Education: Application of probiotic in Nigeria Aquaculture

OSUN STATE UNIVERSITY,  COLLEGE OF  AGRICULTURE,             
DEPARTMENT OF FISHERIES&WILDLIFE.
Seminar topic:
Review on Application of probiotics in Nigeria aquaculture.

BY:

AKANBI OLATUNBOSUN. I

FSR/2011/0004

Abstract
Aquaculture is the fastest growing food-producing sector in the world. Worldwide, people obtain 25% of their animal protein from fish and shellfish. A significant issue affecting aquaculture production in Nigeria is loss of stock through disease. When faced with disease problem, immediate response has been to use antimicrobial drugs. However, as a result of the growing awareness of the adverse effects of antibiotics and the increasing demand for environmental friendly aquaculture, the use of probiotics in aquaculture is now widely accepted. This review provides summary of benefits of probiotics, selection criteria, safety and evaluation of probiotics using molecular techniques. Current status, challenges and prospects in Nigeria aquaculture industry were also discussed.
Keywords: Probiotics, disease control, aquaculture, quality control, Nigeria.

INTRODUCTION
Aquaculture provided nearly 50 percent of the annual world fisheries production with 110 million tonnes of food fish in 2006. Half of all aquaculture production is fin fish, a quarter is aquatic plants and the remaining quarter is made up of crustacean (such as shrimp, prawn, crabs) and clam, oyster and mussels (FAO, 2007). Although aquaculture activity in Nigeria started about 50 years ago (Olagunju et al., 2007), aquaculture production in Nigeria is currently about 40,000 metric tonnes contributing only 6% of domestic fish production (Adeogun et al., 2007). Nigerians are high fish consumers and offer the largest market for fisheries production in Africa. Thus, Nigeria has become one of the largest fish importers in the developing world, importing about 600,000 metric tonnes annually (Olagunju et al., 2007). Fish production from captured fisheries in spite of its being expensive and risk due to the militancy activities in the coastal line regions of Nigeria has been erratic and on the decline in recent years. To solve the high demand for fish, aquaculture production remains the best option to bridge the wide gap  between fish demand and domestic production. Moreover, aquaculture expansion has been a slow process; private sector fish farmers have faced major constraints. Outside the problem of high cost of fish feeds and quality seed, disease outbreak is a major challenge in fish farming in Nigeria. The prevalence of disease under natural condition is usually low incidence because of the expanse of water and reduced risk of contact between parasite and fish (Hoffman and Bauer, 1971). However, under intensive management the crowded condition of large population of fish would result in heavy parasitic infection, disease and loss of fish (Qi et al., 2009). In recent decades, disease prevention and control have led to a substantial increase in the use of antibiotics. The wide and frequent use of antibiotics in aquaculture has resulted in the development and spread of antibiotic resistance. Because of the health risks associated with the use of antibiotics in animal production, there is a growing awareness that antibiotics should be used with more care (Defoirdt et al., 2011). The resistant bacteria can not only proliferate after an antibiotic has killed off the other bacterial, but also they can transfer their resistance genes to other bacterial that have never been exposed to the antibiotic (Verschuere et al., 2000). Resistance mechanisms can arise one  of  two  ways: chromosomal mutation or acquisition of plasmids. Chromosomal mutations cannot be transferred to other bacteria but plasmids can transfer resistance rapidly (Lewin, 1992). Several bacterial pathogens can develop plasmid-mediated resistance. At the high population densities of bacteria found in aquaculture ponds, transfer via viruses and even direct transformation from DNA absorbed to the particles in the water or on the sediment surfaces could all be likely mechanism for genetic exchange (Balcázar et al., 2006). In view of the above, the development of non-antibiotic agents is one of the key factors for health management in aquaculture. According to Browdy (1998), one of the most significant technologies that evolved in response to disease control problems is the use of probiotics. The application of probiotics in aquaculture is prevalent in United State of America, China, Japan, Indonesia, Thailand and European countries with commendable achievements. However, although the Nigerian aquaculture industry is expanding, the application and development of probiotics is very meager when compared to other countries. The purpose of this review is to describe the principles of benefits, safety and summarize recent applications of probiotics in Nigeria aquaculture. Thereby the increasing of the awareness that application of probiotics in Nigerian aquaculture has tremendous scope and a glorious future.
Probiotics; the concept
"Probiotics", "Probiont", "Probiotic bacteria" or "Beneficial bacteria" are the terms synonymously used for probiotic bacteria. The term, probiotic, simply means "for life", originating from the Greek words "Pro and "bios" (Gismondo et al., 1999). Probiotics were originally defined as "organisms and substances which contribute to intestinal microbial balance" (Parker, 1974). However, as new findings emerged, several definitions of probiotics have been proposed. According to Fuller (1989), Probiotics are "Live microbial feed supplement which beneficially affects the host animal by improving its intestinal balance". In 2001, a Joint Food and Agriculture Organization/World Health Organization Working Group on drafting "Guidelines for the evaluation of Probiotics in food" recommended that probiotics should be defined as " live micro organisms which, when administered in adequate amounts, confer a health benefit on the host" (FAO/WHO, 2001). The application of the above definitions in aquaculture, however, requires some revision. Verschuere  et al. (2000) proposed a modified definition of a probiotic as  "a live microbial adjunct which has a beneficial effect on the host by modifying the hostassociated or ambient microbial community, by ensuring improved use of the feed or enhancing its nutritional value, by enhancing  the host response towards  disease,  or by improving the quality of its ambient environment"  This broad definition of probiotics in aquaculture system was able to address the influence of immediate environment on the health of aquatic animals. Based on the above modified definition, probiotics are recognized as microbial adjuncts that;
Prevent pathogens from proliferation in the intestinal tract on the surface structures and in the culture system of cultured species.

• Aid maximum feed utilization.
• Improve water quality,
• Enhance the immune system of the host.

Presently, probiotics are common place in health promoting food for humans and also used as therapeutic, prophylactic and growth supplements in animal production and human health (Rinkinen et al., 2003; Senok et al., 2005; Anukam et al., 2005; Ng et al., 2009). The lactic acid bacteria (LAB) have been extensively used and researched for human and terrestrial animal purposes (Savadogo et al., 2006; Ukeyima et al., 2010). The most widely researched and used LAB are the lactobacilli and bifidobacteria (Ross et al., 2005; Senok et al., 2005). Other commonly studied probiotics include the spore forming Bacillus spp. and yeast Cutting (2011) have given a critical review of Bacillus probiotics and products for human use. The use of probiotics is now prevalent in the aquaculture industry as a means of controlling disease, improving water quality and enhancing the immune system of cultured species (Wang, 2007; Wang et al., 2008; Ma et al., 2009). Nowadays, a number of probiotic products are commercially available in aquaculture. However, very few of these products are available in Nigerian market.
Benefits of probiotics in aquaculture
Potential benefits of probiotics in aquaculture ponds includes: enhanced decomposition of organic matter, reduction in nitrogen and phosphorus concentrations, better algal growth, greater availability of dissolved oxygen, less cyanobacteria (blue-green algae), control of ammonia, nitrite and hydrogen sulfide, lower incidence of disease and greater survival of  shrimp and fish production. Although, some of the effects of probiotics have been documented clearly, research is still going on in the area with many questions about some of their benefits remaining unanswered. However, it is crucial to remember that different probiotic strains are associated with different health benefits (Senok et al., 2005).

1. Enhancement of the Immune Response
Among the numerous beneficial effects of probiotics, modulation of immune system is one of the most commonly  purported benefits of probiotics.  Fish larvae,  shrimps and other invertebrates have immune systems that are less well developed than adult stage and are dependent primarily on nonspecific immune responses for their resistance to infection (Söderhall and Cerenius, 1998; Verschuere et al., 2000). Previous studies on fish dealt with growth promoting and disease preventive ability of probiotics. However, recent attention has been shifted towards immunomodulating effects of probiotics in fish immune system. A lot of immunological studies have been performed in several fish using different probiotics and their potency to stimulate the teleost immunity both under in vivo and in vitro conditions is noteworthy (Nayak, 2010). Ogunshe and Olabode (2009) evaluated the ability of Lactobacillus fermentum LbFF4 isolated from Nigerian fermented food (fufu) and L. plantarum LbOGI from a beverage (Ogi) to induce immunity in Clarias gariepinus (Burchell) against some selected fish bacterial pathogens. Research has shown that several probitoics either individually or in combination with other probiotics can stimulate or enhance both systemic and local immunity in fish. Nayak (2010) critically reviewed the probiotics immunomodulatory activity and the factors that regulate the maximal induction of immune responses in cultured aquatic species.
2. Improvement of water quality
Nitrogenous compounds contamination such as ammonia, nitrite and nitrate in fish culture systems/ponds has been a serious concern. The susceptibility of cultured aquatic species to high concentration of these compounds is generally species-specific, but in high concentrations, these compounds may be extremely harmful and cause mass mortality in all cases. Ma et al. (2009) reported the ability of Lactobacillus spp. JK-8 and JK-11 simultaneously remove nitrogen and pathogens from contaminated shrimp farms. In several other studies, water quality has been improved by the addition of probiotics especially Bacillus spp. (Verschuere et al., 2000; Kolndadacha et al., 2009). The reason is that gram – positive Bacillus spp. according to Stanier et al. (1963) are generally more efficient in converting organic matter back to CO2 than gram – negative bacteria, which would convert a greater percentage of organic carbon to bacterial biomass or slime. Dalmin et al. (2001) reported that use of Bacillus spp. improved water quality, survival and growth rates and the health status of juvenile Penaeus monodon and reduced the pathogenic vibrios. Nitrification has been recognized to help in preventing build up of toxic ammonia. In water recirculatory system (WRS), the start –up of biofilters by transferring medium from an existing filter is a common practice. Nitrifers are responsible for the oxidation of ammonia to nitrite and subsequently  to    nitrate.      Aerobic    denitrifiers  are  considered to be good candidates to reduce nitrate and/or nitrite to N2 under aerobic conditions in aquaculture systems. In China, Liao et al. (2006) isolated a new aerobic denitrifying strain X0412 from shrimp ponds which was found to contain the nitrite reducdase gene nirs. FAO has now designated the use of probiotics as a major means for the improvement of aquatic environmental quality (Subasinghe et al., 2003; Qi et al., 2009).
3. Source of nutrients and enzymatic contribution to digestion
Probiotics have been suggested to have beneficial effects in the digestive processes of aquatic animals (Yanbo and Zirong, 2006; Balcázar et al., 2007). Sakata (1990) reported that Bacteroides and Clostridium spp. have contributed to host fish nutrition, especially by supply fatty acids and vitamins. Prieur et al. (1990) also reported that some bacteria may participate in the digestion processes of bivalves by producing extracellular enzymes, such as proteases, lipases, as well as providing necessary growth factors. Similar observation have been reported for microbial flora of adult penaeid shrimp (Penaeus chinensis), where a complement of enzymes for digestion and synthesized compounds that are assimilated by the animal (Wang et al., 2000). 
Probiotics selection criteria
Previous reviews have proposed favourable characteristics for the selection for cultured aquatic species (Fuller, 1989; Verschuere et al., 2000; Vine et al., 2006; Watson-Kesarcodi et al., 2008; Gómez and Balcázar, 2008; Kolndadacha et al., 2009), Merrifield et al. (2010) proposed an extended list of criteria for potential probionts which includes the following:-
Must not be pathogenic, not only with regards to the host species but also with regards to aquatic animal in general and human consumers.
Must be resistant to bile salts.
Should be able to adhere to and /or grow well within intestinal mucosa. Should characteristic. display advantageous growth Should exhibit antagonistic properties towards one or more key pathogens.
Should remain viable under normal storage conditions and robust enough to survive industrial processes.
Based on the outlined favourable characteristics of potential probiont, it is not easy to find a candidate that will satisfy all these characteristics, however, through the combined application  of  multiple  favourable  probiontic  candidates it may be possible to produce greater benefits in aquaculture than the application of single probionts.

Probiotics in aquaculture management
These organisms can be administered to the aquaculture management through feeding, injection or immersion of the probiotic bacteria (.Irianto A et al. 2002)




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