The Toxic Effects And Tissue Accumulation Of Dietary Cadmium In Growing-finishing Pigs

This study was conducted to investigate the effects of dietary cadmium on growth performance,blood biochemical parameters,antioxidant capacity,organ pathology and pork quality,to clarify the toxicity and tissue accumulation of cadmium.Exp.1 The toxicity and accumulation of dietary cadmium in growing pigsThe purpose of this trial was to determine the effects of different dietary cadmium levels on growth performance,blood biochemical parameters,antioxidant capacity and tissue cadmium deposition in growing pigs preliminarily.Thirty-five DLY pigs with initial body weight(BW)of 24.97 ± 0.6 kg were randomly allotted to 5 treatments with 7 replicates of 1 pigs per replicate,5 treatments were fed with 0,5,10,20 and 40 mg/kg cadmium containing diet respectively for 28 days.At the end of this trial,the control and 40 mg/kg group were selected to obtain blood samples via the jugular veins and slaughtered.Results showed that there were no significant effects on growth performance of growing pigs(P>0.05).Compared with control group,dietary 40 mg/kg cadmium increased the content of TP(P<0.05),but decreased the urea nitrogen content in serum(P<0.01).There was no significant effect on serum antioxidant capacity(P>0.05).The contents of cadmium in renal cortex,renal medulla,liver and muscle of 40 mg/kg group were 27.047,12.048,8.097 and 0.282 mg/kg,which have exceeded the limited standard and significantly higher than the control group(P<0.01).This trial indicated that dietary cadmium had no significant effects on growth performance and serum antioxidant capacity of growing pigs,but high dose cadmium(40 mg/kg)resulted in excessive accumulation of cadmium in pig tissues.Exp.2 The toxicity and tissue accumulation of dietary cadmium in growing-finishing pigsThis trial was intended to further explore the relationship between dietary and tissue cadmium based on experiment 1,and to investigate the effects of dietary cadmium on growth performance,apparent nutrient digestibility,serum biochemical and immunoglobulin parameters,antioxidant capacity,tissue pathology and meat quality in growing-finishing pigs.Forty DLY pigs with initial body weight(BW)of 25.06±1.0 kg were randomly allotted to 5 treatments with 8 replicates of I pigs per replicate,5 treatments were fed with 0,0.5,2.5,12.5 and 25.0 mg/kg cadmium containing diet respectively for 98 days.Pigs were weighed and blood samples via the jugular veins were collected on 28th,63th and 98th days and all slaughtered at end of the trial.The results are as follows:1.There were no significant effects on growth performance among groups(P>0.05).2.There were no significant effects on apparent nutrient digestibility in different groups(P<0.05).3.The cadmium contents in tissues increased with the increasing cadmium levels in dietary.The liver and kidney were the main accumulation organ,which showed a quadratic function curve,and their contents were close to or beyond the limit standard.Meanwhile,the cadmium in muscle was relatively small and under the limit standard.The threshold value of dietary cadmium is 0.73 mg/kg by equation.4.When compared with the control group,25.0 mg/kg group had a higher serum ALB level on 28th day(P<0.01),a lower AST level on 63th day(P<0.01),and a higher GLB level on 98th day(P<0.05).The TP level of 12.5 and 25.0 mg/kg group increased on 98th day compared with the control group(P<0.05).5.The serum CAT,SOD and GSH-Px activities in the three phases showed a first increased and then decreased trend with the increasing dietary cadmium levels.When compared with the control group,2.5 and 12.5 mg/kg groups had a higher CAT activities on 28th day(P<0.05).When compared with the control group,25.0 mg/kg group had a lower MDA level(P<0.05),while 2.5 and 12.5 mg/kg group had a higher CAT activities(P<0.05)on 63th day,a higher SOD activity in 12.5 mg/kg group(P<0.05)and a lower SOD activity in 25.0 mg/kg group(P<0.05)along with a higher GSH-Px activity in 0.5 mg/kg group(P<0.05)and a lower GSH-Px activity in 25.0 mg/kg group(P<0.01)were also obscrved.When compared with the control group,the CAT activities increased in 0.5 and 12.5 mg/kg group(P<0.01),SOD activities decreased in 2.5,12.5 and 25 mg/kg group(P<0.01),and GSH-Px activity increased in 12.5 mg/kg group on 98th day(P<0.01).6.There were no significant effects on serum IgG level(P>0.05).When compared with the control group,25.Omg/kg group had a higher IgM level on 63 th day(P<0.01),and a higher IgM level on 98th day compared with the other four groups(P<0.01).7.Dietary cadmium had no significant effects on organ index(P>0.05),but it could cause vacuolar degeneration of liver cells as well as the swelling and shedding of renal tubular epithelial cells.The hepatic sinusoid expanded and the renal interstitium focal inflammatory cells infiltrated in 25.0 mg/kg group.8.When compared with the control group,25 mg/kg group had a higher L*value(P<0.05)and a lower a*value(P<0.01)at 24h,while there was no significant difference in muscle shear force,pH value,b*value,drip loss and cooking loss among groups(P>0.05).This trial indicated that dietary cadmium had no significant effects on growth performance,nutrient digestibility and organ index in growing-finishing pigs.With the increasing cadmium levels in diet,serum antioxidant capacity presented a first stimulation and then inhibition effect,while some biochemical and immunoglobulin parameters showed a stimulation effect.High level of cadmium caused a certain degree of pathological damage to the liver and kidney,and also had an adverse effect on meat color.The main accumulation sites were liver and kidney,and kidney could exceed the limit standard when dietary cadmium beyond 0.73 mg/kg.To sum up:in this experiment,a high dose and short-term or a relative low dose and long-term trial both had no significant effects on the growth performance of pigs,but it had stimulating and inhibiting effects on serum biochemical,antioxidant and immune indexes.Cadmium caused liver and kidney damage,and had adverse effects on meat color.Liver and kidney,the main accumulation sites,could exceed the limit standard when chronic exposure to the diet with at least0.73 mg/kg of cadmium.