Cows have not just one, but four stomach compartments, each of which performs a special function.
When cows graze on grass they swallow it half chewed and mix it with water in their first stomach called the Rumen. It is here that the digestion process starts.
Next, in the Reticulum the grass is formed into small wads called 'cuds'. Each cud is then returned to the mouth where the cow chews it 40 to 60 times for about one minute.
The chewed cud is swallowed into the third stomach, the Omasum, where it is pressed to reduce water and broken down further.
The grass then passes to the fourth stomach, called the Abomasum where it is digested. Finally it passes through the intestines where the cow takes out everything she needs to keep her healthy and strong and make milk.
A cow starts to produce milk when her first calf is born, which typically happens when the cow is about two years old. The farmer stops milking her two months prior to the birth so she can devote all her energy to producing her new calf.
It takes 50 to 70 hours for a cow to turn grass into milk. Depending on the breed, a cow can make between 25 and 40 litres of milk a day.
Cows need to be milked at least twice a day. Milk is collected from the cow's udder by a milking machine with suction cups in a milking shed on a dairy farm.
The farmer gently places the cups on each of the cow's four teats. From here the milk travels through a series of stainless steel pipes to a large refrigerated vat where it is stored and cooled.
At the factory the milk is pasteurised and then homogenised. Pasteurisation is the process of heating milk and milk products to destroy disease producing organisms. Homogenisation is where milk is filtered under high pressure through tiny nozzles to create a smooth texture.
The milk is then tested to make sure it is safe for human consumption and then put into cartons and plastic bottles.
Milk is also used to make cream, butter, yogurt, ice cream and cheese. All these products are known as dairy foods.
Yogurt has been consumed by humans for centuries. Ancient cultures originally used it as a way to preserve the goodness of milk. Today it is enjoyed as the perfect snack straight from the tub or used in dips, sauces, marinades and desserts.
Yogurt is fermented dairy food made by blending milk and live bacterial cultures, known as probiotics or 'friendly ' bacteria. These live cultures help break down some of the lactose in yogurt, making it easier to digest for people with lactose intolerance.
To make yogurt, skim milk powder is added to milk.\n\nThe milk is then homogenised and pasteurised.
Bacterial starter cultures are added which aids the setting of the yogurt.
The yogurt is stored in controlled temperatures (42ºC to 43ºC) for a period of between four and six hours, before being packaged and delivered to stores.
Sometimes, fruit or flavourings are added to enhance the taste and provide a wider range of products.
Cheese contains many of the nutrients found in milk, because it is made from milk. There are over 100 different types of cheese made in Australia and each has a special recipe. The most popular cheese in Australia is cheddar cheese.
To make cheddar, special bacteria called starter culture is added to milk.
The milk is then heated to 30 degrees celsius for 40 minutes and an enzyme called rennet is added to the milk which makes the milk set into what looks like milk jelly (curd).
The curd is cut into small pieces, heated and stirred for around 2.5 hours to remove as much of the whey as possible.
The curds and whey are pumped into a machine called a cheddaring unit, where the whey is drained away and the curds are stacked on top of each other. After a while they stick together creating one big block of cheese. This 'cheddaring' process takes about 45 minutes.
The curd is then cut up and mixed with salt and pressed into blocks, each weighing about 20 kg.
These blocks are put into sealed plastic bags and metal containers, before being placed in a cold maturing room and left to age or mature.
After it is matured, the cheese is ready to be distributed and sold.
At the factory, two things need to happen before the milk is packaged and sold.
The first process is pasteurisation. This is the name given to the process whereby milk is partially sterilised resulting in extended shelf life. Milk is heated to 72°C for no less than 15 seconds and cooled immediately, destroying any harmful bacteria and micro-organisms.
Next, the homogenisation process passes the milk under pressure through very fine nozzles, evenly dispersing the fat globules to create a smooth, creamy texture and taste.
The milk is now all set to be transformed into a wide range of dairy products, including cream, yogurt, cheese, ice cream, butter, or other types of milk such as skim, powdered, condensed, evaporated or flavoured milk.