Feed additives enhance animal nutrition by improving feed efficiency, preventing diseases, and increasing palatability. They are categorized into nutrient and non-nutrient types, each with their advantages and disadvantages. While they can boost animal performance, concerns include antibiotic residues and potential health issues.

1. Feed additives
Dr. G. Sri Manjula Reddy M.V.Sc
Department of animal nutrition

2. Feed additives
 Feed additive is an ingredient or combination of ingredients
added to the basic feed mix for the purpose of improving rate
of gain, feed efficiency, preventing and controlling diseases.
 Feed additives are broadly classified in to two types
1.Nutrient feed additives
2. Non nutrient feed additives

3. Advantages of feed additives
1.Increses feed quality, palatability and self life.
2.Improve animal performance.
3.Improve the final product.
4.Economise the cost of animal protein.
Disadvantages
1.Antibiotic residues in animal products
2. Development of Antibiotic resistant microorganism’s
3.Masks the bad quality food.
4. Causes allergy

4. 1. Additives that promotes growth and production
a. Antibiotics:
These are substances which are produced by living organisms (mold,
bacteria or green plants) and which in small concentration have the capacity
of inhibiting the growth of other microorganisms and even of destroying
them.
Quantity as an additive is much less than that used for therapeutic purpose.
Two types
Ionophore antibiotics :- Monensin, lasalocid, salinomycin, lysocellin
Non-ionophore antibiotics :-Tetracyclins, virginiamycin, Zn bacitracin,
tylosine etc..

5. Mode of Action of Antibiotics
1.Intestinal wall of animals fed antibiotics is thinner than that of untreated
animals, which improves the nutrient absorption.
2. Reduce or eliminate the activity of pathogens causing “subclinical
infection.”
3. Reduce the growth of micro-organisms that compete with the host for
supplies of nutrients.
4. Antibiotics alter intestinal bacteria so that less urease is produced and
thus less ammonia is formed. Ammonia is highly toxic and suppresses
growth in non-ruminants.
5. Stimulate the growth of micro-organisms that synthesize known or
unidentified nutrients

6. 2. Additives that facilitate digestion and absorption
a. Grit:
Poultry do not have teeth to grind any hard grain, most grinding takes
place in the thick musculated gizzard.
Oyster shells and limestone are used as grit
b. Buffers and Neutralisers:
Maximum production-high doses of concentrates-lowers the pH-
Acidosis
The addition of feed buffers and neutralizers, such as carbonates,
bicarbonates, hydroxides, oxides, salts of VFA, have been shown to
have beneficial effects.

7. C. Probiotics:
 Probiotic is defined as a live microbial feed supplement which beneficially
affect, the host animals by improving its intestinal microbial balance.
 Generally composed of organisms of lactobacilli and/or streptococci species,
Bifidobacterium, few may contain yeast cultures (Saccharomyces cervisiae)
Characteristics of good probiotic
 The culture should exert a positive effect on host
 It should be gram positive
Acid & bile resistance
Minimum no per gram (30X109CFU/g)
 High survival rate, multiply faster & should be strain specific.
 Neither pathogenic nor toxic to the host
 The adhesive capability of microorganisms must be firm & faster.
 Durable & stable so that product can be delivered alive to the intestines.

9. Prebiotic
Compounds other than dietary nutrients that modify the balance of
the micro floral population by promoting growth of beneficial
bacteria & provide a healthier intestinal environment.
Mannanoligosacharide (MOS)- Derived from yeast cell walls
Interfears with the attachment of harmful bacteria to gut wall.
Fructo oligosacharide (FOS)- Cereals
Fermented by favourable bacteria and gives competitive advantage
Symbiotic
Combination of probiotics and prebiotics

11. Enzymes
 Feed enzymes acts as biocatalysts to assist the digestion process and support
utilization of nutrients that otherwise go unutilized.
 Fibroenzyme is the first feed grade enzyme that is rumen stable.
The enzymes should fulfil the following criteria for practical application:
1. The enzymes must be active at the pH of the animals digestive system and
capable of surviving transit through the stomach.
2. They must be in a physical form in which they can be safely and easily mixed
into all forms of animal feed.
3. The products should be or a high standardized activity that will remain stable
both before and after incorporation into the feed or pre-mix.
4. The enzymes must be capable of surviving normal pelleting condition.

12. Diet Problem component Enzyme
Barley & Oats Beta glucan Beta glucanase
Wheat, rye, triticale Arabinoxylan Xylanase/
pentosanase
Fibrous material Cellulose Cellulase
Grains and seeds Phytate phosphorus Phytase

13. Chelates:
 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, hemoglobin, vitamin B12 some amino acids, etc., or may be of
synthetic substances like ethylenediaminetetracetic acid (EDTA.)

14. 3. Additives that affect the health status of livestock
 a. Antibloat compounds: Surfactants such as poloxalene is used to
prevent pasture bloat
 b. Antifungal additives: Mold inhibitors are added to feed liable to be
contaminated with various types of fungi such as Aspergillus flavus,
Penicillium cyclopium etc. Before adding commercial inhibitors all
feedstuff should be dried below 12 cent moisture. Propionic, acetic acid
and sodium propionate are added in high moisture grain to inhibit mold
growth. Antifungals such as Nystatin, sodium benzoate and copper
sulphate preparations are also used in concentrate feeds to prevent molds.

15. c. Anticoccidials
Various brands of anticoccidials are now available in the country to prevent
the growth of coccidia which are protozoa and live inside the cells of the
intestinal lining of livestock.
Ex:- Amprolium, Monensin, Lasalocid, DOT (3,5 dinitro toluamide)

16. 4. Additives that enhance feed intake
(a) Antioxidants:
Antioxidants are compounds that prevent oxidative rancidity of polyunsaturated fats.
Rancidity once develops, may cause destruction of vitamins A, D and E and several of the B
complex vitamins. Breakdown products of rancidity may react with lysine and thus affects
the protein value of the ration.
Ex:- Vit E, Vit C, Selinium, Ethoxyquin, BHT (butylated hydroxytoluene), BHA (butylated
hydroxy anisole) can serve as antioxidant in feed.
(b) Flavoring Agent:
Flavoring agents are feed additives that are supposed to increase palatability and feed
intake. There is need for flavoring agents that will help to keep up feed intake
1. when highly unpalatable medicants are being mixed
2. During attacks of diseases
3. When animals are under stress
4. When a less palatable feedstuffs is being fed either as such or being incorporated in
the ration.
Ex:- Monosodium glutamate (MSG) 0.2% - poultry
Ruminants prefer sweet compounds. Additionally cattle and goats respond positively to
salts of volatile fatty acids. Horses will often refuse musty feed when there is so little
mold that the owner fails to detect it.

17. 5.Additives that alter metabolism
(a) Hormones:
 Extensive use is being made of synthetic and purified estrogens,
androgens, progestogens, growth hormones and thyroxine or thyroprotein
(iodinated casein) to stimulate the growth and fattening of meat
producing animals.
 There is concern, however, about possible harmful effects of any residues
of these materials in the meat or milk for the consumers.
 These substances may induce cancer in human beings if taken over a
prolonged period through products of the treated animals.
(b) Implants:
Implants are hormone or hormone like products that are designed to release
slowly, but constantly, the active chemicals for absorption into the
bloodstream. These are implanted subcutaneously in the ear.(eg.)
diethylstilbesterol (DES).

18. 6. Additives that improves feed quality
Anticaking agents:
Anticaking agents are anhydrous substance that can pick up moisture
without themselves becoming wet. They are added to dry mixes to
prevent the particles clumping together and so keep the product free
flowing.
They are either anhydrous salts or substance that hold water by surface
adhesion yet themselves remain free flowing:
Calcium phosphate
Potassium and sodium ferrocyanide
Magnesium oxide
Sodium aluminium silicate
Sodium calcium aluminium silicate
Calcium aluminium silicate

19. Humectants:
These are substance which are required to keep the product moist, as
for example, bread and cakes. Anticaking agents immobilise moisture
that was picked up. Humectants are not or much use in poultry feed.
Sequestrants:
Certain metals – copper, iron can act as pro-oxidant catalytic and there
fore need to the immobilized. Sequestrants are compounds added to do
this.
These compounds should have affinity to metal ions and should prevent
the metal in becoming engaged in oxidative action. Most effective
sequestrants EDTA (Ethylene diamine tetra acetic acid). Calcium salt of
EDTA works satisfactorily as a sequestrants without interfering with trace
mineral metabolism.

20. Sweeteners:
 It is common constituent of food but yet used as additives. Eg.
Sugar
 Some are poorly digestible, may cause digestive upsets.
 Saccharin – extensively used during World War I. It is a compound
without any calorific value.
Pellet binders
 Calcium lignosulfonate, sodium lignosulfonate widely used pellet
binders in animal feeds.
 In rabbits lignosulfonate cause ulceration of colon and consequent
death, Hence sodium bentonite is used in pellets of rabbits.
Mycotoxin binding agents
Mycotoxin binding agents include activated charcoal, synthetic
zeolites, mineral clays such as Hydrated sodium calcium aluminum
silicate (HSCAS), sodium bentonite.