ANN 111: Principles of Animal Nutrition and Feed Technology (2+1)

ADDITIVES THAT FACILITATE DIGESTION AND ABSORPTION

 Grit

• Poultry do not have teeth to grind any hard grain, most grinding takes place in the thick musculated gizzard.
• The more thoroughly feed is ground, the more surface area is created for digestion and subsequent absorption. Hence, when hard, coarse or fibrous feeds are fed to poultry, grit is sometimes added to supply additional surface for grinding within gizzard.
• When mash or finely ground feeds are fed, the value of grit become less. Oyster shells, coquina shells and limestone are used as grit.

Buffers and Neutralisers

• During maximum production stage ruminants are given high doses of concentrate feeds for meeting demands for extra energy and protein requirement of the animal.
• The condition on the other hand lowers the pH of the rumen. Since many of the rumen microbes cannot tolerate low pH environment, the normally heterogeneous balanced population of microbes become skewed, favouring the acidophilic (acid-loving) bacteria.
• The condition often leads to acidosis and thereby upsets normal digestion.
• The addition of feed buffers and neutralisers, such as carbonates, bicarbonates, hydroxides, oxides, salts of VFA, phosphate salts, ammonium chloride and sodium sulphate have been shown to have beneficial effects.
• Recently the use of baking soda (NaHCO₃) has been shown to increase average daily gain by about 10 per cent, feed efficiency by 5 to 10 per cent, and milk production by about 0.5 liter per head per day.

Chelates

• The word “Chelates” is derived from the Greek word “Chele” meaning “claw” which is a good descriptive term for the manner in which polyvalent cations are held by the metal binding agents. Prior to union with the metal these organic substances are termed as “ligands”.
• Ligand + mineral = chelate element.
• Organic chelates of mineral elements, which are cyclic compounds, are the most important factors controlling absorption of a number of mineral elements.
• A particular element in chelated form may be released in ionic form at the intestinal wall or might be readily absorbed as the intact chelate.
• Chelates may be of naturally occurring substances such as chlorophyll, cytochromes, haemoglobin, vitamin B₁₂, some amino acids, etc., or may be of synthetic substances like ethylenediaminetetracetic acid (EDTA.)