SALUD DEL TGI FUNCION PRINCIPAL DEL TGI

� Desde el punto de vista de la Nutrición Animal Elaparato digestivo puede presentar múltiplesvariantes morfológicas; pero el proceso digestivotiene el mismo proposito en todos los animales:

CONVERTIR LOS GLÚCIDOS, LÍPIDOS Y PROTEÍNAS EN UNIDADES MAS SENCILLAS, POR MEDIO DE LOS

MECANISMOS Y FACTORES INVOLUCRADOS EN LA DIGESTIÓN y ASEGURAR UNA EFICIENTE ABSORCION

SALUD DEL TRACTO GASTRO INTESTINAL : TGI

- DIGESTION (accion mecanica por masticacion, accion quimica por HCl, enzimas).

- TRANSPORTE DE DIGESTA (contracciones peristalticas).

- ABSORCION (transporte activo, pasivo,) nutrientes a la sangre).

- SINTESIS (proteinas verdaderas, acidos grasos, carbohidratos, vitaminas).

- EXCRECION ( productos de desecho: por la bilis se excreta toxinas, microbios, etc y por el recto se excreta calcio, magnesio y fosforo)

IMPORTANCIA DE LA SALIVA

� FUNCIONES DE LA SALIVA :

- SOLUBILIZACION de alimento seco- LUBRICACIÓN Liga el alimento formando bolo alimenticio.

- ENZIMÁTICA (Amilasa).

- BUFFER (Bicarbonato de Sodio)- HIGIENE Oral- ENFRIAMIENTO EVAPORATIVO de algunas especies animales.

- CONTROL DE SECRECIÓN (volumen y tipo) dependiente de sistema nervioso central

SECRECION DE SALIVA & AGUA

� Cantidad y composición de la saliva varia considerablementeentre especíes.

� Cantidad relacionada al nivel� Cantidad relacionada al nivelde actividad de masticar

� Cantidad de secreción:

- PERROS minima (lubricacion, no enzimas).

- OVEJAS 3-10 litros/d

- CABALLO 10-12 litros/d

- VACUNO 130-180 litros/d

DIGESTION

• Carbohidratos→ monosacaridos

• Proteinas→ peptidos pequeños y aminoacidos

• Lipidos→monogliceridos y acidos grasos

� Digestión de los carbohidratos: Amilasa salival (boca) amilasapancreática (intestino delgado), disacaridasas(intestino delgado)

� Digestión de las grasas: Lipasa pancreática

� Requiere de la presencia de bilis.

� Digestión de Proteínas: Pepsina en el estómago. Endopeptidasas deorigen pancreático y Exopeptidasas (carboxipeptidasa de origenpancreático

DIGESTION EN VARIOS NIVELES

� DIGESTION INTESTINAL :

� Bilis hepática: sin fermentos emulsiona grasas rico en Na y K favorece el peristaltismointestinal, rebaja la tensión superficial del quimo, favorece la hidrólisis, impide la proliferaciónde bacterias de la putrefacción y otros mcorg. Perjudiciales.

� Jugo entérico: Amilasas, Proteasas y Lipasas

� Jugo pancreática: Tripsina: Proteínas y péptidos en AA

� Amilasa: Almidón e H.C. en azúcares

� Lipasa: descompone grasas en a. grasos y glicerina. Máxima actividad con pH 8

� DIGESTIÓN GÁSTRICA:

� Ac. Clorhídrico

� Pepsina: Proteínas = polipéptidos + péptidos + peptonas

� Cuajo o renina: en lactantes, coagulación para facilitar la digestión

� (nata, caseína y lactosa) y el suero: (lactosa, lactoalbúminas, NNP y sales minerales)

� Lipasa: Actividad limitada por el bajo pH: Ac. Grasos + Glicerina

proteína delalimento polipéptido

diipéptido

proteínaindigestible

DIGESTION DE PROTEINAS

aa disponibles

masticación HCl pepsina tripsina quimiotripsina carboxipeptid. minopeptid. elastasas

DESARROLLO DE ENZIMAS

LECHON

DESARROLLO DE ENZIMAS(unids/kg p.v. en intestino a los 10 días de edad)

POLLOSPOLLOS

ALIMENTO

RESIDUO NO DIGERIDO

INTESTINO DELGADO ABSORCIÓN

secreciones endógenas

Reingestión

DIGESTION EN CONEJOS

partículas gruesas

HECES DURAS

partículas finas

CIEGO

HECES BLANDAS

AGV

DIGESTION EN EQUINOS

DIGESTION EN RUMIANTES

� Producción diaria de saliva: VACUNO: 150 l.; OVINO: 10 l.

� CONTENIDO RUMINAL: en 3 Fases:

- Inferior: líquida y finas partículas

· Superior: más seca y partículas

FERMENTACIÓN DE ALIMENTO

Microorganismos anaerobios

Condiciones homeostáticas:� pH: 5,5-6,5 (fosfato y bicarbonato de la saliva y rápida absorción de · Superior: más seca y partículas

groseras

· Agua: 850-930 g./Kg. MS

� DIGESTIÓN QUÍMICA Y FÍSICA

· Masticación: 40-50 veces

· Tiempo de masticación: 8 h.

· Tiempo de rumia: 8 h.

la saliva y rápida absorción de ácidos).

� Presión osmótica: próxima a la sangre (iones)

� Anaerobiosis: consumo rápido de oxígeno

� Temperatura: 38-42 ºC

m.o.

PRINCIPALES MICROORGANISMOS ANAEROBIOS DEL RUMEN :

1. BACTERIAS

� 109-1010 por ml.

� Más de 60 especies

2. PROTOZOOS

� 106 por ml.

� Mayor tamaño

� Ciliados

- Grupos:� Más de 60 especies

� Número y proporción según dieta � ISOTRICHIDAE U HOLÓTRICOS

� · Isotricha y Dasytricha

� · Ovalados

� · No ingieren partículas ni celulosa

� OPHYOSCOLECIDAE U OLIGÓTRICOS

� · Entodinium, Diplodinium, Epidinium y Ophryuoscolex

� · Tamaño y forma variable

� · Ingieren partículas y celulosa

QUE HACEN LOS m.o.

� Funciones de los m.o. :

� -digiere la fibra a AGV

� -fabrica proteina

� -fabrica vitamins K and B complex

� La funcion del rumen es alojar microorganismos, similar en conejos y caballos cuy,

� Syntetiza todas las vitaminas del C. B, excepto vitamin B12, que requiere Co para su sintesis

� Syntetiza todas las vitaminas del C. B, excepto vitamin B12, que requiere Co para su sintesis

� Produce amonio: Utilizado por los m.o. para formar AA´s, pueden absorver AA´s para formar proteinas, pero parcialmente, satisfacen las necesidades de proteinas por digerir algunos m.o. Esto ocurre en el abomaso e intestino delgado

� Microorganismos en estomago convierte celulas vegetales en energia utilizable.

� Celulosa es degradado por accion microbiana.

� Los Acidos Grasos Volatiles de Cadena Corta (AGVCC) Aportan con el 60-80% de la energia dietaria de rumiantes (dependiendo de la dieta).

� Grandemente absorvidos desde el � Grandemente absorvidos desde el estomago en la circulacion portal hepatica.

� Pricipales SCFAs:

› Propionato: utilizado por el higado (gluconeogenesis)

› Acetato utilizado para energia y formar grasas

› Butirato utilizado para energia

RUMIACION

� Rumia � Comprende un ciclo de actividad de 4 fases : la regurgitación

de la ingesta seguida de una remasticación, reensalivación y nuevade la ingesta seguida de una remasticación, reensalivación y nueva

deglución.

� Esto logra disminuir el tamaño de partícula del alimento y aumentar la

superficie para la fermentación microbiana.

� Ocurre principalmente cuando el animal descansa y no come.

DIGESTION FERMENTATIVA (FERMENTACION)

• Todos los mamiferos tienen alguna capacidad fermentativa que les permite lautilizacion de la fibra ingerida.

• La importancia comparativa de la fermentacion esta relacionada a la fraccion dela digesta total contenido en los compartamentos fermentativos del TGI i

� Bacterias anaerobicas, protozoa y hongos producen enzymas quedegradan la cellulosa, hemicellulosa y pectinadegradan la cellulosa, hemicellulosa y pectina

� Productos de la digestion fermentativa :

› Acidos grasos de cadena corta (SCFAs), tambien llamados acidosgrasos volatiles (VFAs)

› Gas metano

› CO2

› Amoniaco (NH3)

FERMENTACION EN MONOGASTRICOS

� Limitada fermentación post gástrica (colon, recto y ciego)

Cantidad de tiempo que toma elmaterial para viajar de una partedel intestino a otra.

Cuando el material viaja a traves del

TIEMPO DE TRANSITO EN EL TGI

Cuando el material viaja a traves delintestino muy rapido, disminuyeel tiempo de transito intestinal.

Cuando el material viaja a traves delintestino lento, se incrementa eltiempo de transito intestinal.

ESTRUCTURA: BASE DE LA ABSORCION

The villi increase the surface area of the ileum for the absorption. The villi are finger like projections into the lumen of the gut. The villi increase the available surface area by ten times.

The crypts contain the secretory cells of intestinal secretion.cells of intestinal secretion.

Mucosa is a mucus secreting membrane.

The circular and longitudinal muscles combine to create the contractions known as peristalsis that maintains the movement of chyme along the alimentary canal.

The serosa is a tough outer membrane composed of collagen.

TRANSPORTE ACTIVO

Active Transport : Glucose absorption and Amino acids absorption into the epithelial cells. •Active mean that the membrane protein 'pump' requires energy to function •The source of energy is ATP from respiration

•This moves the molecules from low to high concentration against the concentration gradient

•The energy causes a shape change in the protein that allows it to move the molecule to the other side of the membrane.

PARTICULARIDADES DE LA ABSORCION

Many substances in the diet are composed of small molecules that need little or no digestion. These include sugars, mineral ions, vitamins and water. These are absorbed by different transport mechanisms:

•Cholesterol and the fat-soluble vitamins (A, D, E, K) are absorbed into the epithelial •Cholesterol and the fat-soluble vitamins (A, D, E, K) are absorbed into the epithelial cells of the ileum by lipid diffusion

•Mineral ions and water-soluble vitamins are absorbed by passive transport in the ileum •Dietary monosaccharides are absorbed by active transport in the ileum

•Water is absorbed by osmosis in the ileum and colon.

1. Monogastricos ó no-rumiantes

2. Rumiantes o:

- Pre-gastrico

CLASIFICACION DE LOS ANIMALES POR SU INGESTA DE ALIMENTOS PREFERIDO

- Pre-gastrico fermentacion (craneal)

- Post-gastrico fermentacion (caudal)

Clases Especies Habito dietario

Rumiantes Vacuno, oveja

Ciervo, antilope, camello

herbivoros q pastan

herbivoros selectivos, incluyendo folivores and frugivores

FERMENTADORES PREGASTRICO

frugivores

Norumiantes Mono colobine, hamster

Kangaroo, hippo

herbivores selectivos

Herbivores selectivos y quepastan

Clases Especies habito dietario

Digestores cecal CapybaraConejoRata, raton

Pastanherbivores selectivosOmnivoros

digestores

FERMENTADORES POSTGASTRICO

digestorescolonicosSacculados

Unsacculated

Elephant, caballo, zebraMonos del nuevo mundocerdo, humanoPanda

Perro, gato

PastanFolivorosOmnivorosHerbivorosCarnivoros

FERMENTACION COMPARATIVA POR ESPECIES

CAPACIDAD DIGESTIVA COMPARATIVA

SALUD DEL TGI

� Integridad anatómica y fisiológica (Estructura y Función).

� Microbiota del TGI: parte integral de la salud del TGI e influencia el desarrollo dela microanatomia, ayuda a los procesos digestivo, estimula el desarrollo del sistemainmune entérico y puede proteger contra la invasión de patógenos.

� Sistema inmune mucosal: la mucosa intestinal tiene una función de barrera, perotambién puede generar una respuesta inmune protectiva contra patógenos. El TGItambién puede generar una respuesta inmune protectiva contra patógenos. El TGIalberga el mas grande numero de células inmunes en el cuerpo.

Fotos de: Collet, S. University of Georgia - 2008

Tabla 2. Cantidad de bacterias (log CFU/g) en el tracto intestinal del pollo en diferentes edades.

CRECIMIENTO ALOMETRICO

Tabla 1: Ingredientes y problemas potenciales en dietas para pollos sobre la salud intestinal

INTEGRIDAD DEL INTESTINO

� El TGI constituye una extensa superficie en la que se produce un CONTACTO ÍNTIMO entreel organismo y las substancias de la dieta, microorganismos, parásitos y toxinas exógenas.

� El intestino permite el PASO DE SUSTANCIAS a la circulación sistémica, pero al mismo tiempoEXCLUYE COMPUESTOS PATÓGENOS (Gaskins, 1997).

� El TGI tiene múltiples MECANISMOS DE DEFENSA inespecíficos e inmunológicos.

� Los mecanismos no específicos incluyen producción de ácidos gástricos, peristaltismo, capa� Los mecanismos no específicos incluyen producción de ácidos gástricos, peristaltismo, capamucosa, estrecha unión entre las células epiteliales, proteo lisis, resistencia contra lacolonización por bacterias patógenas y el eje intestino hepático.

� La defensa inmunológica del intestino delgado incluye la PRODUCCIÓN DEINMUNOGLOBULINAS secretoras, células M y linfocitos (Madara et al. 1990; Walker yOwen, 1990; Deitch, 1993; Wang, 1995).

� Los INDICADORES comúnmente usados para evaluar la integridad intestinal son la longitudde las vellosidades, profundidad de las criptas y número de células caliciformes,permeabilidad transepitelial, actividad enzimática de la superficie ciliada, inflamación ycrecimiento del animal.

INTEGRIDAD INTESTINAL (I.I.)(Cervantes, Phibro Animal Health Corp. EUA, 2011)

� Desarrollo completo, macroscópico y microscópico, a la integridadininterrumpida y al funcionamiento normal del tubo intestinal.

� La I.I. optima es, desde el nacimiento hasta el final del ciclo productivo, esesencial para obtener el MÁXIMO POTENCIAL GENÉTICO de crecimientoy utilización eficiente de los nutrientes del alimento en base a un TGIsaludable, una altura máxima de la villi, maxima densidad de la villi ysaludable, una altura máxima de la villi, maxima densidad de la villi ymáxima área absortiva.

� Es necesario estimular un desarrollo temprano, integro y completo delaparato GTI, glándulas y órganos anexos para maximizar la digestión yabsorción de nutrientes.

� integridad del intestino manteniendo su ESTRUCTURA Y FUNCIÓN osimplemente un intacto y sano intestino (Dr. Harish V. Dharne, head ofAvitech’s).

Higher villi in the jejunum (p<0.01) were seen when Bacillus subtilis-based probiotics were used compared to diets without this additive

VD was higher when probiotics based on Bacillus subtilis were used together with prebiotics

based on MOS, compared to the use of probiotics based on Bacillus sp alone. It was also

higher in the birds fed the probiotics containing a bacterial pool compared to those

containing only one culture (probiotic 1). The results suggest that, in order to obtain higher

VD (consequently higher nutrient absorption area), it is necessary to use MOS-based

saccharides when probiotics based in only one bacterial culture are used. On the other

hand, they would be not necessary if the probiotics has many bacterial cultures, as

observed for probiotic 2.

IMPORTANCIA DE LA INTEGRIDAD INTESTINAL (I.I.)

FACTORES QUE AFECTAN LA I.I.

CAUSA MAS COMUNES DE LA MALA I.I.

AGENTES ETIOLOGICOS MAS COMUNES DE LA ENTERITIS

RECOMENDACIONES NUTRICIONALES

� Acceso rapido de agua y alimento de buena calidad, para favorecer el desarrollo y maduracion precoz del tubo intestinal .

� Verificacion diaria del consumo (agua y alimento) mediante la palpacion del buche.

� Uso de enzimas para mejorar digestibilidad y reducir la viscocidad de cereales con contenido alto de polisacaridos no almidonados. con contenido alto de polisacaridos no almidonados.

� Verificacion y rechazo de materias primas para la fabricacion de alimentos contaminados con micotoxinas o aminas biogenicas.

� Evitar el uso de grasas rancias o no estabilizadas con antioxidantes o que no cumplan con los requisitos de calidad.

� Evitar el uso de soya mal procesada con contenido alto de inhibidores de tripsina.

�

Maintaining Gut IntegrityBy Dr. Harish V. Dharne, head of Avitech’s Business Promotion and

Knowledge Resource Centre

Nutrition and gut health are closely related in commercial poultry production.

� Diet formulation and feed management can have a marked effect on guthealth greatly influencing nutrient utilization and growth of the animal. Guthealth problems arise due to improper nutrition and an unhygienicenvironment especially during the early stages of chick development.environment especially during the early stages of chick development.

� For cost effective and sustainable commercial operations there is need to:

1. Maintain natural gut health through proper nutrition and a cleanenvironment, and

2. Effective treatment of an existing gut disorder.

TGI: FUNCION Y ESTRUCTURA

� To improve gut health, a clear understanding of the STRUCTURE AND FUNCTIONALITY OF THE GUT is important..

� Birds also have high numbers of intestinal villi and high EPITHELIAL TURNOVER RATE (48 TO 96 H), and rapid inflammatory response (less than 12 hours, as compared to 3-4 days in mammals), which makes them more susceptible to disturbances in absorptive capacity than mammals.

Transit time and pH in poultry GIT

GIT Segment Transit Time(Min) pH

Crop 50 5.5

Proventriculus / gizzard 90 2.5-3.5

Duodenum 5-8 5-6

Jejunum 20-30 6.5-7.0

Ileum 50-70 7.0-7.5

Colon 25 8.0

Source: R.Gauthier(2002)

Natural Physical Barriers that Help to Maintain Intestinal Integrity

� Physical barriers protect against the entry of foreign materials and organisms into thebloodstream and access to other viscera thus helping intestinal integrity. On occasion due toimproper nutrition or an unhygienic environment, when the load of foreign invaders increasethese barriers are breached.

1. Mucus (a protective1. Mucus: material secreted by intestinal cells) is a barrier to bacterial andfungal invasion. It is broken by some enzymes (eg. mucinolytic, urease). Poultry feeds withunder cooked soy meal may contain urease.under cooked soy meal may contain urease.

2. Gut epithelial cells (enterocytes): These cells form a semi-permeable surface that selectivelyallows passage of fluid, electrolytes, and dissolved nutrients. Every epithelial cell in thedigestive tract is part of a continuous physical barrier. When organisms and toxic agentsdamage epithelial cells, the integrity of this protective barrier is broken.

3. Fluid secretion: fluid having large amounts of water mixed with electrolytes. The fluid in theupper small intestine is protective and keeps bacteria in suspension and washes themdownstream.

4. Vascular supply: supply under the gut epithelial layer serves to rapidly dilute and carry awayany agents or chemicals (endogenous or exogenous) that may breach the mucosal barrier.

Factors Influencing Gut Integrity

a. Physical barriers: Intestinal integrity is compromised when the mucus layer isdegraded; epithelial cells are effaced or destroyed, the vascular supply isinterrupted, or the immune system is compromised. Viruses, bacteria, fungi,parasites, and toxins can damage this.

b. Stress factors: Gut environment is also altered by several stress factors to the birdslike handling, transportation, overcrowding, abrupt changes in environment etc.

c. Feed toxins and toxicants: Feed toxins and toxicants can also affect the gutintegrity.

d. Dietary factors: Nutritional deficiency due to imbalance in ration formulation, grainengorgement, microbial load in feed etc. affect gut health. The nature of the diet,for example presence of non-starch polysaccharide (NSP) especially solublefractions in the diet provide substrate for the growth of undesirable bacteria andaccumulation of fermentation products affecting the gut severely. Insoluble NSP is amajor problem leading to soiling of litter.

e. Health status: Diseases like coccidiosis and fowl plague are found to affect the gutintegrity severely. Infections, injuries etc. also affect gut health.

f. Gut micro flora: The rich bacterial community that make up the gut micro flora playan important role for the host through changes in the morphology of gut, nutrition,pathogenesis of enteric diseases, immune response and alterations in colonizationresistance. The shift in composition of this microflora results in production andefficiency losses often in the absence of any clinical signs. Useful microbesefficiency losses often in the absence of any clinical signs. Useful microbes(commensal bacteria) in gut play a positive role in controlling the gut flora andstimulate the development of the gut wall. Hence, microbial balance of gut is utmostimportant in maintaining gut integrity.

g. Beak deformity: Beak deformity preventing proper feed consumption may impairgut health.

Early Chick Nutrition and Gut Health

� Good start is an important factor in MAXIMIZING PROFITS from broiler operations.

� Early nutrition mainly in the first 7 days of life for broilers may program the birds' systems and set a patternfor growth and productivity. A large percentage of early growth (2 to 5 times the growth rate of othertissues) occurs in the digestive tract and those organs involved in digestion.

� If digestive growth is retarded during this time period, overall growth rate may be compromised. Furthernewly hatched chicks are more prone to gut infections as its natural defense is yet to be strengthened. Soproper care should be taken during this time period.

Feeding of chicks:� Feeding of chicks:

� Access to nutrients post hatch has a major impact on the immediate and long-term development of the chick.

� The immediate post hatch period is critical for the development of all systems in chicks including the immune system.

� The development of bursa and spleen is responsive to environmental stress at an early age in chicks.Delayed access to nutrients post hatch reduces the relative weight of bursa and spleen.

� The passage of feed that is not sterile, through TGI exposes the bursa to a variety of antigens. So the earlierthe chicks are fed post hatch, the sooner will the proliferation stem cell meet environmental antigens. Thisclearly suggests that early nutrition is important in laying a strong foundation for the health status of birds ina situation where little or no antibiotics are allowed in their feed. Suitable feed additives should be addedin the starter diet as precautionary measure that will ensure better health and productivity.

Role of Dietary Factors in Improving Intestinal Integrity

� Quality feed ingredients: Supplementation of quality feed ingredients helps inmaintaining natural gut health.

� Processed feed: Many incriminating factors of feed are destroyed due toprocessing. Extrusion is effective in reducing microbial contamination in feedstuffsand in Salmonella control.

� Pelleted feed: Pelleting provides scope for utilization of high fibre feed resources.� Pelleted feed: Pelleting provides scope for utilization of high fibre feed resources.Use of steam- pelleted feed seems to be of value in maintaining gut health.

� Feed additives: Commercial poultry production during the last 50 years hasbenefited from pharmaceutical and biological products that enabled flock size toincrease, genetic potential and improved nutritional formulations to be realized, andoverall production to increase. Food animal agriculture is providing wholesomepoultry meat protein for consumption in the human diet at unprecedented levels.Some feed additives that promote the gut health either directly or by preventingthe enteric pathogens are discussed below

ADITIVOS QUE PROMUEVEN SALUD DEL TGI

� ANTICOCCIDIALS AND IONOPHORES; coccidiosis, a managemental disease, causes devastating losses tothe poultry industry. The disease is characterised by an invasion and damage of the intestinal wall by theparasite resulting in severe haemorrhage and mortality. For this reason, it is essentially added in mostpoultry rearing situations during the rearing period to prevent illness and control infections. When used in astructured and monitored programme, anticoccidial agents are very effective and permit the optimumperformance of the animal without compromising health status. No new anticoccidial agent has come ontothe market since the 1980s, which is in part a reflection of the success that the ionophores have brought tothe control of the disease.

� PROBIOTICS (DIRECT-FED MICROBIALS); “A probiotic is defined as a live microbial feed supplement whichbeneficially affects the host animal by improving its INTESTINAL MICROBIAL BALANCE.”

Gut flora may be disturbed under several circumstances including the use of antibiotics or other drugs,excess stress, disease, exposure to toxic substances, which allows harmful competitors to thrive in the gut.Probiotics prevent such harmful bacteria (enteric pathogens) from growing in the gut and thus minimize thedisturbances caused by them, and also maintain host favourable bacteria. Thus Probiotics balance gutmicroflora.

Probiotics are also used as an alternative to antibiotics. However, probiotics are not a substitute forantibiotics in birds with serious infections but are useful in restoring the normal bacterial population that wasotherwise altered due to administration of antibiotics. If the conditions that originally caused damage to thenatural gut flora persist, the benefits obtained from probiotic supplements will be short lived.

� PREBIOTICS; are non-digestible food ingredients (readily fermentablesugars), that beneficially affect the host by selectively stimulating thegrowth and/or activity of one or a limited number of bacteria in the colon,and thus improve host health. Most potential prebiotics are carbohydrates(such as oligosaccharides). Prebiotic oligosaccharides may be added toprocessed foods. Some prebiotics that are used in this manner againstpathogens are fructo-oligo-saccharides (FOS), xylo-oligo-saccharides(XOS), mannan-oligo-saccharides (MOS) and galacto-oligo- saccharides(GOS).

� SYNBIOTICS; although use of probiotic formulations may well help in� SYNBIOTICS; although use of probiotic formulations may well help inachieving these benefits, it is also possible to increase and maintain ahealthy bacterial gut flora by increasing the amounts of prebiotics in thediet such as inulin (naturally occurring oligosaccharides), raw oats, andunrefined wheat. As probiotics are mainly active in the small intestineand prebiotics are only effective in the large intestine, the combination ofthe two gives a synergistic effect. Appropriate combinations of pre- andprobiotics are termed as synbiotics.

� ACIDIFIERS/ORGANIC ACIDS; include short chain fatty acids, volatile fatty acids andweak carboxylic acids that are only partly disassociated. They may play a role inmaintaining gut integrity in the way that they reduce the colonization of pathogens (likeSalmonella and E.coli) in intestinal wall by lowering the intestinal pH below 6.0, andpromoting the normal microflora growth. This condition also increases the efficiency ofall digestive enzymes. Daily application of short chain fatty acids such as Butyric acidsincreases epithelial cell proliferation, quick repairing of the intestine, increased villousheight and in turn increased absorptive capacity. Alone or in combination, these arebeneficial to the animal's health.

� ENZYMES; extra enzymes can add to the animals' own digestive capacity. Feedinghigh viscosity cereal grains to broilers result in larger microbial populations in the ileum.Viscosity reduces the passage rate of the feed leading to overall reductions inViscosity reduces the passage rate of the feed leading to overall reductions inconsumption and decreased performance, sticky droppings and dirty eggs. A viscousenvironment slows down digestion processes, and encapsulates nutrients, making theminaccessible to digestive enzymes. Viscous gels are formed in the digesta by thesoluble NSP, which are not digested by the animal's own enzymes. Thickening ofunstirred water layer due to gel formation also inhibit absorption. Thus non-starchpolysaccharides form a major target substrate for feed enzymes. The addition ofenzymes to address NSP viscosity can improve gut health, feed efficiency, improvemanure quality and facilitate the use of lower cost feed ingredients.

� TOXIN BINDERS; are used through feed to bind or adsorb deleterioussubstances such as mold and fungi-borne mycotoxins. These are the invisiblethieves or a hidden danger in animal feed, to animal health and production.They may also accumulate in animal products and contaminate the humanfood chain.

� ANTIBIOTIC GROWTH PROMOTERS; With the intensification of livestockfarming the use of antibiotics for growth promotion has become popular.Antibiotic growth promoters are feed additives that are administered at alow, sub therapeutic dose to suppress sensitive populations of bacteria in thegut and improve growth and performance of bird. The reason is that agut and improve growth and performance of bird. The reason is that areduction in gastrointestinal infections would result in the subsequent increasein muscle weight. It has been estimated that as much as 6 per cent of the netenergy in the diet could be lost due to microbial fermentation in the intestine(Jensen, 1998) and stimulation of energy-consuming immune responses. If themicrobial population could be better controlled, it is possible that the lostenergy could be diverted to growth. Whatever the mechanism of action, theresult of the use of growth promoters is an improvement in daily growth ratesbetween 1 and 10 per cent resulting in meat of a better quality, with less fatand increased protein content

Limitaciones del uso de los antibioticos:

� An overuse of any antibiotic over a period of time may lead to the localbacterial populations becoming RESISTANT TO THE ANTIBIOTIC.

� ANTIBIOTIC RESIDUES in the products may affect humans.

� Essentially, there are two main ways in which we can reduce ourdependence on antibiotic use in animals:

1. An obvious choice is the development of ALTERNATIVES TO ANTIBIOTICSthat work via similar mechanisms, promoting growth whilst enhancing theefficiency of feed conversion.

2. A more difficult route would be to IMPROVE ANIMAL HEALTH.