CHAPTER 2: PROBLEMS OF POULTRY PRODUCTION | NUTRITIONS OF FOWL FEEDS | LITERATURE REVIEW



CHAPTER TWO
2.0                                           LITERATURE REVIEW
2.1       Problem of Poultry Production
The problem of protein deficiency in Nigeria is evidenced by the fact that an average Nigeria consumes about l0g per day of the minimum daily protein intake of 35g recommended by Food and Agricultural Organization (FAO, 1997). Ani and Adiegwu (2005) had attributed the low protein intake to low level of animal protein production and high cost of animal products, and suggested the intensification of the production of highly reproductive animals with short generation intervals such as poultry, pigs and rabbits (Fielding, 1992; Serres, 1992; Smith, 2001). 

However, the major factor militating against intensive animal production in Nigeria is the high cost of feed and feed ingredients like maize, soybean cake and groundnut cake (Obioha, 1992) The ever increasing cost of poultry feeds with the attendant increase in the cost of chickens and eggs shows that there is need to explore the use of alternative feed ingredients that are cheaper and locally available such as cassava peel meal, bambara nut waste, maize chaff etc.


2.2       Bambara Nut Waste
Bambaranut (Vigna Subterranean (L) verdc) waste is widely cultivated in the Northern and Southern States of Nigeria where the seeds are processed into flour and consumed as moi moi (Enwere 1998). The processing of the seeds into flour results in the production of the waste which contains 16.40% crude protein (Okeke 2000). Bambara nut waste has been used in feeding of poultry and rabbits (Okeke, 2000; Ani and Okafor, 2004; Ani; 2006, Ani; 2008). However, its use in the feeding of monogastric animals is limited by the presence of such anti-nutritional factors, as protease inhibitors, haemoglutinins, tanins, cyanogenic glycosides and flatulence factors in the raw bean (Doku and Karikari, 1981; Esminger, 1996; Enwere 1998).
          Besides antinutritional factors, another limitation is its high fibre content. Poultry cannot fully utilize high fibre diets because they lack the digestive framework that can elaborately digest large amount of fibre. It becomes imperative, therefore, to incorporate exogenous enzymes into their diets in order to enhance the breakdown of the non-starch po!ysaccharides (NSPs) present in fibre.

2.3       Production and Nutritional Value of Roots and Tubers (Cassava)
            Cassava is cultivated as staple food crops. They are efficient in producing cheap food energy. More than 228 million tons of cassava was produced world wide in 2007, of which Africa accounted for 52%. In 2007, Nigeria produced 46 million tons making it the world’s largest producer (Table 1). The yields of sweet potato was 15-20 tonnes per hectare and cocoyam give 25-30 tonnes per hectares of corms depending on planting density
Table 1:          Nutritional value of roots and tubers (cassava) in different
countries                                                       
Year
Countries                              2006               2007               2008*             2009**
Nigeria                                   45721             34410             42770             45000
Congo, Dem Rep. of 14989             15004             15020             15036
Ghana                         9638               9650               9700               10000
Angola                                   8810               8800               8900               9000
Mozambique                         6765               5039               8400               9200
Tanzania, United                  6158               6600               6700               6500
Rep. of                                   6158               6600               6700               6500
Uganda                                   4926               4456               4942               4500
Malawi                                   2832               3239               3700               4000
Madagascar                           2359               2400               2405               2000
OtherAfrica                           15,251            15,354            15923             16233
Africa                                     117                 104                 118                 121469
449                 952                 461
Latin America                       36311             36429             37024             36606
Asia                                        70465             75882             77631             83715
World                                     224                 217                 233                 242069
483                 536                 391
           
            The roots, tubers and their by-products are valuable sources of nutrients (Table 2). They share a number of nutritional characteristics that constitute serious limitations for their practical use in poultry, pig and fish feeding, if they are compared with the cereals which are feed ingredients. The most important of these limitations are as follows:
i.                    All of them are succulent materials with low content of dry matter (25-32 percent).                                                  
ii.                 This makes the preservation, transport costs and general handling more difficult.
ii.         All of them have starch being the major component with low protein (2.7-7.9 percent) that obviously needs adequate protein supplementation
iii.       Root and tuber by-products (peels, leaves and vines) are high in crude fibre (12.1-16.0%). With such high level, the use of appropriate exogenous enzymes to degrade the fibre is required for improved utilization by non ruminants (Longe, 2006)
iv.        Some of them contain toxic/anti nutritional factors (Table 3) such as cyanogenic glycosides (lineation and lotaustralin) in cassava which cause bitter taste and reduce palatability of the roots. Cocoyam contains irritating/ acidity substance that causes burning sensation. The undesirable substances must be eliminated through some kind of processing such as fermentation, grating, boiling or sun-drying before being fed to animals to reduce the risk of toxicity.
v.         Microbial contamination due to high moisture content. Sun-drying of these materials in a humid environment, especially during a bad weather, results in the proliferation of microbial organisms in the feed materials. It is imperative to have driers and silos to reduce deteriorative changes and contamination.
vi.        Dustiness of the dried roots and tubers flour can cause irritation of the respiratory tract unless feed is pelletized or palm oil is added.

2.3.1 Anti Nutritional Factors
Foods are complex substances that contain many chemical compounds, many of which are required to nourish the body. These nutrients include water, protein, lipid, carbohydrate, minerals and vitamins. Most plant foods consist of natural compounds or anti-nutrients that appear to function generally in defense against herbivores and pathogens. Anti-nutrients are potentially harmful and give rise to a genuine concern for human and animal health in that they prevent digestion and absorption of nutrients. They may not be toxic as such, but can reduce the nutritional value of a plant by causing a deficiency in essential nutrients or preventing thorough digestion when consumed (Prathibha et al., 1995). The most commonly known and studied anti-nutritional factors in roots and tubers include cyanogenic glycosides, saponin, phytate, oxalate, enzyme inhibitors and total alkaloids (Table 3). They must be inactivated or removed before they are suitable for non ruminants or fish (Bhandari and kawabata 2004; Agbor-Egbe and Mbome 2006).
           The cyanogenic glycosides or cyanogens are glycosides of 2-hydro xynitriles that are synthesized and stored in cassava and are widely distributed among plants (Rosenthal and Berenbaum 1991; Bisby et al, 1994). The peel component has the highest concentrations of cyanogenic glycosides in cassava (Table 3). In cocoyam tubers, Abdulrashid and Agwunobi (2009), Olajide et al., (2011) reported wide variation (2.10-11
17.13mg/bOg) in the level of these undesirable substances. Hydrolysis of cyanogenic glycosides releases hydrogen cyanide (HCN), which inhibits several enzyme systems, depress growth through interference with certain essential amino acids and utilization of associated nutrients (Tewe and Egbunike 1992, Okafor, 2004). Cytochrome oxidase is the primary site of action for ingested cyanide, an effective inhibitor of many metalloenzymes (Enneking and Wink, 2000).
The enzyme cytochrome oxidase in the mitochondria of cells is inactivated by hydrogen cyanide binding to the Fe2+/Fe3+ contained in the enzyme. This results in a reduction of oxygen usage in the tissues (Vetter, 2000) and oxygen starvation at cellular level, due to the effects of cyanide poisoning, resulting in death. Respiratory failure is therefore the cause of death since the respiratory centre nerve cells are extremely sensitive to hypoxia (Okolie and Osagie, 1999). Other diseases associated with dietary cyanide intake include (1) Konzo Cliff et al., (1997), a paralytic disease; (ii) tropical ataxic neuropathy (TAN) Onabolu et al., (2000), a nerve damaging disorder that renders a person unsteady and uncoordinated: (iii) goiter and cretinism (Delange et al., 1994). (Sheeba and Padmaja, 1992; Okafor, 2001) observed that the palatability and shelf life of cassava products may be prolonged by processing. The levels of cyanogenic glycosides and hydrogen cyanides are also reduced to safer limits by processing (peeling, slicing, boiling, fermentation) before consumption (Sheeba and Padmaja, 1997, Feng et al., 2003).

Table 2:         Composition of roots, (% dry matter) tubers, their by-
products and cereals
Roots tubers and
Dry matter
Cruse protein
Crude fibre
Fat
Ash
Starch
Gross energy
(kcal/kg)
Cassava root
31.90
2.70
3.10
0.80
3.70
76.5
3909.40
Cassava root ensiled
43.50
2.00
2.90
0.50
3.4
74.10
3010.18
Sweet potato tuber
30.10
2.50
1.53
0.60
1.0
72.40
4061.00
Cocoyam tuber
24.90
7.90
1.90
0.70
5.20
77.9
3474.60
Root and tuber by products







Cassava peel (dry)
94.90
8.20
12.50
3.40
5.40
-
2460.00
Sweet potato vines (dry)
86.60
23.10
16,00
5,30
4,02
-
2269.58
Cassava leaves (dry)
92.20
29.00
14.90
6.70
11.6
-
2532.37
Cocoyam leaves
8.20
20.60
12.10
11.70
12.10
-
2314.60
Cereals







Maize
87.0
10.0
1.3
4.0
2.0
71.8
4096.5
Guinea corn
88.4
9.9
2.9
2.4
2.1
74.6
3940.9

Apata et al., 1999, Bradbury and Nixon 1998, Oyenuga 1968, Olajide et al., 2011.


Table 3:         Symptoms and Mode of Elimination of Toxic
Components of Roots, Tubers and their by-products
Roots, tubers and by-products
Toxic/anti-nutritional factor
Typical levels
Primary assistant symptoms
Mode of elimination
Fresh cassava root
Hydrocyanic acid
233-1150(mg/kg DM)
Vomiting, dizziness
Fermentation, boiling
Fresh cassava peel
Hydrocyanic acid
1300-2250(mg/kgDM)
Vomiting, dizziness, diarrhea, death
Sun-drying.
Dried cassava root
Hydrocyanic acid
14-65(mg/kg DM)
Vomiting, dizziness, diarrhea, death
Sun –drying
Dried cassava waste
Hydrocyanic acid
57.2(mg/kg DM)


Fresh cassava leave
Hydrocyanic acid
2650-7200(mg/kg DM)


Cocoyam tuber
Irritating/acidity substance
-
Irritation/burning sensation
Cooking heating and fermentation
Apata et al., 1999, Olajide et al., 2011, Nwokolo 1990a, Tewe et al.,1976.

              Phytic acid, which is hexaphosphate of myo-inositol, is very common in the plant kingdom (Chan et al., 2007). Phytic acid is the primary storage compound of phosphons in plants, accounting for up to 80 percent of the total phosphorus (Raboy, 2001, Steiner et al., 2007). Phytic acid has been found in cassava root (Panigrahi et al., 1992) and cocoyam tuber (Olajide et al., 2011) up to levels of 62.4 and 1.75g/l00g respectively. (Josefsen et al., 2007) reported to the negatively charged phosphate in phytic acid strongly binds to metallic cations (e.g. Ca, Fe, K, Mg, Mn and Zn) and forms a mixed salt called phytin or phytate.
Phytate forms insoluble complexes because they are negatively charged under physiological conditions. These complexes cannot be digested or absorbed in the gastrointestinal tract of monogastric animals owing to the absence of the intestinal phytase enzyme (lgbal et al., 1994). Deficiencies of phosphorus and nutritionally important minerals in monogastric animals can be as a result of cations bound in the phytic acid salt and of low bioavailability of phosphorus (Apata and Olog hobo 1989).
2.3.2 Use of Cassava in Diets for Poultry
              Poultry feed constitutes more than 90 percent of all commercial livestock feeds produced. The use of cassava as a substitute for maize will therefore make its greatest impact if it can be incorporated into commercial poultry feeds. Certain precautions need to be taken to achieve satisfactory performance of stock on cassava based diets. These include removal of cyanide, higher protein supplementation with fish meal, soybean, groundnut cake or methionine in its pure form and the prevention of microbial activity during sun-drying as well as overcoming dustiness. Most of the present studies indicate that satisfactory growth response has been obtained for growing chicken at 10% incorporation of cassava flour (lafun) or cassava peel into the diet: 40% inclusion of cassava flour or 20% inclusion of cassava peel in layer’s diet is satisfactory for egg production (Tewe and Egbunike, 1992). Combination of cassava root and leaves in ratio 4:1 could replace maize in poultry diets and reduce feed cost without a loss in weight gain or egg production (Tewe and Bokanga, 2001). Feeding cassava chips supplemented with Moringa Oleifera leaf meal at5% and 10% levels showed that cassava chips replacing maize at 55-56 and 83.33% in the diets of broilers had no negative effect on productivity and hematology (Olugbemi et al., 2010).
2.3.3 Use of Cassava Peel in Poultry Diets.
Cassava peel can be used to cut down the cost of production and lead to an active and sustainable development in livestock production (Olorede et al., 2002). Some workers (Osei and Duodu, 1998; Agunbiade et al., 2001; Salami et al., 2003) recommended the inclusion of fermented cassava peel up to 15% in broiler diets with no adverse effects. For a reasonable performance of animals fed cassava-based diets, the rations must be nutritionally balanced and with protein source that contain sufficient sulphur-containing amino acids (Tewe, 1992).
             In the study on the influence of protein source on the performance and hematology of broiler chicken on cassava peel-based diets using fishmeal and groundnut cake, Egbunike et al., 2009) reported that broilers could be raised on cassava peel-based diets using groundnut cake as protein source without any adverse effect on performance indices. Also, Sogunle et al., (2009) studied the inclusion of cashew nut reject and cassava peel meal in the diet of growing pullets and concluded that combination of 10% cassava peel meal and 30% cashew nut reject meal was appropriate for enhanced performance of growing pullets.
2.3.4 Precautions in using Cassava as Poultry Feed stuff
Although there is presence of a cynogenic glucoside, which on hydrolysis yields the poisonous HCN, results from various studies have shown that this could be removed to tolerable levels by adopting different processing methods (lgwebuike and Okonkwo, 1993). Udedibe et al., 2000) reported no deleterious effect utilizing sun-dried cassava tuber based ration for egg and broiler productions. (Oke, 1996; Nweke and Ezuma 1998) reported that sun-drying, heating and or soaking in water for 3-5 days eliminated 80-95% of cyanide in cassava.
2.4 Maize Chaff
Maize is a cereal crop that is grown widely throughout the world and generally consumed by Nigerian’s than any other grains (IITA, 2009). It can be eaten after cooking or smoking and can also be converted into animal feeds. The wastes of maize which are left behind after harvest include the hooks, chaff, stocks and the leaves (Oseni and Ekperigin 2007). Maize chaff constitute of 25.55% moisture content, 1.03% ash, 3.72% fibre, 0.61% protein, 1.48% fat and 75.85% carbohydrate (Oseni and Ekperigin 2007).

2.5 Nutrient Requirements of Poultry
For maximum growth and good health, intensively reared poultry need a balanced array of nutrients in their diet. The nutrients required by birds vary according to species, age and the purpose of production.
Whether the birds are kept for meat or egg production (Lesson and summers 2001). Table I provides a summary of recommended minimum levels of selected nutrients for meat chickens of different ages and for layers. To meet these specific needs, different classes of poultry have to be fed different types of diets (NRC 1994). These recommendations should only be considered as guidelines and used as the basis for setting dietary nutrient concentrations in practical diets. Historically, recommendations on nutrient requirements have been based on available literature and data from expert groups (NRC 1994), currently, however, because each specific genotype has it’s own requirements, most commercial feed formulations use minimum requirements recommended by the breeding companies that supply the chicks.
             Poultry require nutrients to maintain their current state (Maintenance) and to enable body growth (weight gain) or egg production (Leeson and Summers, 2005). Birds need a steamy supply of energy, protein, essential amino acids, essential fatty acids, minerals, vitamins and, most important water (NRC, 1994). Poultry obtain energy and required nutrients through the digestion of natural feedstuffs, but minerals, vitamins and some key essential amino acids (lysine, methionine, threonine and tryptophan are often offered as synthetic supplements (Scanes et al., 2004).

Table 4:         ecommended Minimum Nutrient Requirements of Meat
Chickens and Laying Hens, as Percentages or Units per Kilogram of diet (90 percent dry matter).



Meat chickens

Laying hens
Nutrient Metabolizable energy
Unit kcal/kg mj/kg(%)
0-3 weeks 3200 13.38
3-6 weeks
3200 13.38 20
6-8 wks
3200 13-38 18
2900 12.13 15
Amino acids
%




Arginine
%
1.25
1.10
1.00
0.70
Glycine + serine
%
1.25
1.14
0.97
-
Histidine
%
0.35
0.32
0.27
0.17
Isoleucine
%
0.80
0.73
0.62
0.65
Leucine
%
1.20
1.09
0.93
0.82
Lysine
%
1.10
1.00
0.85
0.69
Methionine
%
0.50
0.38
0.32
0.30
Methionine + cysteine
%
0.90
0.72
0.60
0.58
Phenylalanine
%
0.72
0.65
0.56
0.47
Phenylalanine + tyrosine
%
1.34
1.22
1.04
0.83
Threonine
%
0.80
0.74
0.68
0.47
Tryptophan
%
0.20
0.18
0.16
0.16
Valine
%
0.90
0.82
0.70
0.70
Fatty acid





Linoleic acid
%
1.00
1.00
1.00
1.00
Major minerals





Calcium
%
1.00
0.90
0.80
3.25
Chlorine
%
0.20
0.15
0.12
0.13
Non–phytate phosphorus
%
0.45
0.35
0.30
0.25
Potassium
%
0.30
0.30
0.30
0.15
Sodium
%
0.20
0.15
0.12
0.15
Trace minerals





Copper
Mg
8
8
8
-
Iron
Mg
80
80
80
45
Iodine
Mg
0.35
0.35
0.35
0.04
Manganese
Mg
60
60
60
20
Selenium
Mg
0.15
0.15
0.15
0.06
Zinc
Mg
40
40
40
35
           
National Research Council, 1994.

2.6 Energy Requirement
Poultry can derive energy from simple carbohydrates, fat and protein (Esminger, 1990). They cannot digest and utilize some complex carbohydrates, such as fibre, so feed formulation should use a system based on available energy (Scott 1991). Metabolizable energy (ME) is the conventional measure of the available energy content of feed ingredients and the requirements of poultry. This takes account of energy loses in the faeces and urine (Esminger, 1990).
           Birds eat primarily to satisfy their energy needs, provided that the diet is adequate in all other essential nutrients. The energy level in the diet is therefore a major determinant of poultry’s feed intake (Rose 1997). When the dietary energy level changes, the feed intake will change and the specifications for other nutrients must be modified to maintain the required intake. For this reason, the dietary energy level is often used as the starting point in the formulation of practical diets for poultry (Lesson and Summers, 2005).
          Different classes of poultry need different amounts of energy for metabolic purposes, and a deficiency will affect productive performance. To sustain high productivity, modern poultry strains are typically fed relatively high energy diets (Esminger et al., 1990). The dietary energy levels used in a given situation are largely dictated by the availability and cost of energy rich feedstuffs. Because of the high cost of cereals, particularly maize, the use of low-energy diets for poultry feeding is not uncommon in many developing countries.
2.7       Protein and Amino Acids Requirements
The function of dietary protein is to supply amino acids for maintenance, muscle growth and synthesis of egg protein (Ravindran and Bryden, 1999). The synthesis of muscle and egg proteins requires a supply of 20 amino acids, all of which are physiological requirements. Ten of these are either not synthesized at all or are synthesized too slowly to meet the metabolic requirements, and are designated as essential elements of the diet. The balance can be synthesized from other amino acids; these are referred to as dietary non-essential elements and need not to be considered in feed formulations (NRC 1994). From a physiological point of view, however, all 20 amino acids are essential for the synthesis of various protein in the body. The essential amino acids for poultry are lysine, methionine, threonine, tryptophan, Isoleucine, leucine, histidine, valine, phenylalanine and arginine. In addition some consider glycine to be essential for young birds, because they can be synthesized from methionine and phenylalanine respectively (NRC 1994). Of the ten essential amino acids, lysine, methionine and threonine are the most limiting in most practical poultry diets (Ravindran and Bryden, 1999).
              Poultry do not have a requirement for protein per se. However, an adequate dietary supply of nitrogen from protein is essential to synthesize non-essential amino acids (Scanes et al., 2004). This ensures that the essential amino acids are not used to supply the nitrogen for the synthesis of non-essential amino acids. Satisfying the recommended requirements for both protein and essential amino acids therefore ensures the provision of all amino acids to meet the birds physiological needs. The amino acidrequirements of poultry are influenced by several factors, including production level, genotype, sex, physiological status, environment and health status (Ravindran and Bryden, 1999). For example, high levels of lean meat deposition require relatively high levels of lysine (Scott and Dean 1991). High levels of egg output or feather growth require relatively high levels of methionine (Leeson and Summers, 2001).
             However, most changes in amino acid requirements do not lead to changes in the relative proportions of the different amino acids. There is therefore an ideal balance of dietary amino acids for poultry, and changes in amino acid requirements are normally expressed in relation to a balanced protein or ideal protein (Ravindran and Bryden, 1999).
2.8 Fat and Fatty Acids Requirements
            Because of the greater energy density of fat compared with carbohydrates and protein, poultry diets usually include fats to achieve the needed dietary energy concentration. Fat accounts for about 3 to no more than 5 percent of most practical diet (Leeson and Summers, 2005). Other benefits of using fats include better dust control in feed mills and poultry houses, and improved palatability of diets (Erminger et al., 1990). Poultry do not have a specific requirement for fats as a source of energy, but a requirement for linoleic acid has been demonstrated (Rose, 1997). Linoleic acid is the only essential fatty acid needed by poultry, and its deficiency
has rarely been observed in birds fed practical diets (Leeson and Summer, 2005). Linoleic acids main effect in laying birds is on egg size.
2.9       Mineral Requirement
            Minerals are needed for formation of the skeletal system, for general health, as components of general metabolic activity, and for maintenance of the body’s acid base balance (NRC, 1994). Calcium and phosphorus are the most abundant mineral elements in the body, and are classified as macro-minerals, along with sodium potassium, chloride, sulphur and magnesium. Macro-minerals are elements required in the diet at concentrations of more than 100 mg/kg.
            Calcium and phosphorus are necessary for the formation and maintenance of the skeletal structure and for good egg-shell quality (Scott and Dean 1991). In general, 60 to 80 percent of total phosphorus present in plant-derived ingredients is in the form of phytate phosphorus. Under normal dietary conditions, phytate phosphorus is poorly utilized by poultry owing to the lack of endogenous phytase in their digestive enzyme (Leeson and Summers, 2005). It is generally assumed that about one-third of the phosphorus in plant feedstuffs is non-phytate and is biologically available to poultry, so the phosphorus requirement for poultry is expressed as non-phytate phosphorus, rather than total phosphorus (Leeson and summers, 2001). A ratio of 2:1 must be maintained between calcium and non-phytate phosphorus in growing birds’ diet, to optimize the
absorption of these two minerals. The ratio in laying birds diet is 13:1, because of the very high requirement for calcium for good shell quality
(NRC, 1994).
             Dietary proportions of sodium (Na), potassium (k), and chloride (Cl) largely determine the acid-base balance in the body for maintaining the physiological pH (Leeson and Summer, 2001). If a shift occur towards acid or base conditions, the metabolic processes are altered to maintain the pH, with likely result of depressed performance. The dietary electrolyte balance is described by the simple formula (NA++ K+-Cl-) and expressed as MEq/kg diet (Hunton, 1995). Prevention of electrolyte imbalance needs careful consideration, especially in hot climates. Under most conditions, a balance of about 250mEq/kg of diet appears satisfactory for optimum growth, (Scanes et al., 2004). The overall balance among these three minerals, and their individual concentrations are important. To be effective, the dietary levels must each be within acceptable ranges, not deficient and not excessive. Birds exposed to heat stress consume more water, and are better able to withstand heat when the water contains electrolytes (Leeson and Summers, 2001). The replacement of part of the supplemental dietary sodium chloride with sodium bicarbonate has proved useful under these conditions (Leeson and Summers, 2001).
            Trace elements include copper, iodine, iron, manganese, selenium, zinc and cobalt, function as components of large molecules and as co- factors of enzymes in various metabolic reactions (NRC, 1994). These are required in the diet in only very small amounts (Table 1). Practical poultry diets should be supplemented with these major and trace minerals, because typical cereal-based diets are deficient in them (Leeson and Summers, 2005). Organic forms of some trace minerals are currently available, and are generally considered to have higher biological availability than inorganic forms.
2.10 Vitamins Requirements
             Vitamins are inorganic substance required in small amount in the diets for maintenance of normal body reactions and health (Olomu, 1995). Consequently the functions of vitamins are enhancement of digestion, absorption, metabolism, maintenance of weight, egg production. Generally, vitamins are classified as fat soluble (Vitamin A, D, E and K) and water soluble (vitamin B complex and vitamin C). All vitamins, except for vitamin C, must be provided in the diet. Vitamin C is not generally classified as a dietary essential as it can be synthesized by the bird (NRC 1994). However, under adverse circumstances such as heat stress, dietary supplementation of vitamin C may be beneficial (Leeson and Summers, 2001). The metabolic roles of the vitamins are more complex than those of other nutrients. Vitamins are into simple body building units of energy sources, but are mediators of or participants in all bio-chemical pathways in the body.
2.1.1 Water Requirements
             Water is the most important, but most neglected nutrient in poultry nutrition. Water has an impact on virtually every physiological function of the bird. A constant supply of water is important to
i.          the digestion of feed
ii.         the absorption of nutrients
iii.       the excretion of waste products and
iv.        the regulation of body temperature (NRC, 1994).
            Water constitutes about 80 percent of the body (NRC, 1994). Unlike other animals, poultry eat and drink all the time. If they are deprived of water for even a short time, production and growth are irreversibly affected (Leeson and Summers, 2001). Water must therefore be made available at all times. Both feed intake and growth rate are highly correlated with water intake. Precise requirements for water are difficult to state, and are influenced by several factors, including ambient conditions, and the age and physiological status of the birds (Scanes et al., 2004). Under most conditions, water intake is assumed to be twice the amount of feed intake. Drinking-water temperatures should be between 10 and 25°C. Temperatures over 30°C will reduce consumption (Leeson and Summers, 2001).
             The quality of water is equally important. Quality is often taken for granted, but poor water quality can lead to poor productivity and extensive
economic losses (Hunton, 1995). Water is an ideal medium for the distribution of contaminants, such as chemicals and minerals, and the proliferation of harmful microorganisms (Rose, 1997). Water quality for poultry can be a major issue in arid and semi-arid regions where water is scarce. In particular, underground water in these areas can have high levels of salt. Saline drinking water containing less than 0.25 percent salt is tolerated by birds, but can cause sodium toxicity if water intake is restricted
(NRC, 1994)
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