PAT June, 2014; 10 (1): 38-52 ISSN: 0794-5213 Online copy available at www.patnsukjournal.net/currentissue Implication of Aflatoxin In Fish Feeds and Management Strategies For Sustainable Aquaculture Sotolu, A.O *1, Sule, S.O 2, Oshinowo, J.A. 3 and Ogara I. M 4 1 Department of Forestry, Wildlife and Fisheries, Nasarawa State University, keffi, Shabu-Lafia campus, P.M.B. 135, Lafia, Nigeria. 2 Department of Aquaculture and Fisheries Management, University of Ibadan, Ibadan, Nigeria. 3 Department of Vocational Studies, Emmanuel Alayande college of Education, Oyo. 4 Department of Agronomy, Nasarawa State University, keffi, Shabu-Lafia campus, P.M.B. 135, Lafia, Nigeria. * Corresponding Author: sotoluola@yahoo.com Abstract Successful fish production has continued to be bedeviled with myriads of problems. Despite high costs incurred on fish feed production, aflatoxins caused by Aspergillus flavus and A. parasiticus are great threat to the eventual use of the expensive feed. They are capable of impacting high mortalities of fish and consequently heavy loss to farmers. Prevailing storage condition, use of plant protein sources in aquafeed production and relatively high tropical weather situation work in favour of high occurrence of aflatoxicosis recorded in Nigeria. Factors that increase the production of aflatoxins in feeds include environmental temperatures above 27 C, humidity levels greater than 62%, and moisture levels in the feed above 14% especially during storage. The extent of contamination varies with geographic location, processing and feed storage practices. Improper storage is one of the most important factors favouring the growth of aflatoxin-producing molds, and it is a major element that the fish producer need to control. International trade has been reported affected by cases of aflatoxins contamination and several aquafeed ingredients and finished feeds are known to be susceptible to aflatoxins. It is of great importance therefore that all stakeholders in the aquaculture industry be on the alert to arrest cases of aflatoxicosis immediately once it is inevitable thereby averting crisis on the farm and save-guard human health. Management of aflatoxins can be achieved by focusing on moisture content regulation in feed ingredients during processing and finished feeds at storage. Good hygiene of ingredients processing, machines and the environment is highly recommended as well as use of mold inhibitors and copper sulphate among others. Keywords: Aflatoxins, Aquaculture, Moisture contents, Molds, Storage condition Introduction Aflatoxin is a toxic compound produced by Aspergillus flavus and A. parasiticus. The molds can grow in improperly stored feeds and feeds with inferior quality of ingredients. Aflatoxins represent a serious source of contamination in foods and feed in many parts of the world (Murjani, 2003). Aflatoxicosis is a disease that can affect many species of fish and shellfish and results when feed contaminated with aflatoxins is eaten
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 39 by the fish (Ashley, 1970; Hernández et al., 2005; Bautista et al., 1994). The first documented incidences of aflatoxicosis affecting fish health occurred in the 1960s in trout hatcheries. Domesticated rainbow trout (Oncorhynchus mykiss) that were fed a pelleted feed prepared with cottonseed meal contaminated with aflatoxins developed liver tumors (Ashley, 1970) and as much as 85% of stock of fish died in another hatchery as reported by Taniwaki (2001) in a similar instance. In tropical and subtropical conditions, this potential is further increased due to storage under humid and hot conditions. International trade has been reported affected by such commodities affected by exposure to aflatoxins given worldwide concerns as the economic impacts are enormous (Golan and Paster, 2008). Four major aflatoxins (AFB 1, AFB 2, AFG 1 and AFG 2 ) are direct contaminants of grains and finished feeds including fish pellets. Aflatoxin B 1 is known to be the most significant form that causes serious risk to animals and human health. The carcinogenic effect of aflatoxin B 1 has been studied in fishes such as salmonid, rainbow trout, channel catfish, tilapia, guppy and Indian major carps (Jantrarotai and Lovell, 1990; Lovell, 2001; Tacon, 1992; Wu, 1998; Chavez et al., 1994; Murjani, 2003) and Penaeus monodon (Bautista et al., 1994). Factors that increase the production of aflatoxins in feeds include environmental temperatures above 27 C (80 F), humidity levels greater than 62% and moisture levels in the feed above 14%. The extent of contamination will vary with geographic location, feed storage practices and processing methods. Improper storage is one of the most important factors favoring the growth of aflatoxin-producing molds and it is a major element that can be controlled by the fish producer (Payne et al., 1988). Rainbow trout and nile tilapia are extremely sensitive to AFB 1, while channel catfish are much less responsive (Jantrarotai and Lovell, 1990; Tuan, 2001). The Rainbow trout was widespread in the Province of West Azarbajan. This condition was observed in several farms which administered moldy feeds to their fish. Interview with farmers indicated that moldy feed was caused by high moisture content and improper storage of their feeds. Fish feed occupy about 75% of the total cost of fish production (Lovell, 1992). Despite this obvious fact some of the already prepared fish feeds and/or ingredients become wasted as a result of Aflatoxin contamination since they are unhealthy for fish consumption. The resultant effect of Aflatoxin on fish feed will lead not only to high cost of production but also, decrease in total farm production. Improper feed storage is detrimental to fish production as it can result in economic loss when the feed is no longer fit for fish consumption and increase in the cost of production due to medication of affected fish and such economic wastage should be allowed to persist. The review aimed at recreating the conscience and awareness of stakeholders in the aquaculture industry regarding socio-economic problems associated with incidence of aflatoxins on farms and suggesting practical ways of its successful management.
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 40 Aflatoxins and Aflatoxicosis Aflatoxicosis is a disease that can affect many species of fish, and results when feed contaminated with aflatoxins is eaten by the fish (Ashley, 1970). Aflatoxins are chemicals produced by some species of naturally occurring fungi (Aspergillus flavus and Aspergillus parasiticus) commonly known as molds. Aflatoxins are common contaminants of oilseed crops such as cottonseed, peanut meal, and corn. Wheat, sunflower, soybean, fish meal, and nutritionally complete feeds can also be contaminated with aflatoxins. Four major aflatoxins (AFB1, AFB2, AFG1 and AFG2) are direct contaminants of grains and finished feeds. Factors that increase the production of aflatoxins in feeds include environmental temperatures above 27 C, humidity levels greater than 62%, and moisture levels in the feed above 14%. The extent of contamination will vary with geographic location, feed storage practices and processing methods. Improper storage is one of the most important factors favouring the growth of aflatoxin-producing molds, and it is a major element that the fish producer needed to control. Importance of Aflatoxins In Aquaculture Aflatoxins can cause disease indirectly through their effects on essential nutrients in diet. For example fat soluble antioxidants such as vitamin C (necessary for immune function) and thiamin (necessary for metabolism nervous function) in feed can be destroyed by those toxins. Hence, it is not surprising that aflatoxins depress the immune system, making fish more susceptible to bacterial, vital or parasitic diseases (Herrera, 1996). Those subtle effects often go unnoticed and profits are lost due to decreased efficiency in production, slow growth rate, reduced weights of the fished product, wastage of fish feed and increased medical cost (Ferguson, 1989; Tacon, 1992; Wu, 1998; Royes and Yanong, 2002). However when fish eat feed contaminated with aflatoxins, different kinds of adverse conditions can be observed in fish such as; i. Liver tumor (Ashley, 1970) ii. Reduced growth and appetite (Royes and Yanong, 2002) iii. Tissue abnormality or lesion in the livers (Wu, 1998) Aflatoxins can cause about 60% of the total fish mortality in any production system (Tuan, 2001). AFB I contaminated feed result to reduced weight gain and reduced red blood cell counts when fed to fish (Nile Tilapia) (Chavez et al., 1994). The extent of disease, caused by consumption of Aflatoxins depends upon the age and species of the fish. Fry are more susceptible to Aflatoxicosis than adults and some species of fish are sensitive to Aflatoxins than others (Jantrarotai and Lovell, 1990). Other livestock that can also be affected by aflatoxicosis include: swine, horses, dairy cattle etc. Table 1
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 41 presents among summary of signs of feed contaminated with aflatoxins while Table 2 shows signs of aflatoxicosis in fish respectively. Table 1: Signs of Feed Contaminated With Aflatoxins Signs i) Feed stored for a longer time and probably contaminated with molds appear stale. Reference Ashley (1970) ii) Contaminated feed are discoloured Ashley (1970) iii) Contaminated feed lump together and smell musty. Lovell (1992) iv) The presence of blue/grey mold on feed, stale feed are often saturated with moisture and appear to sweat. Smith (2005) Table 2: Signs of Aflatoxicosis in Fish Signs Reference i) Pale gills Wu (1998) ii)impaired blood clotting Chavez et al. (1994) iii) Anemia Ferguson (1989) iv) Prolong feeding of concentration of AFBI causes liver Ashley (1970) tumours which appear as pale yellow lessons and can spread to kidney. v) Poor growth rate and lack of weight gain. Royes and Yanong (2002) vi) Increase in fish mortality (higher Number of dead fish) Tuan (2001) maybe observed vii) Fin and tail rot Chavez et al. (1994) viii) Aflatoxin contaminated feeds results in eye opacity Chavez et al. (1994) leading to cataract and Blindness. Implications of Aflatoxins in Fish Feeds Aflatoxin B 1 has been the most extensively studied. Twenty to 200 ppb will cause a decrease in feed intake and growth performance, which can be partially offset by increasing specific dietary nutrients such as lysine or methionine. In severe cases (1,000 to 5,000 ppb) of aflatoxicosis, one can expect acute effects including death. Aflatoxin B1 (AFB 1 ) is one of the most potent, naturally occurring, cancer-causing agents in animals. Conditions increasing the likelihood of acute
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 42 aflatoxicosis in humans include limited availability of food, environmental conditions that favor fungal development in crops and commodities, and lack of regulatory systems for aflatoxin monitoring and control. It has been known that aflatoxins, especially aflatoxin B1, are potent carcinogens in fish, some animals and man (Fig. 1). The expression of aflatoxin-related diseases in humans may be influenced by factors such as age, sex, nutritional status, and/or concurrent exposure to other causative agents such as viral hepatitis (HBV) or parasite infestation. In tropical and subtropical conditions, this potential is further increased due to storage under humid and hot conditions. International trade in affected commodities and exposure to aflatoxins are worldwide concerns and the economic impact due to animal losses can be enormous. Aflatoxicosis and resulting epizootic hepatoma have been reported among a wide range of fish where Aspergillus species-contaminated foodstuffs are incorporated into the diet. Aflatoxin B 1 (AFB 1 ) is among the most potent known hepatotoxins and carcinogens. Therefore, it is an important potential toxicant to the most of the popularly cultured fish species. Figure 1: Pathways and consequences for aflatoxin in animal metabolism Source: Eaton et al. (1993)
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 43 Increased Danger of Aflatoxicosis Aflatoxin production is the consequence of a combination of species, substrate and environment. The factors affecting aflatoxin can be divided into three categories: environment, nutritional and biological factors. Physical factors include temperature, ph, moisture, light, aeration and level of atmospheric gases. Aflatoxins are produced only between temperatures of 12 and 14 C and the optimal temperatures is 25 to 35 C (Asis et al., 2002). However, interest in the toxic effects on cultured warm-water fishes, such as tilapia (Oreochromis spp.) and catfish (Clarias gariepinus), has increased as diets for these species are now being formulated to contain more plant and less animal ingredients towards least-cost feed production as well as the existing tropical weather conditions suitable for its occurrence in Nigeria. This increases the potential for development of aflatoxicosis in these species because, plant ingredients have a higher potential than animal ingredients for contamination with aflatoxins. Human Exposure to Aflatoxin. Two main populations of exposure exist in the world. In countries with commercial food systems the rate of exposure is generally low because the food system allows the levels of exposure to be regulated to <10 ppb, and managed, and the economic conditions in these countries allow for the additional costs and capital requirements to achieve these levels to be absorbed, and production methods that minimize the risk to be adopted. In the countries where these economic conditions do not exist there is little protection of people from the toxin even where regulations do exist. However, the level of exposure is such that only occasionally does acute illness and death from aflatoxicosis occur, and the majority of exposure seems to be at the chronic level. i. Acute Exposure to Aflatoxin. The incidents of poisoning and death from AF that are reported serve to indicate that AF is a risk in most developing countries. Some example reports of death and serious illness from AF are consolidated in table 3. Table 3: Cases of Outbreaks of Acute Aflatoxicosis. Country References Malaysia Cheng (1992) Taiwan Shank (1977) India Van Rensburg (1977); Shank (1981) Kenya Cheng (1992)
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 44 ii. Chronic Exposure to Aflatoxin. Two main approaches have been used to measure the extent of exposure to AF in people in developing countries. The first approach has been the use of food samples collected either from prepared meals, ingredients, or the market. The most reliable sample source for a measure of 58 exposures is analysis of prepared meals, since people may sort grain and remove those that are considered unfit to eat. Data from this approach shows that exposure in many countries of the developing world is potentially high. Variations exist between countries largely as a function of diet. Data collected by Hall and Wild (1993) reports the levels of exposure (ng/kg/day) to AF based on food samples in the following countries as being: Kenya (3.5-14.8), Swaziland (5.1-43.1), Mozambique (38.6-183.7), Transkei (16.5), The Gambia (4-115), southern Guangxi (11.7-2027), Thailand (6.5-53), compared with the USA (2.7). Independently, Awuah (2000) estimated the exposure in Ghana to be 9.9-99.2 ng/kg/day, based only on peanut consumption. Other commonly consumed corn-based foods (Kenkey) are also known to be contaminated (Kpodo, 1995; Hell et al., 2000), so the exposure is likely to be higher. The currently favored method of measuring human exposure is by the analysis of body fluids for the presence of AF derivatives (Pier et al., 1985; Wild and Pisani, 1998). Prevention and Management of Mycotoxins In Farms Prevention in Silages Prevention of mycotoxins in silages includes following accepted ensiling practices aimed at inhibiting deterioration primarily through elimination of oxygen. Some silage additives (such as ammonia, propionic acid, microbial cultures, or enzymatic silage) may be beneficial in preventing mycotoxins because they are effective at reducing mold growth (Asis et al., 2002). Silo size should be matched to herd size to ensure daily removal of silage at a rate faster than deterioration. Feed bunks should be cleaned regularly. Care should be taken to ensure that high moisture grains are stored at proper moisture content and in a well-maintained structure (Asis et al., 2002). Prevention of Feed Contamination Controlling mold growth and mycotoxin production is very important to the feed manufacturer and livestock producer. Control of mold growth in feeds can be accomplished by keeping moisture low, keeping feed fresh, keeping equipment clean, and using mold inhibitors (Pier et al., 1985). Grains and other dry feed such as hay should be stored at a moisture level 14 percent or less to discourage mold growth. Aeration of grain bins is important to reduce moisture migration and to keep the feedstuffs dry (Pier et al., 1985).
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 45 Moisture in Feed Ingredients Moisture is the single most important factor in determining if and how rapidly molds will grow in feeds. Moisture in feeds comes from three sources namely; feed ingredients, feed manufacturing processes and the environment in which the feed is held or stored. In order to control the moisture content of feeds successfully, moisture from all three sources must be controlled. Since corn and other grains are a primary source of the moisture and molds found in feed, the first important step in controlling moisture in feed is to control it in the grains from which the feed is prepared (Pier et al., 1985. Since all feed ingredients contain moisture, they should be monitored and their moisture content controlled. It is commonly believed that the amount of moisture in grain is too small to permit mold growth except in rare and unusual circumstances. However, moisture is not evenly distributed in grain kernels. A batch of grain containing an average of 15.5 percent moisture may, for example, contain some kernels with 10 percent moisture and others with 20 percent moisture (Jarvis, 2008). The moisture content of individual grain kernels is directly related to the amount of mold growth that occurs: that is, kernels with higher moisture contents were more susceptible to mold growth. In addition to moisture, the amount of mold growth is about five times greater for broken kernels than for intact kernels. Thus the fraction of commercial grain, known as broken kernels and foreign matter, can be expected to have a higher mold and mycotoxin content than the portion composed of whole kernels. Moisture in Feed Manufacturing Processes Grains are commonly ground with a hammer mill to aid in mixing and handling, to improve digestibility, and to improve the pelleting process. This grinding process creates friction, which causes heat to build up. If unchecked, temperature increases greater than 10 degrees Fahrenheit will cause significant migration of grain moisture encouraging mold growth (Jarvis, 2008). This is particularly true in cold weather when temperature differences cause moisture to condense on the inside walls of bins. Airassisted hammer-mill systems reduce heat buildup in the product and, in turn, reduce moisture problems. The pelleting process involves mixing steam with the feed, pressing the mixture through a die, and then cooling the pellets to remove heat and moisture. Generally, heat and 3 to 5 percent moisture are added to the feed during the pelleting process in the form of steam. If the pelleting process is done correctly, this excess moisture is removed from the feed before shipment. If, however, this excess moisture is not removed when the pellets are cooled, mold growth will be encouraged. Since feeds containing moisture are warmer than normal, storing hot or warm pellets in a cool bin will cause moisture to condense on the inside of the bin. Although pelleting of feed has been shown to reduce mold counts by a factor of 100 to 10,000, many mold spores remain in the feed after it has been pelleted. After pelleting, the remaining spores can
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 46 grow if conditions are right. Thus the pelleting process delays, but does not prevent the onset of mold growth and plays only a minor role in efforts to control molds (Jarvis, 2008). In addition, pelleted feeds may be more easily attacked by molds than nonpelleted feeds. Moisture and Feed Storage Environment The moisture content of the substrate and temperature are the main factors regulating fungal growth and mycotoxin formation (Jarvis, 2008). In order t-o control mold growth, obvious sources of moisture in the feed processing and storage equipment must be eliminated. These sources may include leaks in feed storage tanks, augers, roofs (either at the barn or at the feed mill), and compartments in feed trucks. A fact about feed moisture often overlooked is that it changes in relation to the feed's environment. Since animals kept in confinement housing add moisture to their environment by respiration and defecation, the air in these houses can be very humid. Feed that was initially very low in moisture content will gain moisture when placed in a humid environment. The humidity in confinement housing should therefore be controlled by providing adequate ventilation. Koehler (1938) established that a moisture content of 18.3% on a wet weight basis was the lower limit for the growth of A. flavus in shelled corn and this was corroborated by the reports of Sanders et al., (1968) and Taniwaki (2001). Keeping Feeds Fresh Time is required for both mold and mycotoxin production to occur (Sanders et al., 1968). It is therefore important to have feeds delivered often so that they will be fresh when used. Feeds should generally be consumed within 10 days of delivery. It is equally important to manage the feed delivery system to ensure that feeds are uniform in freshness. Feed store should be managed in a first-in-first-out principle. The feed next to the wall is last to exit the store and therefore stays in the store the longest. The feed in contact with the wall is also the only portion of the feed that changes appreciably due to temperature. These factors make feed in contact with the wall susceptible to moisture migration and mold growth. It is best to maintain two feed stores so that one store can be completely emptied and cleaned before it is refilled with new feed Koehler (1938). Equipment Cleanliness When feed is manufactured and delivered to farms, it may come in contact with old feed that has lodged or caked in various areas of the feed storage and delivery systems. This old feed is often very moldy and may "seed" the fresher feed it contacts, increasing the chances of mold growth and mycotoxin formation. To prevent this problem, caked,
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 47 moldy feed should be removed from all feed manufacturing and handling equipment such as grinder, hammer mill, pelleting machine etc. it was revealed that, the farms which had executed the hygienic principals of stocking, showed lower levels of toxin in the diet and vice versa (Motalebi et al., 2008). Use of Mold Inhibitors The use of chemical mold inhibitors is a well-established practice in the feed industry. However, mold inhibitors are only one of several tools useful in the complex process of controlling the growth of molds, and they should not be relied upon exclusively. The main types of mold inhibitors are (1) individual or combinations of organic acids (for example, propionic, sorbic, benzoic, and acetic acids), (2) salts of organic acids (for example, calcium propionate and potassium sorbate), and (3) copper sulfate. Solid or liquid forms work equally well the inhibitor is evenly dispersed through the feed (Eaton et al. 1993). Generally, the acid form of a mold inhibitor is more active than its corresponding salt. Dispersion Many factors influence the effectiveness of mold inhibitors, and proper attention to these factors can enhance the benefits they provide. Mold inhibitors cannot be effective unless they are completely and thoroughly distributed throughout the feed. Ideally, this means that the entire surface of each feed particle should come in contact with the inhibitor and that the inhibitor should also penetrate feed particles so that interior molds will be inhibited. The particle size of the carriers for mold-inhibiting chemicals should be small so that as many particles of feed as possible are contacted generally, the smaller the inhibitor particles the greater the effectiveness (El-Sayed and Khalil, 2009). Some propionic acid inhibitors rely on the liberation of the chemical in the form of a gas or vapor from fairly large particle carriers. Presumably, the inhibitor then penetrates the air spaces between particles of feed to achieve even dispersion. Effect of Feed Ingredients Certain feed ingredients may also affect mold inhibitor performance. Protein or mineral supplements (for example, soybean meal, fish meal, poultry by-product meal, and limestone) tend to reduce the effectiveness of propionic acid. According to Eaton et al. (1993), these materials can neutralize free acids and convert them to their corresponding salts, which are less active as inhibitors. Dietary fat tends to enhance the activity of organic acids, probably by increasing their penetration into feed particles. Certain unknown factors in corn also alter the effectiveness of organic acid inhibitors.
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 48 Time Dependence When mold inhibitors are used at the concentrations typically recommended, they in essence produce a period of freedom from mold activity. If a longer mold-free period is desired, a higher concentration of inhibitor should be used. The concentration of the inhibitor begins to decrease almost immediately after it is applied as a result of chemical binding, mold activity, or both (Sanders et al., 1968). When the concentration of the inhibitor is reduced until it is incapable of inhibiting mold growth, the mold begins to use the inhibitor as a food source and grows. In addition, feeds that are heavily contaminated with molds will require additional amounts of inhibitor to achieve the desired level of protection. Influence of Pelleting The widespread use of pelleted feeds in the feed industry is beneficial to the use of mold inhibitors. The heat that the feed undergoes during pelleting enhances the effectiveness of organic acids. Generally, the higher the pelleting temperature, the more effective the inhibitor. Once mold activity commences in pellets, however, it proceeds at a faster rate than in non-pelleted feed because the pelleting process that makes feed more readily digestible by animals also makes it more easily digested by molds. Copper Sulfate The practice of recommending copper sulfate as a treatment for fungal diseases in animals goes back many decades. The effectiveness of copper as a mold inhibitor is difficult to document. Although copper sulfate in the diet has been shown to improve body weight and feed conversion efficiency in broilers, excessive levels of copper may be toxic to young animals and will accumulate in the environment (Eaton et al. 1993). In addition, recent research has indicated that feeding copper sulfate to poultry causes the formation of mouth lesions similar to those formed by some mycotoxins. Similar mouth lesions might be formed in other animal species. The use of inorganic binders/clays Mineral clays to Chemi-bind mycotoxins, and prevent them from being absorbed by the animal's GIT, has received a lot of research attention recently. These clay products (which include zeolites, bentonites, and bleaching clays and hydrated sodium calcium aluminosilicates [HSCAS]) have been shown to change the responses of rats to Zearalenone and T-2 toxin (Eaton et al., 1993). However, it should be clearly understood that binding of some mycotoxins may be weak or nonexistent and that clay products differ in their ability to bind mycotoxins. While HSCAS products has been shown to bind aflatoxin protecting animals against aflatoxicosis, they have not shown to possess binding affinity to Fusarium Toxins.
PAT 2014; 10 (1):38-52: ISSN: 0794-5213; Sotolu et al;; Implication of Aflatoxin In Fish Feeds. 49 Mycotoxin Sampling, Testing, and Test Kits Since mycotoxins are not evenly distributed in grain or in mixed feeds, taking a feed or grain sample which will give a meaningful result in mycotoxin analyses is difficult. Grab samples generally give very low estimates of mycotoxin content. In fact, nearly 90 percent of the error associated with mycotoxin assays can be attributed to how the original sample was collected. This is due to only 1 to 3 percent of the kernels in a contaminated lot containing mycotoxin, and these contaminated kernels are usually not evenly distributed within the lot of grains. For whole kernel grains, a properly taken composite sample of at least ten pounds is required for a reasonably accurate, mycotoxin analysis (Eaton et al., 1993). Trucks can usually be sampled with a grain probe, but bins must often be sampled as grain is being withdrawn. Analytical techniques for the detection of mycotoxins continue to improve. Several commercial laboratories now test for a variety of mycotoxins. Although analytical costs can be a constraint, these costs may be insignificant compared with the economic consequences of production and health losses associated with mycotoxin contamination. Commercial antibody test kits for screening or quantitation are currently available for aflatoxins, zearalenone, deoxynivalenol (DON), T-2 toxin, ochratoxin A, and fumonisins. These antibody methods, while they are still being improved, are good if used properly. Conclusion and Recommendations To prevent aflatoxicosis, follow manufacturer`s recommendations regarding shelf-life and try to determine the feed manufacture date and storing feeds ingredients and finished feeds under optimum condition of moisture content not greater than 14% should be observed. Regular testing for aflatoxins is a good idea. Simple on-farm inspection can be done visually (look for the presence of blue/grey mold on feed) or with a black light which may cause a bright greenish/yellow fluorescence if A. flavus is present. Avoid using feeds that appear discolored, lump together and smell musty. Clean feed storage bins and automatic feeders regularly. Aflatoxins lower production efficiency of cultured fish by reducing growth rates, impairing immunity and in some cases, causing colossal mortality. Storing feed properly (in a cool, dry area on pallets and at least one foot away from any walls) can prevent unnecessary economic losses and avoid health hazards in man. Effective control of aflatoxicosis in farm animals can be achieved by the addition of small amounts of certain clays to feeds, protecting the animals from contamination that would otherwise result in economic losses. This is a really cheap technology and could rapidly change human exposure to the toxin.
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