You do know that chickens don’t have teeth, right?
Does the old saying “as rare as hen’s teeth” sound familiar?
If so, has it ever crossed your mind how chickens can ‘chew’ and therefore get the most out of their food if they don’t have teeth? After all, chickens are the most efficient converters of feed into meat of all land-based livestock species, so they must be doing something right.
So what’s their secret? How can they break down their food without possessing teeth?
The answer to this lies in a part of the chicken’s digestive tract called the “gizzard”. The gizzard is a specialised muscular organ and its role is to break the feed up into smaller, more digestible, particles. Just like teeth, it achieves this mechanically, using its thick, muscular walls to grind the feed pellets and grains together so that they break into smaller particles.
The digestive process of chickens actually starts well before the food enters the gizzard, however. As the food moves from the chicken’s mouth into its oesophagus, some digestive enzymes are added to it. From here it moves to the crop, which is an expandable ‘pouch’ where the food is stored. While water is added to the feed in the crop, which serves to soften the food particles before they move further down the digestive tract, the main role of the crop is simply to store food and regulate the rate at which it is released into the stomach, which is where digestion proper starts to happen.
Throughout the course of the day, the crop releases the stored food into the first part of the chicken’s stomach, called the proventriculus, where digestive acids and enzymes are added to the mix, combining to start the breakdown of food into smaller pieces. The food then passes into the gizzard to be broken into smaller, more digestible pieces, which allows the nutrients in it to be exposed to the digestive processes. From the gizzard, food passes into the small intestine, where the nutrients in it are actually absorbed.
Are chickens unique in having a gizzard?
Well no – all birds have gizzards. Crocodiles and alligators also have gizzards, as do earthworms, and some fish and crustaceans do too. Some non-bird dinosaur species are believed to have had gizzards too!
Are chicken gizzards important in any other way?
Chicken gizzards are a popular food in many parts of the world and are available for sale in Australia.
..and the answer to our original question?
So, chickens can chew! But unlike the fictionalised chicken shown in this animation, they don’t have ‘teeth’ – they have a gizzard to do the job instead.
Chickens are amazing animals – even without teeth, they have one of the most efficient digestive systems in the entire animal kingdom.