The density depends on the content of water, fat and dry matter. If fat is removed from the milk the density will go up. If the milk contains extraneous water the density will go down. This fact can be used as an indicator for adulteration. Milk also contains protein which makes your body strong.
Some modern dairies pay according to the protein content of the milk .
27 Never add anything to your milk. The dairy will check the density of your milk. If it is not correct, you will get less or no money for your milk. Your milk should look, smell and taste good . 31 Dirt There should be no dirt.