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1. Importance of Zinc
Supplementation
Layer Bird Nutrition

2. Zinc Pharmacological Role
› Zinc plays multiple roles in poultry nutrition.
› It is a component of various enzyme systems such as:
1. Glutamic dehydrogenase
2. Alcohol dehydrogenase
3. Alkaline phosphatase
4. RNA polymerase
› They enzymes are responsible for metabolism of carbohydrate, protein and lipids.

3. Cont. …
› Zinc is essential and directly involved in catalysis and co-catalysis by the enzymes
which control many cell process including:
1. DNA synthesis
2. Normal growth
3. Brain development
4. Behavioral response
5. Reproduction
6. Foetal development
7. Membrane stability
8. Bone formation
9. Wound healing

4. Cont. …
› As a component of carbonic anhydrase, zinc helps in transport of CO2 from tissues
to lungs.
› Also it is required for utilization of vitamin A and conversion of pyruvic acid to lactic
acid.
› Zinc is a component of hormone thymosin (produced by thymus cell) which is
required for immunity purpose.

5. Zinc Deficiency
› Symptoms of zinc deficiency in young chicks includes:
1. Retarded growth
2. Shortening and thickening of leg bones
3. Poor feathering
4. Poor feed efficiency
5. Loss of appetite
6. Mortality in severe cases
7. Reduce bone ash

6. Cont. …
› Zinc deficiency has been shown to decrease:
1. Cellular immunity
2. Thymus and spleen development
› Zinc is important for proper disease resistance and its deficiency has resulted in:
1. Bacteremia
2. Parasitic infections
3. Alteration in high-density lipoprotein cholesterol

7. Cont. …
Zinc impacts immunity in poultry
– Zinc supplementation in breeder diets has been shown to enhance immunity of their progeny.

8. Cont. …
› In layer and breeding poultry birds, zinc functions in formation of eggs.
› Zinc deficiency affects the quality of epithelium due to role of zinc in protein
synthesis.
› It also indirectly affects epithelial secretion, by affecting the structure of epithelium or
directly during the synthesis of egg shell membrane.
› Zinc plays a role in the magnum during the deposition of albumen and in the isthmus
where egg shell membranes are produced.
› Dietary zinc source may have influenced hen day egg production and secretion of
reproductive hormones during sexual maturation.

9. › Majority of zinc and other trace elements in the egg are deposited in the yolk, and
much smaller quantities are deposited into albumen.
› Approximately 86% of the zinc originally present in the fertilized egg is transferred to
the chicks.
› On increasing zinc concentration in egg, hatchability increased.
› The increased hatchability was primarily due to decrease incidence of late embryonic
mortality when zinc level was increased in the egg.
› Supplemental zinc is essential in poultry diets to achieve normal reproductive
performance.

10. Zn Availability

11. Zn Availability
› Zinc is widely available in food sources but its bioavailability from different foods is
highly variable.
› Zinc is commonly supplemented in the diets of poultry and livestock because many
natural feed ingredients are marginally Zn- deficient.

12. Cont. …
Corn soya based diet
› It increases the demand of zinc in the diet.
› Cereal based diets including plant sources such as soya bean or cotton seed meal
cannot deliver enough amount of zinc to the animals due to chelating effect of
phytate.

13. Cont. …
Animal products
› They are the richest food sources of zinc, particularly the organs and flesh of beef,
pork and shellfish.
› They do not contain phytase, they are good sources of available zinc.
› They tend to be expensive.

14. Zinc & Phytic Acid
› Zinc has been supplemented in animal diets using inorganic salts such as oxides
and sulphates.
› Trace minerals tend to dissociate in the low pH environment of upper gastrointestinal
tract, leaving the minerals susceptible to various nutrients and ingredient
antagonisms that impair absorption.
› Phytic acid is able to form complexes with trace minerals that are very stable and
highly insoluble, rendering the minerals unavailable for absorption.

15. Chelated Zinc
› The word chelation is derived from the Greek word ‘chele’, meaning claw.
– It refers to a bonding formed between a metal ion (mineral) and a ligand (protein
or amino acid chelating agent).
› A chelated complex is an organometallic compound consisting of a mineral +
organic component (protein or polysaccharide)

16. Cont. …
› It is produced by reaction of a mineral salt with an enzymatically prepared mixture
of amino acids and small peptides, under controlled conditions.
– The ligand binds the metal at more than one point such that the metal atom
becomes part of a ring.
– The resulting ring structure protects the mineral from entering into unwanted
chemical reactions.
– Certain amino acids and protein digestion products such as small peptides are
ideal ligands because they have at least two functional groups (amino and
hydroxyl) that can form a ring structure with the mineral.

17. Cont. …
› Organic mineral sources exist in the form of:
1. Metal amino acid chelates
2. Metal proteinate
3. Metal specific amino acid complexes
› The primary chelated minerals used in animal feed are the trace elements:
1. Iron
2. Manganese
3. Cobalt
4. Copper
5. Zinc

18. Zinc Bioavailability
Bioavailability is defined as:
› The proportion of the ingested element that is absorbed, transported to the site of
action, and converted to a physiologically active form.
› Solubility is a critical factor for trace mineral absorption.

19. Cont. …
Trace Mineral Stability
› To increase uptake, chelated minerals should be stable in digestive tract of animals.
› Chelates are stable, electrically neutral complexes, which protect trace minerals from
chemical reactions during digestion that would render the mineral unavailable to the
animal.

20. Cont. …
Chelated minerals absorption
› Chelate minerals can be more effectively absorbed into the intestines than inorganic
oxide and sulphate.
› Zn-methionine provides a source of zinc with greater biological availability than zinc
from inorganic sources.
› Gill (1997) reported that chelated minerals are more biologically available in animal
digestive system than inorganic minerals and that perhaps resulted in less mineral
excretion and pollution of the environment.

21. Cont. …
› Clear indications of biological activity of zinc are:
1. The content of this element in liver
2. Accumulation of zinc in the bones
3. Levels of zinc in blood serum
› These are the indicators to ascertain the availability of this element in live animals.

22. Zinc Requirement
› Zinc requirement (mg/kg dry matter) are reported to be:
1. 40 for 0-8 weeks chicks
2. 35 for 8-18 weeks of age
3. 50 for laying hens and
4. 65 for parent stock

23. Cont. …
› The NRC (1994) set the requirement of zinc at 40 ppm.
› But the research data on which NRC was formulated were more than 10 years old
and do not represent the needs of modern strain of commercial poultry (Leeson,
2005).

24. Cont. …
› The most commonly used zinc for supplementation in animal diet is inorganic zinc
inform of zinc sulphate due to:
1. Low cost
2. Commercial availability
› It is a common practice in the broiler industry to formulate diets to contain 100- 120
mg supplemental zinc/ kg of diet.

25. Cont. …
› Burrell et al. (2004) reported improved performance when broiler consumed diets
containing 110 mg zinc/ kg of diet while NRC (1994) recommendation is 40 mg zinc/
kg of diet.
› Broiler and laying hens can tolerate 1-2 g/kg DM of zinc in their diet.
› Further increase in zinc concentration (up to 4 g/kg DM) leads to:
1. Loss of appetite
2. Retarded growth

26. Zinc Safety Margin
› NRC (1994) recommended 40 mg zinc/ kg of diet in broiler ration, but often diets are
formulated to contain zinc level of 120 mg/ kg of diet.
› From a practical standpoint, wide safety margins are often used to avoid trace
mineral deficiencies and allow birds to achieve their genetic potential.
› This higher level of addition possibly to reduce the deficiency under commercial
condition.

27. Zinc Excretion and Environment
› Excessive supplementation of inorganic zinc brings serious environmental pollution
due to low utilization.
› Thus, broilers and breeders fed diets containing high concentrations of zinc are
potentially producing faecal waste that contains more zinc than field crops can
utilize.
› Today, large scale commercial livestock production system have given rise to many
environmental concerns, since excess mineral concentrations in the manure can
lead to mineral depositions that exceed crop nutrient requirement.

28. Cont. …
› Enhanced bioavailability of mineral source can:
1. Potentially reduce the amount of a mineral that is added to a diet to meet nutritional requirement
2. Reduce the amount of mineral excreted by birds.
› Although organic form of trace minerals have increasingly been used by poultry feed
industry, the use of organic complexes of trace elements such as Zn-lysine and
Znmethionine has received more attention because of their potential for greater
bioavailability.

29. Zn & Egg shell quality

30. Zn & Egg shell quality
› Egg shell quality is one of the most important problems in poultry industry,
influencing economic profitability of egg production and hatchability.
› High egg shell breaking strength and lack of shells defects are essential for
protection against penetrating bacteria into the eggs.
› One of the main concerns is the decrease of egg shell quality with hen age, because
the incidence of cracked eggs could even be more than 20% at the end of laying
period.

31. Cont. …
› Most of the studies on nutrition effects on egg shell and bone quality in laying hens
have been focused on macro-minerals (Ca & P) and vitamin D3.
› In addition to this, some enzymes related with some microminerals are important for
mineralization process;

32. Cont. …
1. Carbonic anhydrase
– It is a zinc dependant enzyme that plays a role in converting calcium into calcium carbonate
which is needed for egg shell formation.
– Activity of carbonic anhydrase, an essential enzyme for eggshell formation, has been directly
related to zinc status of hens.
2. Metalloenzymes
– Zinc and manganese, as cofactors of metalloenzymes, responsible for carbonate and
mucoploysaccharides synthesis which implies their importance in egg shell formation.

33. Cont. …
3. Egg shell mechanical properties
› Zinc, copper and manganese could affect mechanical properties of egg shell by
effect on calcite crystal formation and modifying crystallographic structure of egg
shell.

34. Cont. …
Inadequate zinc status of hen may reduce:
1. Egg shell quality
2. Hatchability
3. Embryonic development
4. Poor chicks’ quality