Back to: Animal Husbandry SS 1
Digestion in Ruminants
Ruminant animals like cattle, sheep and goat feed mainly on grass and they can ruminate or chew the cud because of the complex nature of their stomach.
The digestion in ruminants can be explained properly with the aid of the diagram.
When a ruminant animal like a cow wants to feed, it cuts the grass and swallows it with minimal chewing. The grass passes from the mouth through the oesophagus to the rumen where the rumen, grass the is stored temporarily. In the grass is acted upon by micro organisms like bacteria and protozoa which digest the cellulose and synthesise some amino acids needed by the animal from non-protein nitrogenous substances.
When the cow has finished filling the rumen, it finds a cool place and lies down quietly. By anti-peristaltic movement of the stomach, the undigested grass passes from the rumen to the reticulum from where it re-enters the oesophagus (regurgitate) back to the mouth. The food is now chewed properly by using the molar and premolar teeth (chewing the cud) into a semi-liquid cud which is re-swallowed. This liquid cud now moves into the omasum from where it passes to the abomasum (the true stomach). The whole process is called rumination.
In the abomasum, enzymes are secreted
and act on the food. Further digestion and absorption of the food take place progressively along the digestive tract. The digested food is then absorbed into the blood through the villi in the small intestine while the undigested food passes to the large intestine where it is removed through the anus as dung or faeces.
Digestion in Non-ruminant (Pig)
Pig has only one stomach. It does not chew the cud neither does it utilise roughages properly. The digestion in pigs can be understood properly with the aid of the diagram.
The pig feeds mainly on basal feeds like maize, cassava and other mashed food. Digestion of food takes place in four areas of the tract:
(i) Mouth: In the mouth, the food is chewed and mixed with saliva which contains an enzyme called ptyalin. The ptyalin converts starch to maltose. The food is now swallowed and moves by peristaltic movement to the stomach.
ii) Stomach: In the stomach, two enzymes, enin and pepsin, are present. Renin acts on milk or it helps to curdle milk while pepsin converts proteins to peptones under the influence of an cid medium. The thick liquid called chyme now passes to the duodenum.
iii) Duodenum: Digestion also takes place here. Three enzymes are present and they act on different foodstuffs.
(a) Amylase: This enzymes converts starch to maltose
(b) Lipase: It’s converts fats and oil to fatty acids and glycerol
(c) Trypsinogen: It converts protein and peptones to polypeptides. These enzymes are secreted by the pancreas. The digestion of fats and oil is added by the bile which is secreted by liver and stored in the gall bladder.
(iv) Small Intestine: The wall of the small intestine secretes many enzymes which complete the process of digestion.
The enzymes are the following: (a) Lipase which converts fats and oil to fatty acids and glycerol. (b) Erepsin converts polypeptides to amino acids. (c) Maltase converts maltose to glucose. (d) Sucrase converts sucrose to glucose and fructose. (e) Lactase converts lactose to glucose and galactose.
The end products in digestion include the conversion of: (i) protein to amino acids (ii) starch to glucose (iii) fats and oil to fatty acids and glycerol.
These end products (amino acids, glucose and fatty acid and glycerol) are absorbed in the small intestine by a structure called the villi. The undigested food materials are passed to the large intestine from where they are ejected through the anus as faeces or dung.
The digestion of food in rabbit (a non ruminant) is just like the pig except that rabbit can feed properly on grasses which are digested in the large caecum which contains micro organisms like bacteria and protozoa.
Digestion in Domestic Fowls
The domestic fowl is a monogastric animal and has a simple stomach. The digestion in fowls can be explained properly with the help of the diagram.
The fowl has no teeth but the food is picked up by the beak. This food then passes on to the crop through the oesophagus. This food is stored temporarily in the crop where it is moistened and fermented by some bacteria. The food now passes on to the proventriculus where digestive enzymes are secreted on the food.
The proventriculus is often regarded as the glandular stomach because it secretes digestive enzymes on the food like pepsin and amylase.m From the proventriculus, the food moves to the gizzard where grinding takes place. With the aid of small stones or grits, the food is ground by the gizzard. From the gizzard, the food now moves to the duodenum and small intestine where further digestion and absorption take place while the undigested food materials are removed from the tract as faeces.
Importance of Digestive System
(i) It aids the ingestion of feed.
(ii) It promotes the digestion of feed.
(iii) It ensures the absorption of digested feed.
(iv) It helps in the ejection of undigested feed.
(v) It aids the secretion of productive hormones and digestive enzymes.
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