Effect of Aflatoxin Contaminated Feed on Energy Reserves of Fish Labeo Rohita (hamilton)

Effect of aflatoxin contaminated feed on glycogen content ofliver,blood glucose, total serum protein and blood urea of the fish Labeo rohita was studied. The result revealed that administration of aflatoxin decreased liver glycogen and tatal serum protein but blood level of glucose and urea increased.

In Teleost the level of glucose and protein is an indicator of stress in fishes.The major source of blood glucose is liver glycogen.The level ofurea in blood indicates the degree of damage to kidney and utilization of protein in the body.Aflatoxin is the metabolic by product of molds Aspergillus flavus and Aspergillus parasiticus on a variety of food such as cotton seed, corn, wheat, milk, fish meal etc.It is a toxic compound, a potent immunosuppressive and carcinogenic agent and the cause of high mortality in livestock, (Reed andKasali.,1987, Montessano et al.,1997).Due to growth requirement of the molds aflatoxin poses a greater risk in warmer climate.Effects of aflatoxin on fishes and other animals have been reported by many workers.Nunez et al. (1991) reported hepatocellular adenoma and hepatocellular carcinoma in Rainbow trout when exposed to aflaroxin B 1 .Caguan et al. (2004) reported loss of appetite, low survival percent and decreased mean total biomass in tilapia when fed with aflatoxin contaminated feed.Faisal et al. (2008) reported spermatotoxic effect of aflatoxin in male wister rat.Aflatoxin causes elevated blood glucose level in aflatoxin treated Nile Tilapia (El-Boshy et al., 2008).The extent of damage produced by aflatoxin depends upon the species, the toxin concentration and time period of the exposure (Coulombe et al., 1984;Centroducati et al., 2009;Sepahdari et al., 2010).In the present investigation effect of aflatoxin on glycogen content of liver, blood glucose level, total serum protein and blood urea level of Labeo rohita has been evaluated in order to explore the effect of toxin in the fish.

MATERIAlS AnD METHODS
The fish Labeo rohita was collected from river sone near Ara.72 fishes measuring about10 -20 cm and weighing about 30 -50 gm were selected and kept in twelve aquaria measuring 3 1 x 2 1 x 1 1 .Six fishes were kept in each aquarium.Three aquaria containing six fishes each were kept as control and nine aquaria containing six fishes each were kept as experimental set.

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Feed I or good feed contained 0% moldy feed or unmixed feed.Feed I were given to control.

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Feed II contained 10 % moldy feed and 90% good feed.Feed II were given to first set of experimental fishes comprising aquaria 2A, 2B and 2C.

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Feed III contained 50% good feed and 50% moldy feed.Feed III were given to second set of experimental fishes comprising three aquaria 3A, 3B and 3C.

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Feed IV contained 100% moldy feed.Feed IV were given to fourth set of fishes comprising three aquaria 4A, 4B and 4C.
Moldy feed were prepared in laboratory.The commercial fish feed was first sprinkled with small amount of tap water to make the feed moist and then infected with cultured Aspergillus flavus by mixing 10 ml of cultured Aspergillusflavus.The inoculation was made in a transfer chamber to avoid contamination.The mixed feed was then covered with a plastic sack.The infected feed was kept in a condition which is favourable for the growth of mold.
Required amount of moldy feed and good feed were weight carefully for each treatment and then mixed thoroughly.The fish were fed a day after and daily there after two times a day at 8.00 am and at 6.00 pm at a feeding rate of 4% of the body weight .
The quantitative estimation of glycogen content of liver was estimated according to a modified method of Kemp and Andrein (1954).Blood glucose was estimated by O. Toluidine method of Cooper and McDanile (1970).Quantitative estimation of total serum protein was done according to the method of Kinsley (1942) followed by Mehl (1945) and Weichselbaum (1946).Blood urea was quantitatively estimated according to the Phenol hypochlirite method using the Berthelot Reaction (Fawcet and Scott 1960; Chaney and Marbach 1962).

RESUlT AnD DISCUSSIOn
The glycogen content of liver was 31.9 +0.24 mg/g in control and that of experimental fish fed with feed IV(100 % moldy feed) was 22.0 + 0.24 mg/g.The blood glucose level was observed as 71.5 + 0.69mg/100ml in control and 101.3 + 1.49 mg/100ml in fishes given feed IV.Thus there was a significant(p>0.05)and gradual decline in the content of liver glycogen and a simultaneous rise in the blood glucose observed in the experiment fish when aflatoxin contamination increased in the food.Thus the present findings are in agreement with those of Nunez et al.(1991) 2012) reported significant increase in cortisol level and significant decrease in insulin level in aflatoxin treated fish Clariuslazera.An increase in cortisol level increases glycogenolysis in liver.In the present investigation liver glycogen level is low and blood glucose level is high in fishes fed with aflatoxin contaminated feed which indicates that the increase in blood glucose level is probably due to increased liver glycogenolysis.Also the increase in blood glucose level may also be attributed to decrease in secretion of insulin as an effect of aflatoxin, which in turn reduces the process of glycogensis resulting in rise of blood glucose level.In addition the rise in blood glucose many also be due to gluconeogenic breakdown of protein to form glucose for energy production to be utilized in detoxification process at the time of stress induced by aflatoxin.
Thus in the present investigation depletion of liver glycogen and increase in blood glucose might have resulted due to increased glycogenolyis, gluconeogenesis and decreased glycogenesis as an effect of dietary aflatoxin mediated by increased cortsol and decreasedinsulin level under the condition of stress.
In the present study there was a gradual fall in total serum protein and a simultaneous rise in the blood urea level with the increase in the aflatoxin contaminated feed in the food.The present findings are in agreement with Pepeljnjak et al.(2003) inrainbow trout,El-Boshy at al. (2008) and Shehata at al.(2009) in O.niloticus.Martinez et al. (2004) reported that fish under stress may mobilize protein to meet energy requirement needed to sustain increase physiological activities.
Since fishes have a very little amount of carbohydrate ( Rao, 1999), the next alternative source of energy is protein to meet the increased energy demand under the condition of stress.Buhlar et al. (2000) reported that exposure to mycotoxin decreases protein synthesis in Onchorhynchus mykiss.Aflatoxin causes loss of appetite resulted in hypophagia and this might have also caused the decrease in total serum protein level.
The serum urea level showed an increase with increase in aflatoxin contaminated feed.A rise in Bllood urea level indicates to abnormal kidney function (Newberne 1981).Similar findings were reported by Zaki et al. (2008Zaki et al. ( , 2010) ) in aflatoxin treated fishesTilapia nilotica and Tilapia zilli .Increase in urea level due to necrosis in kidney was reported by Mansfeld (1989), Pier(1987).Thus in the present studies aflatoxin might have caused necrosis in kidney resulting in increase in urea level.