Continuation of Application of probiotic in Nigeria Aquaculture

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Application in feed
Probiotics are applied with the feed and a binder (egg or cod liveroil) and most commercial preparation contain either Lactobacillus sp or Saccharomyces cerevisiae (Abidi A. et al. 2003).According to FAO and WHO guidelines ,probiotic organisms used in food must be capable of surviving passages through the gut i.e. they must have the ability to resist gastric juices and exposure to bile (Senok Ac. Et al. 2005). Furthermore they must be able to proliferate and colonize the  digestive tract and they must be safe, effective and maintain their effectiveness and potency for the duration of the shelf life of the product. 
Direct application to pond water
The water probioics contain multiple strains of bacteria like Bacillus acidophilus, B. subtilis B. lecheniformis, Nitrobacter sp, Aerobacter and Sacharomyces cerevisiae. Application of probiotic through water of tanks and ponds may also have an effect on fish health by improving several qualities of water, since they modify the bacteria composition of the water and sediments (Ashraf  Ali, 2000, Venkateswara AR, 2007).

Application through injection
Application of probiotics by injection is a possibility. (Austin et al., 1995) suggested the possibility of freeze-drying the probiont like vaccine and applied either through bathing, or injection. (Yassir et al. 2005, Noh SH. Et al., 1994) has demonstrated the experimental administration of probiotic Micrococcus luteus to Oreochromis niloticus by injection through intra peritoneal route which had only 25% mortality as against 90% with Pseudomonas using the same route. According to (Yassir et al. 2005) the use of probiotics stimulate Rainbow trout immunity by stimulating phagocytes activity, complement mediated bacterial killing and immunoglobulin production (Noh SH. Et al., 1994).

Safety and evaluation of probiotics 
It is important to note that the safety profile of a potential probiotic strain is of critical importance in the selection process. Therefore, safety considerations of the putative probiotic strain should be taken into account as an integral part of process for the development and marketing of probiotics (Courvalian, 2006). Safety is the state of being certain that adverse effects will not be caused by an agent under defined conditions (Wang et al., 2008). As the search for probiotic bacteria continues, novel species and more specific strains of probiotic bacteria are constantly identified. It cannot be assumed that these new probiotic organisms share the historical safety of tested or traditional strains. Prior to incorporating them into products, new strains should be carefully assessed and evaluated for both safety and efficacy. Evaluation should include consideration for the end product formulation since this can induce adverse effects in some subjects or negate the positive effects altogether. A better understanding of the mechanism by which probiotic organisms might cause adverse effects could help to develop effective assays that predict which strains might not be suitable for use in probiotic products. Furthermore, modern molecular techniques should be applied to ensure that the species of probiotics used in aquaculture are correctly identified for quality assurance as well as safety. Conventional methods relying on phenotypic characterization, growth requirements and characteristics, fermentation profiles, and serology studies have been proven useful but carry inherit deficiencies (Qi et al., 2009). Presently, various molecular finger printing techniques using different genetic markers have been proven useful in strain differentiation. These techniques have been successfully applied in evaluating commercial probiotics in human foods (Fasoli et al., 2003; Temmerman et al., 2003, Huys et al., 2006). In Nigeria, reports on the identification and evaluation of probiotic bacteria and products using molecular techniques are rare. However, recent report by Hu and Yang (2006) using enterobacterial repetitive intergenic consensus – polymerase chain reaction (ERIC-PCR) and polymerase chain reaction – denaturing gradient gel electrophoresis/temperature gradient gel electrophoresis (PCR-DGGE/TGGE) to analyze microbial fertilizers showed that these methods are fast and accurate. Thus, there is urgent necessity for researchers in Nigeria to incorporate these sensitive and reliable molecular methods to identify and characterize the microbial content of probiotic products. In addition to PCRDGGE/TGGE techniques, improved FISH techniques (CARD-FISH,      FISH-MAR,        RING-FISH),  terminal  restriction fragment length polymorphism (T-RFLP), multilocus sequence typing (MLST) and fluorescence amplified fragment length polymorphism (F-AFLP) are available and can be applied in probiotic studies.

  CONCLUSION AND RECOMMENDATION 
Probiotics are important natural ingredients in finfish aquaculture and they have numerous beneficial effects: improved water quality, improved activity of gastrointestinal microbiota, and enhanced immune status, growth performance and feed utilization. Thus, probiotics have much potential to increase the efficiency and sustainability of agricultural production.  Nigerian aquaculture industry is expanding, however, the development and application of probiotics is very meager when compared to other countries. There is need for scientist in Nigeria to continue screening for novel probiotic strains from local aquaculture rearing systems to suit the specific requirement in Nigeria. In addition, screening and identification should not only be based on conventional methods, molecular techniques which have been shown to be fast and accurate should be applied. Since limited commercial probiotic products for aquaculture are in the Nigerian market, there is need for commercial production of putative probiotics. Also, issue of safety should not be over looked. 
REFERENCES
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