Today we're going to be talking about milking cows, from hand milking to robotics. Today, we're going to be learning about the structure of the bovine mammary gland. We're going to be learning about the milk produced and stored within the udder of the mammary gland of the cow. We're going to talk about preparing the teat and the udder for milk removal and the various milking systems that exist on daily farms. The mammary gland is really four separate glands. Each quarter has one teat and one teat opening. They are the front and rear quarters which you can easily see demarcated on the picture. The front quarters are left and right front quarters and left and right rear quarters. The rear quarters are larger than the front quarters, as they extend up behind the inner thigh area of the cow. 60% of the milk volume comes from the rear quarters because 60% of the weight of the mammary gland is in the rear quarters. There's extensive blood supply to the mammary gland to bring nutrients and to make milk. You can see on the left front quarter the veins that are draining the mammary gland. And then in front of the quarters and the udder, there is a large mammary vein, which is roughly two inches in diameter. Which drains the udder and brings the blood supply back to the udder for more nutrients to make milk. If you notice, there's two distinct halves also, from the rear of the cow. A very large suspensory ligament goes down the middle of the udder and with that, there's a large attachments of ligaments to hold the udder in place. The udder itself, weighs 50 pounds and the milk can be from 50 to 70 pounds. And so this supporting structure must support 100 to 120 pounds of milk. The secretory tissue in the mammary glad, otherwise known as alveoli, is organized within lobes or lobules of the mammary gland. The epithelial cells synthesize milk within these alveoli, which is pictured on the right. The suckling release from the calf nursing the cow releases oxytocin. Oxytocin travels through the bloodstream which is around all of the alveoli. And the muscle cells that surround the epithelial cells will contract, pushing the milk from the lumen into the duct system. And then the duct system is made up of the gland cistern and the teat cistern as well, when the milk travels down the ducts to be excreted. When you hand milk a cow, you must trap the milk in teat cistern. And so, you are basically preventing the milk from going back up into the gland. And then if you just do downward motion by expressing one finger at a time down over the teat, it will express the milk. Hand milking is done by milking two quarters simultaneously in an alternating motion and this fills the bucket very rapidly. You have to be careful, however, that the cow does not move and kick your bucket of milk over because there's nothing protecting it. It takes 15 to 20 minutes to milk a cow by hand. This is usually reserved for backyard cows. The milking machine, which became developed in the late 1800s, is now designed as four teat cups with a soft inflation, or a soft rubber inner lining, that goes within the hard stainless steel shell. The shells all come together into the bottom which is known as the claw. Milk machines use a vacuum produced by a pump for the milking action of a cow. Because the vacuum cannot be on the teat all the time, there's a pulsator that was designed which alternates between vacuum and air within the space between the inner lining and the shell. When the vacuum is on, the liner opens and milk flows. This is the milking phase. When air is injected into the system, the liner collapses and massages the teat. This is the rest phase. The rest phase is very important so that the teat can have its blood supply put back up in so that we're not damaging the teat. And this is the rest phase. The pulsator works about once a second or 60 times a minute but swinging between vacuum and air to milk the cow. With machine milking, you have to stimulate the udder just the same as the calf would nurse by hand stripping the cow. Then the cow is dipped with a disinfectant on all the teats so that she is clean and all the bacteria have a chance to be killed. Once the teat is dipped, it remains on the teat for about 30 seconds. Then it is dried with a cloth towel, then the towel is turned over, without the dips on it. And the teats are again wiped as part of the simulation process for milk let down. From start to finish, it's taken about one minute between stripping and attaching the unit. And that is the best for milk let down. Once the unit is attached, you can see how the milk flows quickly into the claw. And that is a good let down. Milk immediately jets in there and you can see the pulsatile nature of it coming into the claw because of the pulsator going between vacuum and rest. It takes about five minutes to milk a cow with a machine. Dairy cows are milked two to three times a day. And the milking machine is very gentle and comfortable for the cow, as you can see, because they do not jump around. They're very comfortable in this setting. Cows in stalls need their milking machine to come to the cow. There's usually four or five units that are attached, so four or five cows can be milked at one time. When a cow is finished, the unit is then moved to the next cow and inserted into the milk line at a different spot. The milk line runs the entire length of the barn and milk is transferred to the milk holding tank. Milk is lifted from the base of the teat up over the top of the cow, which takes a bit more vacuum. Cows in a milking parlor, cows come to the milking center. Several cows are milked together. People stand lower than the cows and milk flows downward which takes less vacuum. The same milk line, which is a low line, is then transferred the milk to the holding tank. Robotic milking is becoming more popular. Robotic milking milks about 60 cows for one robot and so we can have less labor on the farm. And the cow comes to the robot so she can decide when she would like to be milked. The cow is behind a metal gate and so she does not see the robot moving. But the robot must prepare the teat the same way as a regular milking machine. The robot disinfects the teat and there's a brush action that cleans the teat, very soft and gentle. The robot uses laser light to find the teat and to attach the unit. It also uses laser light to clean the teat. And the robot will memorize the cows from a transponder and so it will eventually know exactly where the teat placement should be for that cow. In summary, milking requires preparation of the teat for a good milk let down and oxytocin release. The majority of cows are milked with a milking machine two to three times a day. And the robotic milking can reduce farm labor and allows cows to choose when they would like to be milked.
