Absorption and excretion in birds
Absorption in birds
Absorption of glucose occurs via both passive and carrier mediated transport system.
Passive transport appears to predominate in the duodenum and jejunum. Chicken has a sodium dependent carrier system for the active transport of sugars.
Carrier medicated transport of D -glucose is facilitated by a Na+-glucose co-transpoter protein.
Amino acids are also transported by Na+ dependent and energy dependent carrier mediated process in birds. Neutral amino acids are transported more rapidly than basic or acidic amino acids.
- Four system of amino acids transport have been identified in chicks:
- Neutral amino acids system
- Basic amino acids system
- Acid amino acids system
- A system for proline, beta alanine and related amino acids
Feces in birds
This material consisting of waste and undigested food mixed with the urine in the cloaca and eliminated from the body as faeces.
Typically it is a rounded, brown to grey mass topped with a cap of white uric acid from the kidneys.
Absorption of salt and water
Sodium, K+ and Cl– ions are almost completely absorbed. Na+ ions are involved in the transport of water, monosaccharides, amino acids, pyramidine and bile salts.
- Na+ is transported as-
- Na-co transport
- Cl– coupled transport and
- Diffusion by electro -chemical gradient.
Chloride ions are transferred through Cl– coupled Na+ transport
Association with Na+ co-transport of glucose
Diffusion by electro-chemical gradient.
K+ is absorbed by passive diffusion due to concentration gradient.
HCO3 absorption is by active transport.
Water is transported passively.
Intestinal absorption of Ca++ is by active transport. Vitamin D induces mucosal Ca++ binding protein and increases Ca++ absorption.
Mg++ is absorbed by active transport but its absorption is poor. Absorption of phosphorus is active process and related to active transport of Ca++.
Absorption of Fe++ is related to its level in mucosal cell. Absorption is limited by binding capacity of apoprotein (carrier protein).
Cu is absorbed in small amounts, Co and Mn are readily absorbed.
Fat-soluble vitamins A, D, E and K pass through mucosa passively as also water-soluble vitamins. Vitamin B12 requires an intrinsic factor secreted by stomach for its absorption by active transport.