How do hen’s intestines work?
“Healthy guts make happy hens”
The intestines of a hen are designed to digest food, absorb nutrients, manufacture others nutrients that they cannot absorb from their food but are essential for systems such as the immune system.
Intestinal anatomy
Intestines are designed to maximise absorption of nutrients from the gut and onward transportation into the blood stream. This is facilitated by the hen having a very large surface area of intestine compared to their relative small size. The diagram below shows the "wiggly" shape of the intestinal villi, which line the surface of the small intestine. This undulating surface creates a much longer surface area over a short length of gut than a straight lining would. The intestines are continuously exposed to challenged from the outside environment, from ingested food and water. The risk of invasion or damage from this exposure is increased in hens through having such an extensive surface area of intestine.
The lining of the villi are only a single cell thick, made up of villus cells. This creates a very thin barrier between the food and microbes inside the lumen of the intestine and the blood stream lying within the intestinal walls. This structure is designed for the bird to absorb nutrients rapidly, and to facilitate a rapid and effective immune response as and when needed.
Immune defence
You may think it's only the skin of a bird which contacts the outside world, but actually the intestines are also continuously exposed to the outside world. Thes exposures includes food and treats that hens ingest, or microbes or compounds in the environment as hens forage and groom. The bird's immune system must work hard to prevent invasion of potential disease-causing microbes along the massive surface area created by the villi. Luckily, beneficial microbes within the microbiome are there to help the birds out. Read here for more information about the intestinal microbiome and how it helps our hens.
Intestinal function
Birds produce a range of enzymes which digest food inside the intestinal tract. They also rely on specialised bacteria to ferment certain food into essential vitamins and fatty acids that the bird cannot make itself. The collection of organisms living within the gut is called the “gut microbiome”. These bacteria are specially adapted to thrive in the environment of a hen's intestine. They are so specifically adapted that certain bacteria thrive in one part of the intestine, whereas others thrive in other parts. The caecae, the blind-ending sacs near the end of the intestine, are the main site of fermentation, and that’s why caecal poo's can be runnier, lighter coloured and sometimes contain bubbles, in comparison to the bulkier, firmer enteric faeces.
