III. INTRODUCTION

Poultry has pioneered industrial-scale meat production in most countries.

The small space required, the speed to close the production cycles and the ease of transporting fertile eggs or chicks, have facilitated this industrial implantation. Like any industry, poultry requires the scientific and technological support of various disciplines: genetics, physiology, biochemistry, nutrition, microbiology, immunology.  If we look at the economic aspect, in terms of production costs, the food cost stands out for its percentage incidence.

Nutritional knowledge is necessary to produce chicken meat suitable for human food at acceptable costs. This provides a source of protein that is easily accessible to the majority of the population.

This study on broiler nutrition has been structured according to various aspects. It is initiated by a chapter aimed at exposing the physiology of avian digestion to continue with the study of ingredients used in the production of compound foods, including nutritious compounds and compounds for technological use. The next chapter discovers the basic chemical compounds that the food must provide and displays a table on the needs of broilers at different ages of the cycle.

Those pollutant compounds that have anti-nutritive action are discussed below and the measures to prevent or reduce their effect (formulation program, installations, analysis and technology) are exposed. The deficient states of nutritional imbalance and stressors that can influence food or performance are also discovered and a section is dedicated to the breeding of broilers in grazing. Finally, the study links nutrition to management and pathology and proposes a work plan that includes the method for evaluating the results.

II. PHYSIOLOGY AND DIGESTIBILITY

The digestive system of the broilers and its functioning condition the nutrition of the birds. A brief review of their physiology is necessary to be able to study the practical aspects later.

Birds lack teeth and therefore chewing function. Thus, salivary secretion is scarce and fulfills its lubrication mission. Contains amylase.

From the mouth, the food passes to the maw where it remains a variable time depending on the filling state of the gizzard. The maw has no digestive secretion, but the amylase content of saliva can initiate the digestion of starches and, in general, food is softened. Whole grains can stay 12 hours or longer. After 24 hours, all the food has come out of the maw.

From the maw, food passes through the proventriculus or glandular stomach, where the secretion of gastric juice containing hydrochloric acid and pepsinogen occurs. The first produces the pH drop and activates the conversion of pepsinogen to pepsin that has as its mission the digestion of the protein.

Food and gastric juice pass into the ventricle or gizzard, which is a powerful shredder muscle device coated inside with a yellow cornea layer. In it, food is finally ground with the help of sand or pebbles. It has no secretion, but inside it acts the gastric juice segregated by the proventriculus.

Partially digested foods pass into the small intestine. Composed of duodenum, jejunum and ileum, it receives the pancreatic (duodenal handle) and hepatic secretion (final duodenal handle) and the digestion is performed in its first section.

Pancreatic secretion contains bicarbonate (pH stabilizer), amylase (starch digestion), carboxypeptidase (protein digestion), tri pepsinogen and chemo-tri pepsinogen. The latter two are converted respectively into trypsin and chemo-trypsin by the effect of enteropeptidases segregated by duodenum. Finally, pancreatic secretion contains lipases that digest fats.

Hepatic secretion consists of bile, whose mission is to emulsify fat and stimulate the activity of pancreatic lipase. This aspect of digestion physiology is particularly interesting because the current broiler diets contain high percentages of fat, in order to increase body weight, above the physiological needs of the bird.

Jejunum and ileum secrete maltase and sucrase (carbohydrate digestion), dipeptidases and aminopeptidase (protein digestion) and stearases (fat digestion).

The large intestine of birds has little capacity and no digestive activity. In the cecum, bacterial formation occurs and, in the colon, continues digestion by the enzymes from the small intestine. In contrast, the colon absorbs water just like the cloaca, although this last absorbs water from urine.

From all exposed above, aspects are concluded related to the digestibility of avian foods.

It can be said that lactose and fiber are poorly digested, except bacterial fermentation in the cecum and this lack of digestibility affects all nutrients contained in foods containing lactose or high percentage of fiber. The final broiler food should contain less than 5-8% fiber and has been proven that content above 10% slows growth.

To conclude this chapter, we will point out that the excreta of the broilers are composed of urine residues and intestinal digestion. Urine, once the water is reabsorbed, is expelled in the form of whitish paste. The final faeces are rich in nutrients for other animals, and essentially contain undigested carbohydrates, cecal fermentation products (fatty acids and vitamin B), intestinal wall cells, lysine 0.39%, methionine 0.12%, calcium 7.4% and phosphorus 2.1%.

On this basis, in some countries, broiler excreta are recycled in the feeding of other animals, especially ruminants.

III. INGREDIENTS OF BROILER FEEDING

Ingredients intended for the feeding of broilers can be grouped into:

a) Grains and by-products

b) Protein ingredients of animal origin

c) Protein ingredients of vegetal origin

d) Fats

e) Phospho-calciumminerals

f) Premixes that provide vitamins and microminerals

g) Technological premixes

h) Other ingredients

a) Grains and grain by-products:

These are high-carb foods that provide, essentially, energy. In general, they are poor in protein, calcium and phosphorus. In poultry, maize, wheat, sorgo and rice are the most widely used. The total mixture of all of them and their by-products ranges from 45-75% of the starter food and between 60-80% of the growing broiler food with a minimum of 40-60% grain.

b) Proteiningredients of animal origin:

These are foods rich in protein, calcium and phosphorus. They may contain varying amounts of fat depending on the production process and raw material. In poultry are widely used meat meal 50-55% and fishmeal 60-65%, the total mixture of them in the food should not be less than 3-4, 5% although our experience advises its use between 7-8%. Flour from the species itself is not usually used.

c) Proteiningredients of vegetal origin:

These are foods rich in protein, but poor in calcium and phosphorus. In poultry, deactivated whole-grain soybeans, extracted soybeans, peanut cake and corn gluten are used. The content of the compound food in these ingredients can range from 18-25% in initiation and around 17-21% in growing broilers.

In periods of shortage of meat or fish meal, these plant ingredients can be substituted between 50 and 100% provided that calcium, phosphorus and some amino acid deficiencies are taken into account and a good supply of vitamins is available.

A vegetable protein ingredient can be replaced by another and a part of meat meal or fish meal.

d) Fats:

They are necessary in avian feeding in minimum amounts of 2-3%. In general, the intake of up to 5% fat can be considered as an energy supply. Amounts ranging from 5 to 10%, i.e. an additional 5% over the minimum, are destined by the body to be deposited. In this way, 50 g of fat per kg of food consumed is converted into 50 g of body weight.

However, there is a limit: above 10% total fat significantly increases the deposit of lipids in the circulatory system and, with the deposit, increases the risk of death. In this way, the benefits of weight gain are countered by the mortality of heavier broilers.

On the other hand, broilers fed with low fats may have fatty deposits of high melting point from excess carbohydrates.

In poultry, the most commonly used fats are those from animal origin, vegetable fats and oleins. Fats of animal and plant origin are more stable in their composition, while oleins are very variable in their composition since they are not a product of own manufacture, but the by-product of the processes of production of vegetable oils. In fact, even the olein name isn’t correct. By definition, olein is a chemical compound; oleic acid glyceric ester. By extension, oleins are a mixture of glyceric esters of numerous fatty acids: oleic, linoleic, palmitic and others. This lends itself to mixtures including animal and fish fats.

In general, high melting point fats are less digestible for birds than those with a lower melting point.

e) Phospho-calciumminerals:

They essentially provide calcium and phosphorus. Calcium carbonate, bicalcicum phosphate, bone meal, ground limestone and oyster shell are used in poultry. When using any natural source of phosphorus should be considered its fluoride content, as it can be toxic and should not be contained in avian foods above 0.015%.

It is desirable that the food contain between 1-2% of phosphocalcic minerals although the quantity and the ingredient will depend on the use of meat meal (Ca 8%, P 4%) and fishmeal (Ca 5%, P 2%).

f) Premixesthat provide vitamins and microminerals:

They are called vitamin-mineral correctors. Designed without taking into account the possible contents of such components that could provide the other ingredients of the food.

For broilers, three types are usually used (one per breeding stage): 0-20 days, 20 days to 5 days to the end and one for the last five days. They are incorporated in variable quantities of 0.25 – 0.5% according to the manufacturer’s concept. This should take into account that the incorporation below 0.2% does not guarantee a homogeneous mixture of the concealer with the food, except its incorporation into premix.

On the other hand, it will consider that over-concentrated concealers can allow the contact of vitamins and minerals with the consequent loss of potency of the former.

For a certain poultry production sector, it is necessary to use macro correctors, that is, those that incorporate, in addition to vitamins and microminerals, the phospho-calcium minerals.

The improvement of scientific knowledge and the genetic improvement of broiler lineages require the review and updating of the composition of such premixes. The incorporation of biotin and pyridoxine (B6) are significant examples of this evolution of broilers correctors. Our experience in high productivity lines is to exceed by 10% the international needs tables.

g) Technological premixes:

These are composed of non-nutritive matter but whose main action is to influence animal production. Since their use is continuous, they can create waste in meat and influence public health. For this reason, legislation has been developed that regulate their use, dosage, target species and suppression periods.

Allowed premixes and of poultry interest can be classified into: growth promoters, antioxidants, coccidiostats, pigmenting, preservatives, binders.

Both growth promoters and coccidiostats and pigmenting tend to be incorporated into vitamin-mineral correctors:

1. Growth promoters

   Within the concept of “growth promoters” we can include some antibiotics and intestinal conditioners, which act by different mechanisms. Thus, while antibiotics control bacterial flora, attached to the aging intestinal mucosa, intestinal conditioners regain the physiological rhythm of renewal of enterocytes. Thus, maintaining a young intestinal mucosa there is no bacterial adhesion and antibiotics are not necessary. Bacitracin, spiramycin, virginiamycin, flavophospholipol and avoparcin are some of the antibiotics still allowed in certain countries, although the general trend is to remove them from animal nutrition.

2. Coccidiostats

   Are used in the prevention of coccidiosis and not in their healing.  In this group we can include chemical coccidiostats and intestinal optimizers. Amprolium, associated with methylbenzoquate, dicoquinate, sodium monensin, robenidine, aprincoid, lasalocid, halofuginone, narasine, salinomycin and nicarbacin are some of the coccidiostats still allowed in certain countries, although the general trend is to eliminate them from animal nutrition.

3. The pigmenting

   Are used exclusively for the purpose of presenting the broilerin a manner appropriate to market requirements. In broilers it is allowed to use capsanthin, lutein and its related molecules. Other dyes may be incorporated into the broilers’ food from some ingredient that has been marked by the use of such substances (blue, bright green, tartrazine), such as microtracers.

   Contrary to the three groups described so far, other technological premixes are used directly in the manufacture of broiler food: antioxidants, preservatives, binders and mycotoxin binders.

4. Antioxidants

   Are used to ensure the maintenance of the quality of fats and vitamins incorporated into the food. In broilers the use of ascorbic acid and its derivatives, tocopherol and its derivatives, propyl gallate, octyl and dodecyl, BHA, BHT and ethoxyquin are permitted. The last three are the most used at doses not exceeding 150 ppm of food.

5. Preservatives

   Are used to prevent foodalteration by the effect of microorganisms (bacteria and fungi). Therefore, they also serve to prevent food from becoming transmitters of diseases especially mycosis, salmonellosis and clostridiosis.

   In poultry it is allowed the use of organic acids and cimenol that act against bacteria and fungi present in grains and food, although its mechanism of action is different.

   Thus, organic acids temporarily inhibit the metabolism of microorganisms (they are therefore bacteriostatic and fungistatic) by decreasing the internal pH after entry, in ionized form, through the membrane; while cimenol definitively inhibits the synthesis of a membrane component (it is therefore fungicide and bactericidal).

   Not all acids work equally with all microorganisms. Thus, propionic acid is more effective against gram-negative germs, fungi except Penicillium. In contrast, ammonium propionate has better activity against Penicillium and Salmonella.

   Ammonium formate is effective against gram-positive, negative bacteria and yeasts.

   In general, better efficacy against Salmonella has been reported in acids with fewer number of carbons in their molecule. Synergistic, additive and antagenic effects are also known among preservatives.

   *The use of preservatives can also be done through drinking water as controllers of pathogenic intestinal flora. In this regard they perform a substitute function of food antibiotics with the advantage, if they are organic acids, that they do not create residues in tissues.

   *Its use is necessary according to climate and humidity of the food from:

   12% humidity in warm climates

   13% humidity in temperate climates

   14% humidity in long-term storage climates

6. The binders

   are substances used in the processing of granulated foods. This action itself has no interest since the use of granulated foodif noble ingredients are used. On the contrary, granulation allows the incorporation of by-products whose digestibility is not always the appropriate.

7. Mycotoxin binders

   are carbon or silica polymers that fix mycotoxins in the gastric and ruminal acid medium, but none do so in the food.  There are different fixing mechanisms, although the molecules that act by establishing hydrogen bridges are the safest. It is important to know the ability to fix and the percentage of absorption in the different intestinal sections to decide the most suitable binder and recommended dose.

   This action is performed by establishing hydrogen bridges and is effective in aflatoxin B1, B2, G1, G2, sterigmatocistin, ochratoxin, fumonisins, zearalenone and tricotecenes.

   In broilers is permitted the use of silica, kieselgur, calcium silicate, sodium and aluminum silicate, bentonite, vermiculite, Silicoglycidol and Polysilycol. However, not all of them have efficacy as mycotoxin adsorbents.

8. Pronutrients

Pronutrients are organic molecules from plant extracts, able to stimulate gene expression and regulate physiology without having a pharmacological effect. They leave no residue and do not require withdrawal period.

It is important to differentiate pronutrients from drugs: A drug is a molecule that modifies the action of a protein while a pronutrient is a molecule that stimulates protein production.

For this reason, a pronutrient is considered a substance included within the physiological mechanisms of animals and a drug is a foreign substance to these mechanisms.

They are molecules derived from shikimic acid, a molecule that only plants are able to synthesize. Shikimic acid is the precursor of different biosynthetic pathways of aromatic metabolites such as lignin, flavonoids, alkaloids and quinonones or folates, which play an important role in animal physiology.

Pronutrients were described by Dr. Gordon Rosen in 1950, defining them as micro-ingredients included in the food in relatively small amounts that aim to improve animal physiology, intrinsic nutritional value and avoid the presence of pathogens.

In nature, animals ingest small amounts of different plant sources that provide these active ingredients, however, in animal production, access to these plant sources is restricted, which, together with the stress they are subjected to, makes them much more susceptible to disease. The inclusion of pronutrients in the diet improves normal physiological functioning.

8.1 Mechanism of action

Pronutrients work by modulating gene expression, increasing mRNA synthesis. Increased mRNA synthesis leads to increased production of functional proteins at the cellular level, resulting in improved organic functioning.

8.2. Trials

To check the mechanism of action of the pronutrients, different trials have been performed using cultures of enterocytes and other cells such as hepatocytes and macrophages. The expression of intestinal markers using SUnSET-protein and RNA seq-mRNA techniques, intestinal permeability by forming narrow epithelial joints or Tight Junctions (FITC permeability) and nutrient absorption have been studied.

• Study of intestinal markers: SUnSET-proteintechnique

It is a non-isotopic technique, which was used to understand the effect of pronutrients on translation rates of mRNA into protein. The technique is based on the use of Puromycin, structural analogue of tyrosil-tRNA, incorporated in new proteins through a non-hydrolysable peptide bond.

The binding of puromycin results in the termination of peptide elongation and leads to the release of the peptide attached to the truncated puromycin of the ribosome. Therefore, the measurement of puromycin, through an anti-puromycin antibody (western blot-ELISA) can be correlated with the translation rate of mRNA into protein. Depending on the target cells of the pronutrients stu died, different in vitro models were used:

• EnterocytesIPEC-J2:

  IPEC-J2 cells are grown in DMEM/F-12 mix (MixDulbecco’s Modified Eagle Medium, Ham’s F-12) supplemented with HEPES, Fetal Bovine Serum (FBS) or Pig Serum (PS), Insulin/Transferrin/Selenium (STIs), Penicillin/Streptomycin and grown in a 37oC with 5 % CO₂. The medium was changed every other day and passes were made every 4-5 days.

• Hepatocytes:

  Dulbecco’s modified Eagle medium, nutrient mixture F-12 (Ham) (1:1) with GlutaMAX™-I (DMEM/F12) supplemented with 20% bovine fetal serum. Wet atmosphere with 5% CO₂ at 37°C. Passes were made until a cell density of 2×10⁵/ml was obtained with 5 ml of fresh medium, in culture plates of 25 cm2, every 4 days.

• Alveolar macrophages 3D4/2:

  Dulbecco’s modified Eagle Medium, blend of nutrients F-12 (Ham) (1:1) with GlutaMAXTM-1 (DMEM/f12) supplemented with 20% fetal bovine serum. Wet atmosphere with 5% CO₂ at 37°C. For amplification passes up to a density of 2×10⁵ ml were made with 5 ml of fresh medium in culture plates of 25 cm², every 4 days.

Procedure

The trials were carried out on 12-well plates, where 1.2 x 10� x cells/ml were added in 2 ml volume per well. After 4 days of cultivation, confluence was reached and the culture medium was replaced and supplemented with pronutrients following the scheme described below:

After applying the treatments, the cells were recovered and the crude protein extracts were obtained. The crude protein concentration was measured and equal sample quantities were separated using SDS PAGE. After electrophoresis, the proteins were transferred to a nitrocellulose membrane and immunotransfer assays were performed using Kerafast Anti-puromycin antibodies [3EH11] as a primary antibody and a secondary antibody marked with HRP anti-mouse.

Results

An increase in mRNA synthesis was observed in treatments with different pronutrients compared to control treatments.

• Study of intestinal markers: RNA seq-mRNA

As a next step in the characterization of the mechanisms underlying the effects of pronutrients, it was analyzed which proteins had increased their expression in the treated enteritic cells (IPEC J2).

To do this, the total RNA of the intestinal epithelium cells (IEPC) untreated and treated with pronutrients was obtained, a differential expression analysis was performed using RNA-seq and its subsequent bioinformatic analysis.

Process

The trial was performed on six 6-well plates, where 1,2×10â�µ cells/ml were added in a volume of 3 ml per well. After 4 days of growth, the confluence was reached and the culture medium was replaced and supplemented with a pronutrient-based product (1:10000) on three plates, while the other three plates were used as untreated negative controls. After 60 minutes of exposure, the medium was removed and the RNA was extracted directly using a mixed trizol-column protocol.

The integrity of RNA samples was verified in undenatured agarose gels through Bioanalyzer. The six samples that showed the best integrity and purity scores were chosen for the construction of a complete transcriptomic library.

Statistical analysis of the results was performed using a heat map and a volcano graph.

Results

In cells treated with pronutrients an increased expression of genes related to immune response and metabolism was observed. It was increased the expression of genes associated with cell-to-cell adhesion, cytokine receptors (IL10, IL17) and defensins of the BPI family, as well as the production of exosomes that increase the presentation of antigens. An increase in expression was also observed in the CCDC85B gene, which inhibits cell proliferation, as well as genes related to three types of chitinases, glucosidase and proteins involved in the transport and metabolism of lipids and amino acids.

• Expression of intestinal markers: Formation of epithelial narrow joints or Tight Functions (FICT permeability)

A critical function of the intestinal epithelium is to form a barrier that prevents the penetration of pro-inflammatory molecules, such as pathogens, toxins and antigens, from the luminal environment to the mucosal and circulatory system tissues.

Epithelial or occludens zonule (OZ) are the key structures that regulate paracellular traffic for macromolecules. Alteration of the OZ intestinal barrier induces a disturbance of the immune system of the mucosa and inflammation.

Procedure

IPEC-J2 enterocytes were sown in Transwell inserts, with a collagen-coated membrane, a pore size of 0.4 microns. and a membrane diameter of 6.5 mm (Corning, NY, USA), at a density of 5 x 10⁵/ml, growing for 21 days until confluence. Every three days a new cell was added.

The monolayers were treated with intestinal conditioning pronutrients 1:10000 for 90 min and then the pass of FICT from apical (1 mg/ml) to the basolateral medium was measured.

The analysis of the results was performed using fluorimetry (Biotech Sinergy TH).

Results

Results showed how the application of intestinal conditioning pronutrients in intestinal epithelial cells reduces paracellular permeability. This way, pronutrients allow to reinforce the integrity of the intestinal barrier by protecting the animals against enteric pathogens, food antigens and physicochemical tensions caused by digestive and microbial products, improving animal health status and production parameters.

• Nutrients absorption study: Vitamins

A trial was conducted in order to learn about the effect of pronutrients on vitamin absorption. The increase in absorption of these micronutrients is of great importance since they are what have the highest cost within the formulation

Procedure

The test was carried out on 9-well plates, where 1,2 x 10� cells/ml were added in a final volume of 3 ml per well. After 4 days of growth the confluence was reached and the medium was replaced by a supplemented medium with pronutrients in 6 plates. The remaining 3 plates were used as negative controls.

After 60 minutes of exposure to intestinal conditioning pronutrients (Alquernat Nebsui), the medium was replaced by HBBS (3 wells/plate). After 90 minutes, the cells were washed and smoothed, and the intracellular concentration of vitamin B₁₂ (cobalamin) was measured by a colorimetric assay.

The colorimetric method used is based on the decomposition of vitamin B�₂ by HNO� followed by the subsequent formation of a stable complex with color (λ max 435nm) between the released cobalt ion and the Nitrous-R salt.

Results

Following the trial, it was observed that when pronutrients are co-administered together with vitamin B₁₂ 5micromM, intracellular levels of the vitamin are increased by 30% compared to the control treatment

In view of the results obtained we can say that treatment with pronutrients allows to increase the absorption of exogenous vitamin B₁₂ and, therefore, allows to reduce its levels of inclusion in the feed reducing the productive costs

The same trial was also carried out with other water-soluble vitamins, with fat-soluble vitamins and with amino acids, obtaining the following absorption increments:

Vitamin B1: 56%

Vitamin E: 39%

Vitamin A: 43%

Vitamin D3: 15%

Lysine: 158.6-175.9%

Tryptophan: 113.8-114.2%

Lutein: 33-42%

8.3. General conclusions

• Pronutrientsinduce mRNA-protein translation rates in target cells.
• A higher rate of mRNA-proteintranslation correlates with an increase in the production of specific proteins and therefore better target organ performance.
• In the case of the gut, a key organ in animal production, pronutrientsreinforce the integrity of the intestinal barrier and protect animals against enteric pathogens, food antigens and physicochemical stresses caused by products improving the health status of animals and productive parameters.
• This improvement at the physiologylevel leads to better yields due to better feed conversion rates and lower mortality.

The most important pronutrients in animal nutrition are:

• Intestinal optimizers
• Intestinal conditioners
• Hepatic conditioners

1. Other ingredients: That are used in broiler feeding and that we have grouped in this last section:

1. Sodiumchloride is used in various quantities depending on the percentage of meat and fish meal used in the food and the degree of salinity of the drinking water. Final salt content must be 0.5- 0.6%.

2. Digestive enzymes are used to improve the digestibility of foods that incorporate a large amount of the same cereal, by-products or cereals that contain some undigestible component for broilers such as barley.

The most used enzymes in poultry are β-glucanases, araboxylase, cellulase and phytase.

3. Probiotics are mixtures of living germs that are used to colonize the digestive system of birds with the missions of producing lactic acid, producing enzymes that improve digestibility and occupy the space that otherwise would occupy the flora of pathogenic fermentation.

Current proposals include the use of microorganisms of the following genre: Aspergillus, Bacillus, Bacteroides, Bifidobacterium, Lactobacillus, Leuconostoc, Pediococcus, Propionibacterium, Streptococcus, Sacharomyces, E. coli, Kluveromyces and Selenomonas ruminantium.

We have proposed the incorporation of Candida, Clostridium, Mucor, Rhizopus, Penicillium and Trichoderma.

4. Essential amino acids: In avian feeding are lysine, methionine, tryptophan, phenylalanine, histidine, leucine, isoleucine, valine and threonine and other amino acids important for broiler(arginine, cystine, glycine) are usually present in sufficient quantity in the ingredients

IV. NUTRIENTS AND NEEDS

From the ingredients mentioned in the previous section, feed can be made that provides the nutrient chemical elements suitable for the development of broilers:

Protein:

Has lost value as a general indication. It is necessary to know the total and digestible protein, since, from its difference, is obtained the unusable protein that can be fermented in the intestine and in the litter and therefore the origin of pathogenic processes. In the nutritional aspect the requirements in protein should be replaced by the requirements in essential amino acids and by the relationships between other non-essential: methionine + cystine, phenylalanine + tyrosine and glycine + serine.

Energy:

It’s a very important concept. Some of the energy provided is devoted to the maintenance of vital activities and another is consumed in growth. This should be related to the intake of protein and macrominerals. The imbalance will result in delays: in growth, consumption alterations and changes in channel performance.

Fats:

It is important as an energy input and as a source of fatty acids that are constituent of broiler fat. The essential fatty acids are polyunsaturated: linoleic, arachidonic, linolenic and eicosapentanoic (in fish oil).  Some of these acids may be responsible for transmitting flavors from other species to broiler meat. Increasing Vitamin E in food has been shown to be a decisive factor in avoiding this unpleasant effect.

Minerals:

The fundamentals in the diet of broiler are calcium, phosphorus and magnesium for their contribution to the structure of the skeleton. Others such as sodium, potassium, magnesium have an osmotic and homeostatic mission.

Vitamins:

Are classified in two groups: liposoluble and hydrosoluble.

Liposoluble vitamins are A, D₃, E and K. Its absorption is not influenced by the amount of fat in the food. In contrast, its organic deposit is related to the fat content of the food.

Hydrosoluble vitamins are vitamin C, those corresponding to the complex B: B₁ (thiamine), B₂ (riboflavin), B₆ (pyridoxine), PP (nicotinic acid), H (biotin), pantothenic acid, folic acid and B₁₂ (cobalamin).

Under the name “vitamin F” are known the poly-unsaturated fatty acids mentioned above.

The use of vitamin C in broiler nutrition is considered unnecessary, but not so its use in infectious or stress status. The same was true of biotin, but genetic improvement and increased use of wheat-based food rations and meatmeal have been shown that its use is necessary. Vitamin B₆ intake has also been considered unnecessary, but knowledge of deficit processes and the remarkable cardiac effort to which broilers are subjected makes its use advisable.

Taking into account these sections, we can perform the exposure of the table of the broiler needs expressed in percentages or in milligrams or units per kg of food. Amino acids are expressed as a digestible basis and non-total. The following minimums are set for the three ages of the broiler:

V. ANTINUTRITIVE FACTORS: EFFECTS AND CONTROL MEASURES

The presence of xenobiotic contaminants in animal feed is controlled by producers, consumers and health authorities. As a result of these guidelines its negative impact on animal and human health is decreasing.

However, improved analytical methods and increased demands on food efficiency provide a better understanding of food biochemistry and microbiology by producing a new list of pollutants with a negative impact on animal production and health that comes to be added to traditionally known pollutants.

As a previous step to the description of the control methods, it is necessary to list such pollutants and the consequences of their presence in raw materials and feed.

V.1. Biochemical contaminants typical of various raw materials:

• Alpha-galactosides: they are common in beans, sweet lupin, pea. They reduce the degradation of foodin the caecum and give digestive discomfort.
• Vicine: is isolated in the beans.
• Lipoxigenic enzymes: found in soy. They produce bad grain taste.
• Resorcinol: found in rye. It has alkaloid structure with 15 to 23 carbons. Cause decreased appetite.
• Isothiocyanates: are present in rapeseed. They produce rejection of consumption.
• Euric acid: is isolated in rapeseed. It affects growth and increases liverand heart size.
• Sinapine: occurs in rapeseed in concentrations close to 1%. Chemically it is the ester of synaptic acid with choline. Produces rejection of consumption. It is water-soluble and resists desolification. When its level in feed reaches 0.1% it confers fish smell and taste to meatand eggs.
• Antitryptic factors of pea, soy and beans: prevent pancreatic trypsin from acting on protein. The avian organism reacts by hypertrophying the pancreas. Are known the Kunitz and Browman-Brik factors that cause a secondary deficiency of essential amino acids, especially sulphurs.
• Nitriles: found in rapeseed.
• Glucosinolated: found in rapeseed. Progoitrin causes VOT (vinylthioxazoline) by hydrolysis and has antithyroid activity by inhibition of thyroglobulin. Other glucosinolates include gluconapine and glucoprasinapine.
• β-glucans: occurs in oat, barley, rye. They have growth depressant activity and increase the viscosity of intestinal content.
• Antienzymes: it is possible to isolate them in sand, barley. Has anti-nutritional effects.
• Tannins: found in barley, beans and sorghum (especially bird-resistant varieties). They are aromatic phenols. Decrease palatability and hijack methyl groups of amino acids(choline and methionine) during their passage to methyltanic acid.
• Polyphenols: are found in rye. They have anti-nutritional effects.
• Hydrocyanic acid: found in cassava. In feed it should not exceed 50 ppm. Has anti-nutritional effect from secondary deficiency of methionine and iodine. It is released by glycosides called linamarin and lotaustralin by the action of linamarins.
• Saponins: found in soy. They are triterpenoid glycosides, bitter and hemolytic. They are insoluble in organicsolvents and resist desolification.
• Antiphosphatases: isolated in cassava and soy.
• Phytic acid: is isolated in rye, oat and rice. It provides analytical phosphorus, but little bioavailable.
• Accumulation of minerals: such as calciumin meat meal, potassium in molasses (diarrheal effect).
• Alkaloids: are isolated in lupins. Decrease food
• Gosipol: found in cotton cake. In feed should not exceed 20 ppm. Free gosipol is combined with lysine. Produces liverand kidney lesions.
• Unsaturated fatty acids, in fish meals.
• Lecithins: are isolated in soy and wheat germ. They are macromolecules of negative effect on growth.

V.2. Bacterial contaminants

The presence of bacteria in raw materials and compound feed is constant. Food can act as a support or physical transport, but in most cases the food is rich in some essential nutrient in the metabolism of the bacteria. This is one of three conditioning factors that must be met to make the vehiculated microorganism a possible pathogen.

1. a) Nutritional relationship between foodvehicle and microorganism..
2. b) Important numerical presence.
3. c) Enzymatic endowment of the strain.

Among all microorganisms possibly vehiculated through raw materials and food, a selection is produced, in terms of danger, from the three conditions exposed. In this way the potentially more dangerous bacterial contaminants are:

Escherichia coli: It can contaminate food from faeces, but sometimes its origins are initially apathogenic strains used as probiotics. Current legislation limits its number to absence in 0.1 g. We consider those strains enzymatically endowed with hemolytic capacity and producer of SH₂ to be potentially more pathogenic. Its presence can cause digestive and respiratory disorders.

Salmonella sp.: Some 1300 varieties capable of causing pathogenic processes are known. Serotypes no-pullorum of salmonella similar to typhimurium, enteritidis and heidelberg are etiological agents of many toxin infectious processes.

It can contaminate food from faeces, raw materials made from contaminated by-products, such as flours from animal origin (5%) and cereals (1%).

Current legislation limits its number to absence by 25 g.

Further to its biochemical and serological classification, the mouse pathogenicity test is required to determine its dangerousness.

Its presence does not alter the appearance, smell and taste of food, but can cause digestive, liver and reproductive disorders with impact on the hatchability and onfalithic and joint process of the chick. As we have stated on other occasions, we consider that there are reasonable doubts as to the relationship between the presence of salmonella in raw materials and avian foods with human food poisoning.

These doubts are based on the specificity between host and infecting bacteria, as well as the numerical disproportion between hepatic and reproductive avian processes with cases of human toxin infections.

Other enterobacteria: We make special reference to microorganisms that can often be confused both clinically and microbiologically with salmonella: Proteus and Citrobacter.

Pseudomonas: These multifaceted microorganisms are becoming more common. Its numerical presence is not legally regulated and the enzymatic characteristics most related to its pathogenicity give it hemolytic capacity, producer of SH² and piocyanic pigment.

Clostridium: Its presence in food is very common but the incidence of intestinal clostridiosis is more related to the protein level of the feed than to the number of clostridia in it. In addition to intestinal processing, the production of toxics causes a renal and circulatory picture.

Other sporulated: They can cause diseases similar to clostridiosis especially Bacillus. Its origin, in addition to thermally treated and protein-rich by-products, can be found in some strains used as probiotics.

Staphylococcus: Can be found indiscriminately in any material or food. The enzymatic characteristics that are linked to their pathogenic power are coagulase and thermonuclease positive.

V.3. Fungal contaminants

More than 200,000 species are currently known, but only about 50 are potentially dangerous by themselves or by the development of toxins under certain circumstances of nutrient substrate, temperature and water activity values in raw materials or feed.

The pathogenic potentiality of fungi is related to numerical content and climate season while the production of toxins is intimately related to their growth on carbohydrate-rich substrates under adequate conditions of temperature and humidity.

The genera of fungi with the highest pathological incidence in poultry are: Fusarium, Penicillium, Mucor, Aspergillus, Alternaria, Cladosporium, several belonging to yeasts (Rodotorula, Candida, Geotrichum) and sterile mycelia. Its incidence on avian pathology is strongly seasonal. Furthermore, almost two hundred species producing toxins are known, of which have interest about twelve toxins grouped into five groups according to their structure and fungal origin.

1. Derived from coumarins rings produced by Aspergillus: aflatoxins B1, B2, G1, G2 and sterigmatocystin
2. Derivatives with lactonic rings produced by Penicilliumand Aspergillus: patulina and ochratoxins.
3. Derivatives with lactonic rings produced by Fusarium: zearalenone.
4. Sesquiterpenes derived of trichothecene produced by Fusarium: Nivalenol, deoxini-valenol, toxin T-2 and diacetoxiscirpenol.
5. Amino alcohols produced by Fusarium: fumonisins.

The consequences of the presence of fungi and mycotoxins in food can have a nutritional, health and industrial character.

From the nutritional quality point of view, the growth of fungi in raw materials and feed, produces the decrease in the metabolizable energy of grains between 5 and 25% and produces destruction of fats, proteins, carbohydrates and vitamins.

• Proteolytic reactions: They are small and the destruction of amino acidsis not measurable until very advanced states of deterioration. The most affected amino acids are lysine and arginine
• Lipolytic reactions.
• The destruction of carbohydrates with the release of carbon dioxide.
• Vitamins are used in the growth of the fungi themselves. Especially, vitamins A, D₃, E, K, B1, B2, B6, nicotinic acid, pantothenic acid and biotin

The health consequences are the production of mycosis and mycotoxicosis. These last, depending on their chemical structure, develop morbidity, erosions of the gastrointestinal mucosa, stunted growth, rejection of the food, immune system interference, hepatorenal syndrome, hemorrhagic syndrome, nervous syndrome and/or reproductive.

Industrial consequences affect management by the formation of cereal or feed clusters with the consequent loss of efficiency of machinery and the start of overheating processes:

In cereals or feeds contaminated by fungi, the temperature rise that can reach 50-55°C is initiated and increases the degree of humidity.

From this moment the yeasts can quickly raise the temperature to 65°C. At this temperature, fungi and thermophilic bacteria start their activity, taking it up to 75-80°C. If there is no intervention, the process, initially microbiological, initiates a chemical decomposition phase that can reach between 200 and 250°C.

Since each material has a critical ignition temperature, a slow or explosive spontaneous combustion may occur.

The most flammable products are those that have a high iodine index that indicates the degree of unsaturation: flaxseed, soy, cotton, peanut and rape.

V.4. Insects

Weevils (corn weevil or Sitophilus zeamais, wheat weevil or S. granarius and rice weevil or S. oryzae) and butterfly are frequent parasites of stored cereals and feed. Its presence destroys the cuticle and allows the dissemination of contaminating microorganisms and contact with starch-rich substrates. Rice and maize are the most frequently attacked.

V.5. Pollutant control measures

With the description of the five groups of pollutants (biochemicals, bacteria, fungal, insects and toxic seeds) and their dangers against nutritional quality, animal health or machinery efficiency, we have identified the essential objectives that should pursue processing methods in order to alleviate or eliminate their presence and consequences.

Given the current differentiation between ingredient-producing areas for broiler food and broiler-producing areas and their food, it is necessary to distinguish two groups of measures for the control of anti-nutritive factors: prior to the plant of food processing and the food plant’s own.

The pre-processing plant measures correspond to the seed and agricultural producer sector. They will not be described in this exhibition

The food plant’s own measures can be described in 4 sections:

• a) Feed formulation program

It should be considered the maximum limits in content of certain anti-nutritive factors and limit the use of those ingredients that provide them:

• b) On-site controls

Storage silos must meet the following characteristics: avoid wood and brick as building material, avoid hollowed walls, false ceilings, avoid square and angled shapes, be equipped with ventilation systems to be used in case of humidity greater than 12%, have installed temperature control systems (surface rings, floor plates and internal or different levels).

The rest of the installation (mills, scales, mixer, granulator) must be cleaned periodically.

• c) Raw material controls

Upon their reception, hygienic measures (separating dust from grain, separating broken grain from whole grain) should be taken and systematic analytical controls: humidity, dust and broken grain percentages, bacterial content, fungal and mycotoxins content, macroscopic (seeds) and microscopic analysis should be done to detect alterations.

• d) Use of technology and ingredients that improve quality:

Will relate between them:

• Mixing control techniques based in the use of micro tracers or chloride analysis.
• Use of granulation to fight alkaloids, trypsin inhibitors, bacteria and filamentous molds. Not effective against sporulated bacteria and toxins.
• Use of extrusion, which in addition to the effects of granulation, increases digestibility.
• Use of antioxidants, preservatives, mycotoxin absorbers, probiotics and enzymes.
• Use of specific nutrients:
• Iodine. It should be incorporated in greater percentage when diets are rich in cassava or hydrocyanic acid which decreases their absorption.
• Methionine. Its content will be increased in foods rich in tannin and hydrocyanic acid.
• Its content will be increased to reduce the effect of alkaloids.
• Choline. It should be increased in foods with synapia and tannins.
• Sulphur amino acids. Increase in foods rich in antitripsych factors.
• Lysine. It should be increased in foods rich in gossypol.
• D-mannose. Incorporated into the diet prevents the caecal colonization of tiphimurium. Its use is uneconomic.

VI. DEFICIENCY STATES, IMBALANCES, STRESS AND GRAZING

Deficiency states are exceptional situations in modern poultry or as a result of some food production error. The most likely deficiencies are vitaminosis A, E and riboflavin, which, by various mechanisms, attend with motor deficiencies: ataxia, encephalomalacia and muscular paralysis..

Biotin deficiency causes kidney and fatty liver syndrome, while manganese deficiency produces perosis.

The total or partial lack of water results in dehydration that leads to cannibalism.

Imbalance states are more frequent and are due to excesses of some component.

Thus, the excessive use of maize can cause cannibalism, excess calcium gout and if combined with lack of phosphorus urolithiasis. We have already mentioned that food should be formulated according to limiting criteria in the use of certain ingredients and the accumulation of antioxidants (pneumonia-ascites complex) should be avoided.

Stress can also be considered as imbalance. It originates from environmental factors (heat and cold), management (overconcentration) and infectious:

• a) Heat: It is the main stressagent in the broiler. Produces a decrease in foodconsumption that can be valued at 1.5% for each degree Celsius of increase. This decrease in consumption can lead to deficiencies in non-energy nutrients such as protein, minerals and vitamins.

The fight against heat should be based essentially on management measures (ventilation, water curtains) and construction adaptation (white refractory ceilings, cooling).

It is possible to incorporate drugs into the diet to combat the effects of heat: acetylsalicylic acid and sodium bicarbonate.

The use of acetylsalicylic acid in drinking water at doses of 10-15 mg/l decreases mortality in heat waves.

In contrast, the use of sodium bicarbonate should be done in usual hot periods. The incorporation of 17 kg of bicarbonate per Tm of food or 8.5 kg per thousand liters of water manages to increase the consumption of food (2300 to 2400 g in 20 days) and the weight of the broiler (1150 to 1220 g in 20 days) to 30°C temperature.

• b) Cold: It is a stressfactor that affects to a lesser degree the broilerfrom 15-20 days of age. Its main consequence is the increase in consumption that can be fought by increasing energy content.
• c) Concentration excess: It affects in a way that it decompensates the availability of water, foodand makes it difficult to exchange gases and heat with the outside. Its consequences will be those corresponding to each case, although in general increases the risk of cannibalism, the number of drowned broilers and the environmental microbial load.

It is advisable not to exceed 25 kg of meat per m² in summer and 27 kg in winter. There should be no attempt to breed more broilers on each shed than the average of those taken out in the previous breeding. In any case, the decrease in luminosity is a useful measure in circumstances of overconcentration.

• d) Clinical infectious states (CRD, salmonellosis, necrotic enteritis, coccidiosis) or subclinical (on vaccine load and reactions) are important stressfactors that should be minimized. The use of prophylactic drug programs and reducing vaccinations with live germs to the essential ones are advisable. In any case the use of vitaminC is beneficial.
• e) Grazing. It is an unusual breeding system in modern poultry farming. Although grass is very rich in vitamin A, B complex, calcium and protein; it presents the problem of lack of consumption and digestibility if not tender, due to the increase in fibrous content.

Therefore, if it is wanted to breed broilers in grazing it is necessary to program the rotation of grass plots, the planting of suitable planting species such as clover, alfalfa, legumes and rapeseed; as well as having enough space (1300 m² for 100 broilers).

All this save between 5 and 20% of the necessary food in conventional farm breeding.

Another variant is the confined breeding with the contribution of hay. This should be of good quality and keep the color green. In this breeding it is advisable to supply the hay at noon and remove it at night. It is necessary to provide about 3 kg daily for 100 broilers. This contribution also saves compound food.

VII. NUTRITION, HANDLING AND PATHOLOGY: PRODUCTIVE PERFORMANCES

It is traditionally said that an animal is like a three-legged table: growth, health and reproduction. If one of them is manipulated to increase its yield or rusticity, an imbalance unfavorable to the others occurs.

The broiler is a clear case. Its high efficiency in growth affects its rusticity. Therefore, the benefits of good nutrition will not be observed without adequate control of the management and microbiological factors that may be cause of disease.

Therefore, we recommend adopting an integral plan taking into account:

7.1. Use chicks from a supplier that produces in a properly way.

7.2. Check weight and immune status (mycoplasmas and salmonella) on arrival. Minimum weight 35 g. Acceptable average weight 38-40 g

7.3. Rehydrate the chick.

7.4. Adopt a table of requirements that takes into account for each age the needs of space, availability of feeders and drinkers, temperature, lighting and ventilation. Train the farmer in detail.

7.5. Periodically monitor the weight, losses and consumption of foodwith special incidence in the days of food change.

7.6. Adopt the formulation of food to the climatic season.

7.7. Adopt a health program based on analysis and preventive use of drugs.

Our line of work is based on the use of an antimicoplasmatic on days 1-2-3, 15-16-17 of life, on sampling (head and femur) on day 21 and preventive treatment on days 33-34-35, based on the analytical results of the samples on day 21.

Adopt an efficiency index that allows to evaluate, at the end of each breeding, the results of the work program. Our criteria is to adopt:

If the result is lower than 250, efficiency is bad.

If the result is between 250-310, efficiency is acceptable.

If the result is over 315, breeding is very efficient.

Parallel to this productive assessment, another economic one should be performed that takes into account the costs of the chick, food and medication with respect to the weight of the chick, the value of the meat produced and the efficiency index.

VIII. CONCLUSIONS

There is sufficient knowledge to produce quality chicken meat at an affordable price and safe for the population. The application of this scientific knowledge through technological programs constitutes an art with professional traits of each nutritionist.

Nutrition is the highest cost in poultry production.