The Toxicological Effect Of Ochratoxin A On Weaned Piglets And The Involved Mechanism

Ochratoxin A(OTA)contamination is a worldwide problem in pig industry.It is produced in foodstuffs by Aspergillus in subtropical and tropical areas and by Penicillium notably in temperate and colder zones.OTA can contaminate a wide variety of foodstuffs,including cereals,coffee,grapes,meat and derivatives,especially in storage period.OTA is nephrotoxic,hepatotoxic,teratogenic and immunotoxic to several species of animals,and was classified as a possible human carcinogen(group 2B)by the International Agency for Research on Cancer in 1993.Maximum permitted levels in foodstuffs have been established by sereval countries.Pork is the major meat we consume in China.As people pay more attention on food safty,it is important to keep pork free of hazardous substance.OTA contamination in raw mateials of feed is very common.This may have bad effects on growth performance and health status of pigs,which reduce economic benefit of pig farms and finally affect human health.While most researches on OTA are about determination methods,and in vivo researches in pigs are rare.This study was conducted to investigate the toxicity of OTA on pigs and the involved mechanism.We feed weaned piglets on OTA contaminated diet for 6 weeks to find out the effects of OTA intake on OTA residue in serum and tissues,growth performance,serum biochemical parameters,antioxidant capacity of blood and tissues and apoptosis-related genes expression of tissues of weaned piglets,in order to provide theoretical basis for preventing OTA intoxication.Experiment 1.Production and determination of ochratoxin AOTA was produced in shredded corn from Aspergillus ochraceus(CGMCC3.04411)for two weeks.Measure the OTA concentration of the moulded ground corn and basal diet used in the following experiments by LC-MS/MS.The moulded ground corn contained 20μg OTA/g and OTA was not detected in the basal diet.The moulded ground corn was mixed in the basal diet to feed the weaned piglets in experiments 2,3 and 4.Experiment 2.Effect of OTA concentration in diet on OTA residues in serum and tissues of weaned piglets36 five weeks old weaned piglets(Landrace*Yorkshire*Duroc,3 replicates per group and 4 piglets per replicate)were randomly divided into three groups and fed with basal diet(control group),basal diet added with 0.4 mg OTA/kg(low dose group),and basal diet added with 0.8 mg OTA/kg(high dose group).Feeding experiment lasted for 42 days.Blood samples were collected on days 0,14,28 and 42 and kidney,liver and spleen samples were collected on day 42 to measure OTA concentration.OTA concentration in serum and tissues of piglets in both low dose and high dose groups were significantly higher than control group(P<0.01).In OTA fed groups,OTA concentration was the highest in serum,followed by kidney,liver and spleen.Experiment 3.Effect of OTA on growth performance,serum biochemical parameters and hispathology of weaned pigletsExperimental design is the same as experiment 2.Body weights were obtained on days 0 and 42 to analyse growth performance.Blood samples were collected on days 0,14,28 and 42 to measure serum biochemical parameters.Kidney and liver samples were collected on day 42 to make hispathological slices.Average daily gain and average daily feed intake significantly decreased in both OTA fed groups compared with control group(P<0.05).Feed/gain ratio significantly increased in both OTA fed groups compared with control group(P<0.05).Biochemical parameters showed significant increase in AST,AST/ALT(P<0.05),creatinine and urea,and significant decrease in glucose,total protein,albumin and globulin(P<0.05).Degenerative changes were seen in the epithelial cells in proximal tubules and hepatocytes in periphery of lobules of weaned piglets in OTA fed groups.Experiment 4.Effect of OTA on antioxidant capacity and apoptosis status of weaned pigletsExperimental design is the same as experiment 2.Blood samples were collected on days 0,14,28 and 42 to measure antioxidant capacity.Kidney,liver and spleen samples were collected on day 42 to measure antioxidant capacity and apoptosis-related genes expression.Serum MDA content in OTA fed groups and kidney MDA content in high dose group significantly increased compared with control group(P<0.05).Serum SOD activities in both OTA fed groups and kidneys of piglets in high dose group significantly decreased compared with control group(P<0.05).GSH levels of erythrocytes and kidneys in high dose group significantly decreased compared with control group(P<0.05).mRNA expression of bcl-2 increased and mRNA expression of bax decreased slightly but not significantly in liver,kidney and spleen.The ratio of mRNA expression of bcl-2 and bax in liver and kidney significantly increased in high dose group compared with control group(P<0.05).This experiment showed that OTA intake can decrease antioxidant capacity and apoptosis status.