Parker coined the term ‘probiotic’ in 1974 and defined itas “organisms and substances which contribute tointestinal microbial balance”.Probiotics are live cultures of non-pathogenic organismswhich are administered orally.Later Fuller in 1989 redefined them as live microbialfeed supplements which beneficially affect the hostanimal by improving its intestinal microbial balance.They may include microbial cells, microbial cultures andmicrobial metabolites.Most probiotics get destroyed by upto 80% in thepresence of antibiotics or when mixed withantimycoplasma drugs in the feed.INTRODUCTION :
The US food and drug administration (USFDA) used theterm direct fed microbes(DFM) instead of probiotics.Available forms :Probiotic products are available in the form of oralpastes, water dispensible powders or liquids or directlyfed feed additives.Some companies developed thermo-positive process toformulate microbial cultures and microbial viabilityisassured in the pelleted feeds.Eg: primalac DFMSome developed viable bacterial spores of selectedbacillus strain which are heat resistant.The recovery rate of organisms after pelleting is 95 %.
The DFM, includes : various bacterial cultures and yeastcultures.Various bacterial cultures includes :Lactobacillus spp :L.acidophilus, L.casei, L.delbreukiisubsp.bulgaricus, L.brevis, L.cellobiosus, L.curvatus, L.fermentum, L.lactis, L.plantarum, L.reuteriiStreptococcus spp :S.cremoris, S.faecium, S.diacetylactis, S.intermediusthermophilus, S.lactisBifidobacterium spp :B.bifidum, B.adolescentis, B.animalis, B.infantis, B.longum, B.thermophilum
Aspergillus spp :A.oryzaeVarious yeast or fungal cultures includes :Saccharomyces spp :S.cerevisiae, S.boulardiiFormerly yeast is known to contain compounds formerlyreferred to as UGFs (unidentified growth factors).Hungate (1966) observed that rumen bacterialconcentrations increased when fermentation productssuch as yeast cultures were added to the diet.He concluded that the stimulatory effects was due tometabolites in the fermentation products which served asnutrients for the bacteria.
Byproducts of fermentation includes : Dried brewersyeast , dried distillers solubles, dried bacterial press cakes.An increase of 1.1 kg milk yield/day with inclusion of 50gms of an active yeast/day was noticed.: Effect of yeast :On animal physiology :Reduces the temperature in heat stressed animals.Not shows effect regarding physiology in cool weather.The mechanism of action exerted by fungal cultures onbody templ and resp. rate is unclear.
Yeast cultureIncreased bacterial populationIncreased flow ofmicrobial proteinIncreased degradation offibre in rumen leading toincreased feed intakeIncreased animal productivityAction of yeast culture in Ruminants
Characteristics of a good probiotic :The culture should exert a positive effect on the host. Itshould be gram positive, acid resistant, bile resistant andcontain a minimum 30×109 CFU per gram.The culture should possess high survival rate andmultiply faster in the digestive tract. It should be strainspecific.The culture microorganisms should neither bepathogenic nor toxic to the host.The adhesive capability of microorganisms must be firmand faster.Should be durable enough to withstand the duress ofcommercial manufacturing, processing and distribution sothat the product can be delivered alive to the intestine.
: Mode of action of probiotics :Competitive exclusion :Oral administration of a suspension of caecal contentsor faeces obtained from adult chickens to newly-hatchedchicks increase their resistance to oral infection bysalmonella and this phenomena is called competitiveexclusion(Nurmi and Rantala,1973).A direct competition between native gut flora andSalmonella for attachment to a local site in gut epitheliumis noted.In the healthy animal Lactobacilli colonize quickly in thegut to displace the coliforms and reaching population of107 to 109 by one week of age (Karney et al).
Acid production and lowering of PH :The lactic acid bacteria produce organic acids like aceticand lactic acids in large quantities, which reduce intestinalPH(Fox 1988).The organic acids are toxic for the undesirablemicroflora in the intestine and this toxicity is increasedmanifold at low PH , as the undissociated form of theseorganic acids has better penetration into the bacterialcells and disrupting the bacterial cell.The antagonistic effect of Lactobacillus againstEnterobacterium and Salmonella is due to lactic acidproduction.
The antagonistic activity of lactic acid bacteria towardspathogens can be attributed to the production ofbactericidal substances like :-Acidophilin, Acidolin, lactobacillin, lactocidin e.t.c…..These antibacterial compounds have been foundeffective againstSalmonellae,Shigellae, proteus, Klebsiella, E.coli, Pseudomonas, e.t.c….Hydrogen peroxide produced by some Lactobacillus spp.Appears to be partially responsible for the antagonisticinteraction since it has strong germicidal activity at low PHenvironment (Gilliland, 1990).Excretion of antibiotic like substances :
Deconjugation of bile salts :Most of the lactic acid producing bacteria has the abilityto deconjugate bile acids to free from i.e. cholic acid,deoxycholic acid and taurocholic acid.This deconjugation of bile acids by the probiotic cultureenhances its anti-microbial nature and the production ofanti-microbial compounds (Acidolin and Reuterin), whichfurther reduce the population of harmful bacteria in thegut(Juven et al,. 1991).
acidsacidsacidsproduction of anti-microbialcompounds
Microbial enzymes are beneficial to the host becausethey increase the digestion of nutrients especially in thelower intestine (Sissons, 1989).Lactobacillus spp., which was used in cheeseproducts, was found to have lipolytic, amylolytic andproteolytic activities (Lee and Lee, 1990).Digestive enzyme activity :Antimutagenic and anticarcinogenic activity :Microbial feed additives suppress the activity ofmutagenic compunds.The activities of carcinogenic enzymes such asnitroreductase, azoreductase and β-glucuronidase in theguts of rats can be reduced by supplementation ofLactobacillus acidophilus (Goldin and Gorbach, 1977).
Ammonia production :Yeo and kim (1977) reported that feeding of probiotic(L.casei) significnatly decreased the urease activity in thesmall intestinal contents of broiler chicks during the first 3weeks.This suppression of ammonia production and ureaseactivity by probiotic culture may be beneficial forimproving animal health and enhancing growth becauseammonia produced by ureolysis in the intestinal mucosacan significantly damage the surface cells.Also beneficial for minimizing respiratory problems andreduces environmental pollution from poultry farming.
Anticholesterolemic effects :Feeding of Lactobacillus decrease the level of cholesterolin serum.The anti-cholsteromic activity of lactic acid bacteria isexpressed by 3 ways :By inhibiting cholesterol synthesisBy inhibiting intestinal absorption andBy deconjugation fo bile salts (DeRodas et al,.1996).
Immunomodulation :DFM activate immune system by increasing thephagocytic activity of lymphocytes, production of T-helpercell mediated cytokines by spleen cells and inhibition of IgEand IgA production and by protecting the Gut associatedlymphoid tissue (GALT) to come in contact with differentantigens (Saloff coste 1995).
Enhancing feed intake and digestion :The microbes take part in the metabolism of dietarynutrients such as carbohydrates, protein, lipids andminerals and also in the synthesis of vitamins.Nahason et al,.(1992) reported that supplementation oflactobacillus culures in maize-soyabean diets increased theretention of nitrogen, phosphorous, copper andmanganese in layers.
Advantages of supplementation of DFMin various sps :DFM for calves :During the first 2 weeks of the calf’s life, it is especiallyeasy for toxin-producing coliform bacteria like E.coli tocolonise the gut.This irritates the intestinal tract, resulting in a ‘hyper-secretion’ of fluids that leads to scours.Certain types of DFM oral pastes and feed supplementsare designed to prevent or reduce E.coli scours in calves.Stress such as extreme weather or transportation, wouldmore likely enhance the potential benefit of feeding a DFMto calves.
DFM for pigs :Probiotics have shown the greatest potential in veryyoung and growing pigs.Feeding probiotics improved weight gain and feedefficiency.Sows consuming diets supplemented with probioticbacteria weaned larger, heavier litters.Litter size at weaning 9.7 9.0*Pre-weaning mortality (%) 7.0 12.1*Piglet diarrhoea score 0.08 0.24*Piglet weight at weaning (kg) 8.40 8.02*Total creep feed intake per litter 6.4 5.9*Probiotic group Control groupProbiotic effect on pre-weaning piglet performance
DFM for poultry :The role of the intestinal microflora in health anddigestion of poultry is more extensively understood than inmammalian species.A low PH favours Lactobacillus sp. And a high PH isoptimal for E.coli.It was reported that Lactobacilli can be found in cropepithelial tissue as early as day one of life. These microbesattach to the crop epithelium and colonize the surface.Supplementation of a lactobacillus product in the wateror feed along with an acidifying agent would be effective incontrolling the coliform proliferation.Lactobacillus stimulates the weight gain and feedefficiency of broilers.
DFM for ruminants:Feeding probiotics leads to increased fibre digestibilityand hence production of animals.Significant improvement in feed intake, feed conversionefficiency and growth performance is noticed incattle, sheep and goat.Also inhibited methane production. The probable ways ofinhibition of methane production are :1) By increasing butyrate or propionate2) By reducing protozoa numbers thus affectingadversely the methanogens associated with theprotozoa.3)By stimulating the growth of acetogens which utilizehydrogen thus channalizing hydrogen towards acetateproduction.
Considerations in use of proibiotics :The response to probiotic feeding depends on a numberof factors such as composition of the product, viability andstability of the culture, dosage rates, duration of feeding,method of administration, ages of the animal used in theresearch studies, effects of environmental and nutritionalfactors on probiotic viability in the intestines and form ofthe culture.The positive influence shown with a particular probioticmay not always be repeatable in other similar experimentsand the influence will be more pronounced in stressfulconditions.It is highly advisable to adhere to storagerecommendations (i.e., away from moisture, excess heatand light) for maintenance of stability of the probiotic.
Examples of commercial preparations :YEA-SACC 1026 , VETCARE - DOSE 1 KG/tonn of broiler feed.400-600 gm/tonn of layer feed.Lacto-sacc (MicroencapsulatedLactobacillus, Streptococcus, enzymes and yea-sacc1026), vetcare/Alltech,Inc.Nutri-sac for dairy cows (contains bypassprotein, niacin, selenium and yea-sacc1026 )Dose : calves 100 gms/head/day, cows 200 gm/head/day.
: PREBIOTICS :Introduction :A prebiotic is a non-digestible food ingredient thatbeneficially affects the host by selectively stimulating thegrowth or activity of one or a limited number of bacteriain the colon and thus improves the host health (Gibsonand Roberfroid, 1995).Efficient prebiotic need to induce a specificfermentation in the colon.Characteristics of a good prebiotic :Should be neither hydrolyzed nor absorbed in the upperpart of the GIT.Should be a selective substrate for one or limitednumber of bacteria commensal to caecum/colon, which
Are stimulated to grow or metabolically activated.Able to alter the colonic flora in favour of a healthiercomposition.Induce systemic effects that are beneficial to the host’shealth.Should have known structure, which can bedocumented. should be palatable as food ingredient and large-scaleprocessing must be easy.Types of prebiotics :Glucooligosaccharides(GOS), fructooligosaccharides(FOS),mannanooligosaccharides(MOS), trans-galactooligosaccharides(TOS), isomaltooligosaccharides, lactosucrose, polydextrose, soybean oligosaccharides(SOS),
and xylooligosaccharidesOthers are :-germinated barley foodstuffs, oligodextrans, gluconic acid, gentiooligosaccharides,pectic oligosaccharides, mannan oligosaccharides,lactose, glutamine,hemicellulose-rich substrate,resistant starch and its derivatives,oligosaccharides from melibiose,lactoferrin-derived peptide, andN-acetylchitooligosaccharides.
Lactose :Is a disaccharide consists of glucose and galactose.Due to the absence of lactase enzyme in chickenintestine, the ingested lactose asses intact through andenters to the lower segment of the intestine and caeca.The hydrolyzation of lactose that occurs is primarily dueto microbial utilization of the disaccharide.Fructooligosaccharides (FOS) :They can be found naturally in some cereal crops andonions.FOS consists of several β(1-2) or β(1-6) linked fructoseunits which may be linked to glucose residues.They stimulate the growth of bifido bacteria and toinhibit growth and multiplication of potentially pathogenicbacteria such as enterobacteria, clostridia and salmonella.
Fermentation of FOS leads to the production of shortchain fattyacid, which is substrate for energy metabolismin the colonic mucosa stimulating epithelial cell growth.Relationship b/w bifidobacteria and short chainfructooligosaccharides
mannanoligosaccharides (MOS) :MOS is obtained from the cell wall of yeast(saccharomyces cerevisiae).Mannose, the main component of MOS, is a uniquesugar because many enteric bacteria have receptors thatbind to it and carried out of the gut.The pathogenic bacterial cells have surface compoundscalled lectins which recognize these carbohydrates and bywhich they attach to the gut cells.The pathogenic bacteria binding to the enterocytes isdisrupted and instead they bind to the oligosaccharide andare carried out of the gut with the passage of the digesta.
Partially hydrolysed guar gum (PHGG) :It is the one of the most commonly used polysaccharideprebiotic for chickens.Obtained from the bean of cyamposis tetragonoloba.By selectively cleaving the mannan backbone chain ofguar gum using endo- β – D-mannnase, a mixture ofgalactomannans is obtained, which is known as PHGG.Inulin :Inulin, a linear β - fructan, is present in a variety of plantsincluding chicory root and wheat.It exhibits prebiotic properties and has been shown toenhance mineral absorption and increase beneficialbacteria in the colon.The Lactobacillus and Bifidobacterium populations weresignificantly increased in the inulin supplementation.
: Mechanism of action of prebiotic :Dietary oligosaccharides may directly inhibit the growth ofcertain intestinal pathogens by increasing the concentrationof lactic acid and there by decreasing ph in the lower gut(Choi et al,. 1994, okumara et al,.1994).By lowering the gut ph through lactic acidproduction:By inhibiting/preventing colonization ofpathogens :Microbes are able to attach to the mucosa throughfimbriae and competitively decreases the pathogenicbacteria.
Modifying metabolic activity of normal intestinalflora :saccharides indigestible by the host are fermented by theflora into volatile fattyacids (actate, propionate andbutyrate), lactate and several gases including CO2, methaneand hydrogen (Cummings, 1981).short chain fattyacids released from the fermentation aremetabolically utilized by the epithelial tissue of the intestineand also play a role in modulating endogenous metabolism(Demigne et al., 1986).
Stimulation of immune system :May stimulate the blood immune system after crossingthe intestinal mucosal barrier.Some pathogenic bacteria causes disease aftertranslocation through the intestinal wall and it is mostcommon in animals fed with fibre free diet.The oligosaccharides acts as soluble fibre and reducetranslocation and help to preserve systemic immunity(Monsan and Paul, 1995).
: PRACTICAL APPLICATION :Growth and nutrient utilization :The diets containing 0.4% FOS resulted in significantimprovement in average daily gain and feed efficiency (Xu etal.(2003).MOS derived from palm kernels increased the muscleweight gain in chickens when included at 0.3% diet (Puszatiet al., 1995).MOS also reduced the mortality of chicken and improvedthe performance . (Mc donald 2005).The ileal digestibilities of DM, Ca, P and CP was increasedsignificantly.Compunds such as FOS can be fermented by thefavourable bacteria, giving them a competitive advantage.
final Body wt. in chicks with and without prebioticssupplementation
Dietary supplementation of MOS reduces the excretion ofnitrogen and phosphorous and thereby minimizes the majorsources of environmental pollution.Poultry health :The use of prebiotics in the diets has been assumed tominimize the use of antibiotics and thus possible occurrenceof drug resistance in bacteria.FOS is effective against Salmonella (Fukata et al,. 1999)and Campylobacter (Schoeni and Wong, 1994).Dietary MOS had reduced caecal S.typhimuriumconcentrations (Spring et al,. 2000).Supplementation of PHGG in young hens, resulted in nosalmonella enteriditis.
: CONSIDERATION :Depends up on The criteria for including these studies inthe analysis were that the available report should haveincluded at least1) the daily dose of the prebiotic, 2) the nature of the prebiotic, i.e., inulin or oligofructose,3) the number of volunteers, and4) the number of bifidobacteria per gram of feces both atthe beginning and at the end of the supplementationperiod.