udder is time-limited. It rises, it works, and it fades. If you are not milking while it is working, you are milking against a fading let-down, and the milk that was pushed down starts to be left behind.

So there is a window, and here are its edges.

Milking - hand-stripping, or attaching a machine cluster if you have one - should begin within about 60 to 90 seconds of first stimulation. That is the target. And no more than about 2 minutes should elapse between first stimulation and the start of milking. Two minutes is the outer limit, not the plan.

Read those two figures together with the stimulation times from Lesson 1 and the routine writes itself. You stimulate for roughly 60 seconds. You start milking at 60 to 90 seconds. There is no gap in the middle for wandering off to fetch a pail, chase a calf out of the shed, or answer somebody at the gate. Everything you need must be in your hand or beside you before you touch the udder for the first time.

There are two ways to get this wrong and both of them cost you.

Starting too soon means you begin milking before oxytocin has taken effect. The tissue has not squeezed yet, so the only milk available is what was already loose in the cistern. You get a little, then it stops, and you are working an udder that has nothing coming down into it.

Starting too late means the oxytocin pulse has already passed its peak. The milk was pushed down while you were doing something else, and now the push is fading. Whatever you did not take during the pulse stays in the tissue.

Both mistakes produce the same measurable symptom, and it has a name: dead time. Dead time is the gap between starting to milk and milk actually flowing well. It is easy to see once you know to look for it - you are working, and nothing much is coming.

Dead time is not just annoying. It has three real costs.

First, it lengthens the total milking time for every cow, every milking, twice a day, for the whole lactation. Add that up over a year and it is a serious amount of your own labour spent achieving nothing.

Second, in a machine system it increases teat-end strain, because the machine keeps running with poor milk flow. Vacuum acting on a teat that is not delivering milk is exactly the condition that damages teat ends, and a damaged teat end is a broken barrier against the bacteria you met in the mastitis module.

Third, and most seriously, poor timing is associated with reduced milk removal and poorer udder health outcomes over time. Milk left behind in the udder is not just lost income for that milking. Residual milk is a feeding ground, and incomplete emptying is bad for the gland.

There is one more finding that tells you where to look for this problem in your own shed. The effect of bad timing is described as most noticeable at the milking with the fullest udder - typically the morning milking, after the long overnight gap - and less pronounced at the emptier milking, typically the evening.

That may seem backwards at first. Surely a full udder is the forgiving one? But think about the volume at stake. The morning milking is the big one. A given percentage of milk left behind is more litres in the morning than in the evening, and the fullest udder has the most milk that depends on a proper let-down to move it. So if you are going to be precise about your timing at exactly one milking a day, make it the morning one.

Here is the honest practical difficulty. Sixty to ninety seconds is not a long time when you are also washing an udder, drying it, and stripping four quarters into a cup. It is achievable, but only if the sequence is practised until it is automatic and everything is prepared in advance. That is why the next lesson gives you the sequence in order, and why the last lesson of this module is about routine rather than technique. The skill here is not strength or cleverness. It is being ready before you start.

This lesson is the sequence itself. Seven steps, in order, every milking. What matters is not memorising a list but understanding what each step defends against, because a step you understand is a step you will not skip when you are tired.

Step 1. Wash your hands before handling the udder. Your hands are the main vehicle by which contagious mastitis organisms - Staphylococcus aureus, Streptococcus agalactiae, Corynebacterium bovis - move from an infected cow to a clean one. They also carry ordinary dirt and spoilage bacteria straight into the milk. Wash before you start and between cows.

Step 2. Wash and dry the udder and teats, ideally with an individual cloth or paper towel for each cow rather than one cloth dipped back into a shared bucket. The shared wet cloth is one of the most reliable ways ever invented to spread contagious mastitis through a herd - it goes into a communal bucket, onto an infected udder, back into the bucket, and onto the next cow's teats.

And note the second half of that step, because it is the half people skip. Drying matters as much as washing. A wet teat lets water, and the bacteria in it, run down the teat and into the milk, and into the teat canal itself as milking starts. A washed but undried udder can be worse than one left alone, because you have mobilised the dirt and given it a route down.

Step 3. Strip a few streams of foremilk from each quarter into a separate cup - not onto the floor, and not into the bulk pail. This step does two jobs at once, which is why it earns its place inside a very tight time window. It provides udder stimulation, starting the let-down timer from Lesson 1. And it lets you see clots, flakes, or watery and discoloured milk that flag clinical mastitis in that quarter, before that milk goes into the pail with everything else. The next lesson deals with the strip cup in full.

Step 4. Milk within the let-down window. Quarter by quarter if hand milking, working efficiently rather than stopping and re-starting stimulation partway through. Everything in Lesson 2 lives in this step.

Step 5. Dip or spray the teats with a post-milking disinfectant, where you can get one. Here is why this step is placed after milking rather than before. The mechanical action of milking, by hand or machine, leaves the teat canal open. For a period after milking it is a road into the gland, and environmental bacteria find it easiest to enter at exactly that moment. A post-milking dip covers and protects the teat while that road is still open.

Which product, and at what concentration, is not something this course can tell you. The teat dip products registered and available in your country, and their approved concentrations, are set by your national authority and by what is actually on the market where you live. Ask your agrovet or veterinary officer what is registered and how it is to be diluted, and follow the label. Do not improvise a disinfectant dip from something else in the store.

Step 6. Milk suspect or known-infected cows last, or with separate equipment and separately washed hands. This is the milking-order rule from the mastitis module, and it is free. If you know a cow has a problem quarter, she goes to the end of the queue, so nothing she sheds is carried forward to a clean cow in that session.

Step 7. Handle the milk hygienically from the moment it leaves the cow. A clean, food-grade container - not a general-purpose plastic bucket that also carries chemicals or feed. Straining. And immediate cooling. Hygiene at the cow is entirely wasted if the milk then stands for hours in a dirty uncovered can in the sun, and Lesson 5 covers this in detail.

Two things to notice about this sequence as a whole.

First, it is cheap. Water, a cloth per cow, a cup, a clean container. The only item with a real cost is the teat dip, and six of the seven steps work without it.

Second, it is ordered, and the order is not arbitrary. Hands before udder. Wash before dry. Strip before milk. Milk before dip. Clean cows before dirty ones. Cow before container. Each step protects what the next one is about to touch, and doing them out of order undoes the ones before.

This lesson takes two of the seven steps and does them properly, because they are the two that cost nothing and are skipped most often.

First, the strip cup.

A strip cup is any small container with a dark surface or a fine mesh screen that lets you see what comes out of the teat. A cup with a black plastic base works. A cup with a fine strainer over it works better, because clots catch on the mesh where they are unmistakable. If you have neither, a clean dark-coloured bowl or a mug will do the job today - what you need is contrast, so that a flake or a clot in white milk is visible.

The procedure is simple. Before milking, strip the first few streams from each quarter into the cup and look at what came out. Each quarter separately. Then look, properly, in the light - not a glance while thinking about something else.

What you are looking for is anything abnormal: clots, flakes, stringy material, milk that is watery and thin rather than white and opaque, or milk that is discoloured - pink or bloody, yellowish, or grey. Any of these are the visible signs of clinical mastitis in that quarter.

This is your free clinical check, done twice a day, on every quarter of every cow, in about thirty seconds. It is the only mastitis test in this entire course that requires no equipment, no reagent, no laboratory and no cost. And it is the earliest warning you will get of a clinical case, because it catches the first abnormal milk before you have had time to notice the cow is off.

Now the rule about where that foremilk goes, and there are three wrong answers and one right one.

It does not go into the bulk pail. If a quarter is producing clots, you have just put clots and a heavy bacterial load into the milk of every other cow in the pail. The whole point of looking is to keep that milk out.

It does not go on the floor of the milking area either, and this catches many people. Squirting foremilk onto the floor puts mastitis organisms - possibly contagious ones - onto the surface where the cows stand and where splashing can carry them back onto teats. You have created an environmental source.

It does not go onto your hand to look at, for the same reason as the floor plus the added problem that your hands then go onto the next cow.

It goes into a cup, and the cup gets emptied somewhere away from the milking area and washed before the next milking. That is the whole rule.

Now the milking order.

The principle is that infection travels forward through a milking session, from the cow you milk earlier to the cow you milk later, on hands, on cloths, and on equipment. You cannot make that impossible, but you can decide which direction it travels in.

So you milk from clean toward dirty. Healthy cows first. Cows you suspect next. Cows you know are infected last. If a cow has a quarter you have scored on the CMT, or one that has ever shown clots, she is at the end of your queue. Where a cow's problem is serious, use separate equipment for her, and wash your hands after her before touching anything else.

Heifers and freshly calved cows generally belong near the front, because they have had the least opportunity to pick up an infection and you want to keep it that way.

This costs nothing at all. It is a decision about sequence, made once, written down, and followed. And it is one of the very few mastitis control measures that works even when you have no reagent, no dip, no gloves and no money.

The habit that ties this lesson together is writing it down. Keep a simple sheet where you milk: cow, quarter, date, what you saw. "Cow 3, back right, 12 March, flakes in the foremilk." Two of those entries a fortnight apart on the same quarter tell you far more than either one alone, they tell your veterinary officer exactly where to look, and they tell you, at the end of the season, which cow has actually been costing you money and which one you merely remember as troublesome.

Everything so far has been about the cow. This lesson is about the equipment and the water, because milking hygiene fails just as often on the container side as on the udder side, and a farmer who does the seven steps perfectly and then pours into a dirty can has wasted the whole effort.

Start with water, because most hygiene failures are really water failures. You cannot wash what you have no water to wash with, and planning the supply is part of designing the milking operation, not an afterthought.

Here are sourced reference figures for the water needed per wash, by milking method:

• Hand milking: 10 litres hot and 20 litres cold per wash.
• Bucket milking (a bucket-type milking machine unit): 20 litres hot and 40 litres cold per wash.
• Pipeline milking: 30 litres hot and 60 litres cold per wash.

Notice what those figures tell a smallholder hand-milking one or two cows. Even at the smallest scale, you should plan on the order of 10 litres of hot water and 20 litres of cold, per wash, for the milking area and equipment. That is entirely on top of the cow's own drinking water, which must be clean, plentiful and always available.

This is a real design decision, not a detail. If your water source is a long walk away and you carry it by hand, you will not wash properly, no matter what you intend, because nobody carries thirty litres twice a day out of goodwill. Solve the water supply first - a tank, a closer tap, storage near the milking area - and the hygiene becomes possible. Try to solve the hygiene without solving the water, and you will fail slowly and blame yourself.

Hot water matters specifically because milk residue is fatty, and fat does not come off in cold water. Cold water rinses; hot water with a suitable detergent removes the film. A container that is only ever rinsed cold builds up an invisible layer of milk residue on the inside, and that layer is a bacterial reservoir that reinfects every batch of milk you put in afterward. A can that looks clean and smells slightly sour is a can with a residue problem.

Now containers. The rule is food-grade, not general-purpose.

A food-grade container is one made and intended for holding food. Stainless steel milk cans and food-grade plastic are the standard options. What is not acceptable is a general-purpose plastic bucket, a repurposed paint or chemical container, or a jerrycan that has previously held fuel, agrochemicals, detergent or feed. Two problems arise with these. The plastic itself may not be intended for food contact. And porous or scratched plastic holds residue of whatever was in it before, in scratches you cannot scrub out.

A smooth surface is the other half of the rule. Milk residue and bacteria live in scratches, dents, cracks and worn seams. An old can with a rough interior or a cracked lid cannot be cleaned properly no matter how hard you scrub it, and it should be retired from milk use and put to another job. Check the inside of your can by hand and by eye, in good light, once a week.

Then straining. Milk should be strained through a clean filter or cloth as it goes into the container, to take out hair, dirt, bedding and any visible foreign material. Two cautions. A straining cloth is itself a piece of milking equipment and must be washed and dried between uses, or it becomes a source rather than a filter. And straining removes what you can see - it does not remove bacteria, does not remove anything dissolved, and does not turn dirty milk into clean milk. It is the last physical tidy-up, not a rescue.

Finally, the gap. From the moment milk leaves the teat, its temperature is around body heat and bacteria in it start multiplying. Every minute it stands warm and uncovered is a minute they are working. So the milk goes into a clean covered container immediately, stays covered, stays out of the sun, and moves toward cooling or delivery as fast as your route allows.

What happens after that - how fast it must be cooled, how cold, and what to do when you have no electricity - is the whole subject of the module after next. What this lesson establishes is the handover: your job at the milking is to put clean milk into a clean covered container quickly, so that the cold chain starts from the best possible position rather than trying to rescue a bad one.

This lesson puts the module together, and its argument is simple. The value is not in any single step. It is in doing the same steps, in the same order, at the same time, every single milking, for as long as the cow is in milk.

Start with why sameness itself produces milk.

Lesson 1 said that in a cow on a consistent routine, oxytocin release begins to be triggered by anticipation - the sound of the milker, the walk to the milking spot, the time of day. That only happens if there is a routine consistent enough for her to learn. A cow milked at six one morning and half past eight the next, by three different people, in two different places, has nothing to anticipate. She gets no early let-down, so all of it has to be produced by physical stimulation, and you are already starting from behind.

So consistency is not tidiness. It is a production input, and it is free.

What needs to be consistent:

• The time. Milking intervals should be as even as you can manage.
• The place. The same spot, the same tie, the same standing position.
• The person, where you can manage it. Where you cannot, the routine must be identical between people, which is what the written card is for.
• The order of cows. Clean toward infected, as in Lesson 4, and otherwise the same sequence day after day.
• The order of actions. Hands, wash, dry, strip, milk, dip - never varied because you are in a hurry.
• The handling. Calm, quiet, no shouting, no hitting, no dogs in the shed. Fear releases adrenaline and adrenaline blocks let-down.

Now write it down. A single card, in your own words, numbered, pinned where you milk. This matters most on the day you are ill, or travelling, or at a funeral, and someone else milks. Without a card they will do it their way, and their way will not include a separate cloth for each cow or a strip cup or a milking order, because they do not know why those things exist. One session done wrong can put a contagious organism into a clean cow, and you will spend the next six months paying for it without ever knowing which day it happened.

The card should carry the timings from Lessons 1 and 2 in plain words: stimulate about 60 seconds; start milking between 60 and 90 seconds; never let two minutes pass. Those numbers are the part a helper is most likely to get wrong and least likely to guess right.

Now look back and see what these few minutes actually protect, because milking is the point where four separate systems in this course meet.

Udder health. Contagious mastitis is, in its transmission, a milking-hygiene problem. Hands, cloths, equipment, and milking order are the whole story of how Staph aureus and Strep agalactiae move around a herd. The seven steps in Lesson 3 are the control, and no drug can substitute for them.

Yield. Let-down timing decides how much of the milk in the udder actually comes out. A rushed, inconsistent or frightening routine costs milk directly, at every milking, from a cow you are feeding either way.

Milk quality and shelf life. This is the one people find hardest to believe. Milk quality does not start deteriorating in the can - it starts from the bacterial load introduced at milking. The keeping quality you will measure with the tests in the next module is largely decided before the milk ever reaches a container. Milk that starts with a low bacterial count keeps longer at any temperature.

And one honest limit. Milking hygiene does not remove brucellosis or bovine tuberculosis organisms from the milk of an infected cow. Those organisms come out of the udder in the milk itself, and no amount of washing, dipping or careful handling takes them out. That risk is controlled downstream, by heat treatment, and it has its own module. Do not let a very clean milking routine persuade you that raw milk from an untested cow is safe. Those are separate questions with separate answers.

What milking hygiene does do is prevent the enormous range of ordinary spoilage and mastitis organisms that make milk unsellable, unsafe and short-lived for entirely different reasons. That is a large enough prize on its own.

So: same time, same place, same order, same hands, calm cow, sixty seconds, start by ninety, cloth per cow, cup before pail, dip after, infected last, clean covered container, straight to cooling. Written on a card. Done twice a day. That is the whole job, and done properly it is worth more than most of the things a dairy farmer is tempted to spend money on.