2.1       Introduction
            In a natural environment the establishment of a microbial population in the digestive tract of all warm blooded animals, soon after birth, is inevitable (Jernigan and Miles, 2012).
            Efforts to improve livestock productivity by manipulating digestion and the gut ecosystem have occupied scientist and farmers since the beginning of settled agriculture, and especially, the introduction of commercial livestock production, (Uguru 2004).
The ban on the use of antibiotics as growth promoters in the poultry industry necessitated the introduction of probiotics as natural alternative. However, according to (Kannan et al, 2005) it has some constraints like lack of viability, stability and inability to be established in the intestinal eco-system due to barriers like gastric acid, and bile acid, during its transit, etc. Alternatively, prebiotics have been suggested to achieve all the probiotic benefits while overcoming all its constraints Kannan et al (2005).
             Prebiotics have been defined according to Kannan et al (2005) as non digestible feed ingredients, which are grown substrates, specifically directed towards potentially beneficial bacteria already existing in the caecum and colon. Xu et al, (2003), Spring et al, (2000) and Pelicano et al, (2004) reported that the addition of prebiotics to the diet of broilers, layers and pigs led to improved performance by improving gut microflora.

2.2       Origin, Distribution and Morphology of Papaya leaf.
            The papaya tree  belongs to a small family- Caricaceae consisting of four genera. The genus Carica Linn is represented by four species in India, of which Carica papaya Linn is the most widely cultivated and best known species. Among other species are, C. cauliflora, C. pubescens Lenns and K. Knocb, C. quercifolia  Krishna et al, (2008).
            Papaya  probably originated in Southern Mexico and Costa Rica. Subsequently it was introduced as a plantation crop in Australia, Hawaii, Phillipines, Sri Lanka, South Africa, India, and in all tropical and subtropical regions Krishna et al (2008). It is grown both commercially and in in home gardens. Papaya is a polygamous species and it is difficult to identify  whether a plant   is male, female or hermaphrodite. It is a tree reaching 3-10m in height.  The flowers are, trimorphous and have frangrance  usually unisexual-dioecious,  densely pubescent cymes at the tips of the pendulous, fistular rachis, female flowers large, solitary or in few flowered racemes with a short thick rachis (Krishna et al, 2008). It also has large berry, varying in size, elongate to globose with a large central cavity, seeds black,  and enclosed in a transparent aril. The tree starts to bear fruits in 18 months of age or less. The leaves and unripe fruit contain milky juice in which the protein present is fermented papain , (Krishna et al, 2008).

2.3 Nutritional Value of Papaya
            Papaya is a common man’s fruit, which is reasonably priced and has a high nutritive value. It is low in calories and rich in natural vitamins and minerals (Krishna et al, 2008). Papaya is placed first among the fruits for vitamin C, vitamin A, riboflavin, folate, calcium, thiamine, iron, niacin, potassium and fibre (Krishna et al, 2008). The comparatively low calories content (32 kcal/100g of ripe fruit) makes this a favourite fruit of obese people who are running a weight loss programme (Onyimonyi and Onu, 2009). Papaya has more carotene compared to other fruits such as apples, guavas, sitaphal and plaintains, which are anti-oxidants that help to prevent damage by free radicals. Unripe green papaya is used as vegetable, it does not contain carotene but all other nutrients are present (Krishna et al, 2008). The fruit is a rich source for different types of enzymes. Papain, vegetable pepsin, present in good amounts in unripe fruit is an excellent aid to digestion, which helps to digest the protein in food at acid, alkaline or neutral media (Krishna et al, 2008). Thus, it can be prescribed for dyspeptic patients, as papain may help in the digestion of proteins. Papaya has the property of tenderizing meat. This knowledge is being put to use in cooking meat with raw pawpaw to make it tender and more digestible, (Onyimonyi and Onu, 2009).
            The fermented papaya fruit is a promising nutraceutical as an antioxidant. It improves the antioxidant defense in elderly patients even without any overt antioxidant deficiency state at the dose of 9 g/day orally, (Krishna et al, 2008). The papaya lipase, an enzyme tightly bonded to the water insoluble fraction of crude papin, is considered as a “naturally immobilized biocatalyst”.
            The dried fruit skin is a potential source as dietary ingredient for broiler chickens. It gives similar food consumption, food conversion efficiency, survivability and meat yields to a control diet when used up to 120 g/kg of diet, (Fouzder  et al, 1999).
            Fouzder  et al, (1999) also reported that dried papaya skin could safely be used up to 90g/kg in the diet of growing pullets. It is also used in  ethno veterinary practices.

2.4  Medicinal and Pharmocological Properties
            Many biologically active phytochemical(s) have been isolated from papaya and studied for their action. Recently an antifungal chitinase  has been gene cloned and characterized from papaya fruit, (Krishna et al 2008). These chitinases have antibacterial activity. The purified chymopapein from commercially available spray dried latex of the fruit has shown immunological properties. (Fouzder  et al, 1999). The anthelmintic activity of papaya seed has been variously ascribed to carpaine (an alkaloid) and carpasemino (later identified as benzyl thiorea) and benzylisothiocyanate. Cysteine proteinases from papaya fruit have also been reported,(Krishna et al, 2008).

2.4.1               Medicinal Uses of Papaya Plant.
Parts :                                                            Uses
Latex:                         Anthelmintic, relieves dyspepsia, cures diarrhea, pain
                                    of burns and topical use, bleeding hemorrhoids.
Ripe fruit:                  stomachic, digestive, carminative, relieves obesity,
                                    bleeding pites, wounds of urinary tract, skin diseases.
Unripe fruit: laxative, diuretic, dried fruit reduces enlarged spleen
                                    and liver, antibacterial activity.
Seeds:                         carminative, emmenagogue, vermifuge, abortifacient, counter irritant, as paste in the treatment of ringworm and psoriasis, anti-fertility agents in males.
Seed juice:                 bleeding piles and enlarged liver and spleen.
Root:              Abortifacient, diuretic, checking irregular bleeding
                                    from the uterus, piles, anti-fungal activity.
Leaves:                      Young leaves as vegetable, jaundice (fine paste), 
urinary complaints and gonorrhea (infusion), dressing wounds (fresh leaves).
Flowers:                     Jaundice, emmenagogue, febrifuge and pectoral
Stem bark:                 Jaundice, anti-haemolytic activity, STD, sore teeth
                                    (inner bark), anti-fungal activity.
Source: Krishna et al (2008).
            Papaya seed also contain some alkaloids in their endosperm (Bolu et al, 2009). The leaves of papaya also contain magnesium, iron and potassium, which are essential nutrients and play an important role in the synthesis of aminoacids and proteins (Malik and Srivastava, 1982).

2.5 Antimicrobial properties/uses of papaya.
            The seeds of papaya has antimicrobial activity against Trichomonas vaginalis trophoziotes, ( Krishna et al, 2008). The seeds and pulp of papaya  was shown to be bacteriostatic against several enteropathogens such as Bacillus subtilis Enterobacter cloacae, Escherichia coli, Salmonella typhi, Staphylococcus aureus, Proteus vulgaris, Pseudomonas aeruginosa and Klebsiella pneumonia. Purified extracts from ripe and unripe fruits also produce very significant antibacterial activity on S. aureus, Bacillus cereus, E. coli, P. aeruginos and Shigella  flexneri ( Nwofia et al, 2002).
            The aqueous extract of papaya fruit exhibits anti-microbial activity and promotes significant wound healing ability in diabetic rats. The seeds of papaya  irrespective of stage of maturity have bacteriostatic activity on gram positive and gram negative organisms, which could be useful in treating chronic skin ulcers, (Marotta et al, 2006). The papaya seeds macerate has  clinical potential on conjugal and plasmid transfer from Salmonella typhimurium to Escherichia coli , both  invitro and in the digestive tract of genotobiotic mice, (Dominquez et al, 2008).
            Herbal containing papaya leaves and root or leaves alone as one of the constituents has antibacterial activity against Salmonella tyhii, S. paratyphi and S. paratyphi and S. typhii murium. However, water, acetone and ethanol extract of papaya leaves showed no microbiadal activity. (Krishna et al., 2008).

2.6       Organic Acid (orgacid)
            An organic acid is an organic compound with acidic properties The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxy1 group [-COOH-] (Dibner and Buttin 2002).  Organic acids are used in food preservation because of their effects on bacteria. The basic principle of the mode of action of organic acids on bacteria is that, non-dissociated (non-ionized) organic acids can penetrate the bacteria cell wall and disrupt the normal physiology of certain types of bacteria that refer to as pH sensitive” meaning that they cannot tolerate a wide range of internal and external pH gradient, (Dibner and Buttin 2002).

2.6.1   The Effect of  Organic Acid on  Gut Microflora of Broilers
            The antibacterial effect of orgacid was observed in the  study in which significant (P<0.05) reduction in the caecal population viability and coliform counts in birds fed organic based diet was recorded (Adil et al., 2011). Similar effects were observed by (Owens et al, 2008) and (Pirgozliev et al, 2008) reporting significantly (P<0.05) reduced total viable coliform numbers in the ileum and caecum of boiler chicken due to organic acid supplementation. (Gunal et al, 2006) also reported that the use of organic acid mixture significantly decreased the total bacterial and gram negative bacterial counts in broiler chicken. Mohanery and Mahzorieh (2005) recorded a decrease in E. coli population in the intestines of broiler chicken with malic acid.
            Apart from antimicrobial properties, organic acids have been shown to have beneficial effect on the intestinal mucosa of boiler chicken as well (Adil et al, 2011). Nutrient  absorption in the gut occurs from the intestinal mucosa and hence, manipulation there  may improve the nutrient utilization (Bradley et al, 1994, Savage et al, 1996, Pelicano et al, 2005) and consequently growth performance.

2.7       Understanding the Gut Microbial Ecology of Broilers
            The microflora in the gastrointestinal tract of boiler chickens influences digestions, health, and well being. Analysis of chicken gut microflora has been mainly by culture-based methods (Amit-Romach et al, 2004). Studies using these technique have been useful for the identification and analysis of specific groups of bacteria. However, the use of enrichment medium precludes even relative quantitation of bacterial species, (Amit-Romach, et al., 2004). Soumaya et al, (2011) reported that the use of ribosomal DNA-based molecular techniques make it possible to identify different bacterial populations in environmental samples without culturing.
            Anti-Romach et al., (2011) evaluated six bacterial species present in  chicken gut: Lactobacillus, Bifidobacterium, Salmonella, Campylobacter, E.coli and Clostridium. The authors reported that the major species present in the small intestines and caecum was Lactobacillus with a Bifidobacterium population becoming more dominant in the caecum of older birds. A review dedicated to the bacterial population in the digestive tract of chickens reported a predominance of Lactobacillus strains (68.7%) in the ileum and and jejunum followed  by strains of Streptococcus (6.6%) and Enterococcus (6.4%)  (Soumaya et al., 2011). They also reported that these proportions are statistically different in the cecum with Lactobacillus strains contributing only 8.2%, Streptotoccus 0.7%, and Enterococcus strains 1% of the bacterial population. However, different author reported different findings regarding the composition of the microbiota in the chicken digestive tract. Bjernum(2006) noted that Lactobacillus composed of only a small proportion (5 to 6%) while Domonceaux et al, (2006) reported a large number of Lactobacillus strains (25%) with a high degree of diversity. In addition, two studies also, indentified different species, with Bjerrum et al., (2006) reporting the presence of L. salvarius, L. agilis and L. ketasatonis and Dormonceaux et al., (2006), L. salivarius sub sp. Salivarus. However, Soumaya et al.,( 2011)  reported that the predominant caecal isolates of LAB were L.sakai, L. salivarius sub sp. Salivarus.
            However, Soumaya et al, (2011), reported the predominant Lactobacillus spp population isolated  were; L. sakai, L. salivarius , L. reteri,  L. curvatus. Other species included Weisella spp (16.6%) and Enterococcus spp (5.5%). The presence in the caecum of chickens of Weissella spp and Lactobacillus strains such as L. acidophilus, L. crispatus, L. reuteri and L. avianus has been reported by Lu et al, (2003).
            Amit-Romach et al (2004) reported that Clostridium was detected in some segments of the small intestine in young chicks. In older chickens, Salmonella, Campylobacter, E.coli species were found in the caeca.

2.8 Microbial Diversity along the digestive tract
            Analysis of the microbial luminal contents of the different sites in the small intestine examined indicated that among the six bacterial species examined, only Lactobacillus was consistently detected in all intestinal regions (Amit-Romach et al, 2004). They also reported that  at day four, most of the bacterial species were not detectable in the small intestines. Proportions of Lactobacillus changed little along the intestine at a young age. However, at 35 days of age the posterior segments exhibited lower levels of lactobacillus compared with the anterior segment of the intestine. In addition, at Day 25, E.coli and Clostridium were detected in the duodenum and ileum.
            However, the exact composition of the microbiota differs depends on the age, rearing environment, and diet of chickens (Soumaya et al, 2011). The authors also showed that the antagonism against Camphylobacter by the lactobacilli strains isolated from the chicken caecum could be attributed to the production of bacteriocin-like substances.
            Lactobacillus was the major species present in the duodenum of young chickens. Some clostridium species were found in the jejunum and ileum, as has been described previously in older chicks using culture methods (Amit-Romach et al, 2004). The population in the caecum was more varied, with some Salmonella and E. coli species occurring, as has been previously observed using culture and molecular  methods (Mead and Adams, 1977, Zhu et al, 2002). With advancing age, the small intenstine bacterial population still remained predominantly Lactobacillus, whereas in the caecum, Bifidobacterium began to develop and reached a stable proportion between 14 and 25 days (Amit-Romach et al, 2004).

2.9 The use of probiotics in Broilers Production
            The bacterial flora of the digestive tract is the first barrier that protects the host organism against pathogen colonization. The beneficial effect of lactic acid bacteria (LAB) exerted from probiotics on birds involves the colonization of the mucous membrane of different parts of the digestive tract, and protection of the mucous membrane against pathogenic bacteria (Brzoskol et al, 2007).  It was found that some species of lactic acid bacteria (e.g Enterococeus faecium) inhibit the growth of Salmonella pullorum, thus reducing the mortality of experimentally infected chickens (Audisio et al, 2000).
            Mulder et al, (1997) showed that at 19 weeks of age, birds fed corn-soya bean diets viable Lactobacillus (lacto) kg-1 diet (rccms-lacto diets) had better (P < 0.05) feed intake and body weight gain than those not receiving the treatment. Lactic acid bacteria produce a wide range of bacteriocins with antagonism against gram-negative and gram-positive bacteria including Campylobacter (Soumaya et al, 2011). Tortureo (1973), and Jernigan (2012) showed prebiotics addition in broilers diets to stimulate appetite, body weight gain and reduction in bacterial load on the gut of the birds.
            Tortureo (1973) reported results from a study in which broilers were fed a culture of L. acidophilus. Data collected were weight gain, feed conversion ratio, fat digestibility, nitrogen retention, caeca and faeces weight and  levels of the lactic acid bacteria flora and Enterococcus up to 15 days of age.  The results indicated that implantation of Lactobacillus, resulted in an effect similar to that observed in chicks fed probiotics and antibiotics.
             The implantation of L. acidophilus resulted in lower caeca and excreta weights. A distinct change in the bacterial flora in the caeca and small intestine also occurred. By nine days of age the population of Enterococcus had almost completely disappeared.
            Microbiology analyses of the small intestine digesta showed that lactic acid bacteria increased the intestinal counts of Enterococcus Streptococcus and Lactobacillus  compared with the unsupplemented control group  and with the antibiotic supplemented group (Brzokal et al, 2007). In the caecum, the Streptococcus, Escherichia coli and Clostridium counts were considerably reduced. No Salmeonella, Shigella, Campylobacter or clostridium  were found in the small instestine or in the caecum. These results corroborate those of earlier studies (Barnes et al, 1972) on the bacterial composition of the digestive tract of birds including birds receiving probiotic bacteria (Brzoska et al, 2007).
Share on Google Plus


The publications and/or documents on this website are provided for general information purposes only. Your use of any of these sample documents is subjected to your own decision NB: Join our Social Media Network on Google Plus | Facebook | Twitter | Linkedin