• Question: why do cows have four stomachs and other animals that eat grass don't?

    Asked by ronald111 to Amelia, Izzy, , Sarah on 19 Mar 2014.
    • Photo: Isabel Webb

      Isabel Webb answered on 19 Mar 2014:


      Grass contains a chemical called cellulose, which is what makes plant cell walls rigid and strong.
      Animal digestive systems struggle to digest cellulose – it is very tough.

      The first chamber of the cow stomach holds lots and lots of undigested food, and has lots of bacteria in it – just like our stomachs. These bacteria help to break down food and start the digestion.
      The next chamber turns the undigested food into lumps – called ‘cud’. The cud is then returned to the cow’s mouth and the cow chews it even more – it’s teeth help break down the strong cellulose. This is why cows often seem to be chewing. They then swallow it, and it passes to the third chamber.
      In the next chamber the last of the cud is broken down, and it can pass into the last chamber.
      In the last chamber, the good parts of the food are absorbed into the cow’s bloodstream. Any waste leftover from the food goes through the cow intestine and comes out as a stinky cow pat!

      Other animals, like horses, have a stomach that does the role of the first two cow stomachs in one. The food then passes to a ‘hindgut’. In this hindgut are lots of bacteria that break down some of the food. The rest of the grass comes out in their poo. These animals then eat their own poo (YUCK!) and can digest a bit more of the grass from the poo. It is almost the same process as the cows chewing the cud. But sounds a bit more disgusting to us!

    • Photo: Amelia Frizell-Armitage

      Amelia Frizell-Armitage answered on 20 Mar 2014:


      The active chemical in coffee is caffeine. For us when we drink caffeine it has a stimulant effect. This means it can make us feel more awake and able to do things faster than we normally would. However the extent that caffeine effects people like this varies between individuals. Some people only need to drink one cup of coffee to feel super awake, whilst other people have to drink 2 or 3 to get the same effect. Coffee can even make some people feel quite ill.

      Plants are basically the same as us. If you water a plant with coffee, or sprinkle a few coffee grounds on the soil every day, you will find that this can help some plants grow faster! However, in some plants caffeine has no effect and grow rate doesn’t change when coffee is added, and like humans, some plants get quite ill when you water them with coffee. The caffeine can stop them growing properly so they grow much slower and end up shorter than normal plants.

      As well as direct effect on the plant, if you put your coffee grounds in the soil they will actually break down and add nutrients to the soil. In addition the coffee will attract worms which feed on it. The more worms are in the soil the healthier it is, as worms break down nutrients, and add oxygen to the soil. Both of these things are really good for plant growth.

    • Photo:

      answered on 20 Mar 2014:


      All the plants which we eat are made up of sugars joined up very very tightly in the form of cellulose.

      When we eat vegetables, (plants too) we are not very good at breaking this cellulose down, so this helps flush the rest of our foods along our digestive system which is a good thing because it gets rid of what we don’t need. We get our sugar much more readily from other foods, so we only need one stomach

      Cows on the other need to break this down, since they only eat grass. As i said earlier this cellulose is difficult to break down and get the sugars, so the cow has to take its time and break this down in stages.

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