Understanding Poultry Digestion

Instead of asking “Why did the chicken cross the road?” poultry hobbyists may better ask, “How does the chicken chew its feed without any teeth?” Even without teeth, chickens have one of the most efficient digestive systems in the animal kingdom. Let’s take a look at how the poultry digestive system works.

Food is taken in with the beak, which is the perfect tool for pecking feed in crumble or pellet form, small grains, grass or insects. Chickens are omnivores – meaning that, in addition to a commercial feed, they can eat meat (grubs, worms, the occasional mouse) and vegetation (grass, weeds and other plants). A small bit of saliva and digestive enzymes are added as the food moves from the mouth into the esophagus.

From the esophagus food moves to the crop, an expandable storage compartment located at the base of the chicken’s neck, where it can remain for up to 12 hours. The food trickles from the crop into the bird’s stomach (proventriculus or gizzard) where digestive enzymes are added to the mix and physical grinding of the food occurs.

The gizzard is why chickens do not need teeth. It is a muscular part of the stomach and uses grit (small, hard particles of pebbles or sand) to grind grains and fiber into smaller, more digestible, particles.

From the gizzard, food passes into the small intestine, where nutrients are absorbed. The residue then passes through the ceca, a blind sack along the lower intestinal tract, where bacteria help break down undigested food. From the ceca, food moves to the large intestine, which absorbs water and dries out indigestible foods.

This remaining residue passes through the cloaca where the chicken’s urine (the white in chicken droppings) mixes with the waste. Both exit the chicken at the vent, the external opening of the cloaca.

And don’t think of chicken manure as “waste” to be disposed of…it makes a great fertilizer for your flower beds or vegetable garden. Because it is high in nitrogen, it is recommended to let it age for a bit in a compost pile before adding it to your gardens.

6 Replies to “Understanding Poultry Digestion”

    1. Hi Bill,
      You asked a very common question, and there are schools of thought on both types of feed. Crumbles are usually easier for young birds that are just transitioning off of starter feed to eat because they are smaller particles. Also because of the particle size crumbles are a good choice for bantams and smaller breeds. Consumption is usually higher on crumbles than on pellets. Pellets, on the other hand, usually cause less waste and may be easier to feed in a self regulating situation because the feed tends to flow better in the feeder. Hope this helps with your decision!

  1. How do you determain the sex ? It seems as though I end up with more roosters than hens all being raised in my ” hatchery” and they get quite big before I can tell what is what.

    1. Hello Lin – It is difficult to tell the gender your chicks are before they either crow or lay an egg! Most hatcheries will sell you “straight run” chicks, which are NOT sexed. If you want females, purchase pullets, or “sexed” chicks. However, even the best hatchery only guarantees the accuracy to 90-95%. My first group of hens I bought were pullets, but I ended up with one rooster out of 10! The best way to go, so you know for 100% sure, are sex-linked breeds where the males are different colors than the females and therefore are easy to tell apart. It is a tricky process to tell the gender from their tiny physiology; since it is most accurate on day-old chicks. You must observe if the chick has a very small “bump” inside its vent or not. The chicks with the “bump” are males, and those whithout are females. Some females, however, have small bumps inside their vent which complicates the process further. It is something best left up to the experts unless you have been properly trained. Breeds differ, but within the first week or so, usually the females will begin to develop their wing feathers before the males and the male chicks will tend to be larger. This is one way to tell early-on, but nowhere near 100% accurate. Thanks for writing in and continue to enjoy raising your chickens; roosters and hens!

  2. The info above on “straight run” chicks in incorrect. Straight run chicks are NOT sexed. They come exactly as they hatch out of the eggs, both genders together. So I’m assuming that’s about 50/50 males/females.

    If you want pullets (aka hens) those come sexed and are usually marked pullets at the feed store. They are normally a little more expensive than straight run, because you are getting the premium chickens (the girls!).

    Yes, you will often have a rooster slip through once in a while. But the great majority of them will be girls.

    Best of luck to all chicken raisers!

    1. Thanks for catching that, Kim. I must not have had enough coffee that morning! Take care – Allison

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