Why does a cow have four stomachs?

Some people say a cow has four stomachs, but actually it has one stomach with four compartments. These four compartments are the rumen, the reticulum, the omasum and the abomasum.

https://www.reference.com/pets-animals/many-stomachs-cow-2b761b5b714dcb4c

Cows have four stomach 'compartments' called the Rumen, Reticulum, Omasum and Abomasum.

A cow has four stomach compartments.

https://en.wikipedia.org/wiki/Cow

A cow has 4 stomachs (or 4 stomach chambers) each with an important part to play in digesting food.

1.The Rumen this is very large and can hold up to 150-200 litres of partly digested food. The Rumen is full of bacteria and this softens the food. The bacteria ferments the carbohydrates in the food to allow the cow to produce energy. In doing so gas is produced (approx 500-1500 litres a day), approx 30% of this is methane gas and is expelled during belching. This is also how the foodstuff is passed from one chamber to the next.

2. The Reticululum This softens the food even further and forms it into small lumps of cud. The cud is returned to the cows mouth and chewed approx 40-60 times before being swallowed again. The reticulum also prevents large items from passing through the stomach this includes items which the cow has eaten which are not food, e.g plastic, packaging etc.

3. The Omasum This processes the cud further breaking it up and filtering it.

4. The Abomasum This works similar to the human stomach. The food is finally digested by the stomach juices and the useful nutrients are absorbed by the blood. The waste is then pushed out into the intestines and finally out into a big smelly cow pat! Its a long journey for a bit of grass.

https://animals.mom.com/what-are-the-functions-of-a-rumen-12582195.html