| The effect of layer silicate nanoparticles (LSN) on adsorption and elimination of dietary cadmium was investigated in crucian, Carassius auratus. Moreover, the changes on intestinal microflora of crucian were demonstrated by using Cu (Ⅱ)-exchanged silicate nanoparticles (CSN).Experiment I:One hundred and eighty crucian with an average weight of (20.68±1.1) g were selected and divided into 4 groups. Each group was replicated 3 times with 15 crucian per replicate. The experiment was lasted for 60 days. The 4 groups were denominated as follows:control group (basic dietary with 0.19 mg/kg cadmium), trial group 1 (basic dietary added with 0.5%LSN), trial group 2 (basic dietary added with 120 mg/kg cadmium), trial group 3 (basic dietary added with 120 mg/kg cadmium and 0.5% LSN).ExperimentⅡ:One hundred and thirty-five crucian with an average weight of (20.68±1.1) g were selected and divided into 3 groups. Each group was replicated 3 times with 15 crucian per replicate. The experiment was lasted for 60 days. The 3 groups were denominated as follows:control group (basic dietary), trial group 1 (basic dietary added with 50 mg/kg aureomycin), trial group 2 (basic dietary added with 0.5% LSN).The results of experiment I was shown below:1. The ADG of trial group 3 was significantly increased compared to that of trial group 2 (P< 0.05). No differences on growth performance and feed coefficient were observed between control group and trial group 1 (P> 0.05).2. Compared with control group, the content of cadmium in muscle, kidney, intestine and liver of trial group 1 were significantly increased by 58.1%(P< 0.05),74.1% (P< 0.05),70.3%(P< 0.05) and 75.0%(P< 0.05), respectively. Compared with trial group 2, the content of cadmium in muscle, kidney, intestine and liver of trial group 3 were significantly decreased by 35.5%(P< 0.05),21.6%(P< 0.05), 31.0%(P< 0.05) and 42.2%(P< 0.05), respectively.3. The content of metallothionein (MT) in liver, intestine and muscle of trial group 2 were enhanced by 12.1%(P< 0.05),116.0%(P< 0.05) and 62.3%(P< 0.05), respectively, compared to that of control group. However, the content of MT in liver, intestine and muscle of trial group 3 were decreased by 6.7%(P< 0.05), 26.9%(P< 0.05) and 25.0%(P< 0.05), respectively, compared to that of trial group 2.4. Anti-oxidative enzyme and MDA activities were also analyzed. Compared with control group, the activities of T-AOC, CAT, GSH-Px and GSH in trial group 2 were decreased by 26.0%(P< 0.05),18.2%(P< 0.05),8.3%(P< 0.05) and 34.6%(P< 0.05), respectively. Compared with trial group 2, the activities of T-AOC, CAT, GSH-Px and GSH in trial group 3 were increased by 32.4%(P< 0.05),14.2%(P< 0.05),6.8%(P< 0.05) and 33.2%(P< 0.05), respectively. The activity of serum MDA in trial group 3 was decreased by 17.5%(P< 0.05) compared to that of trial group 2. It was indicated that LSN could reduced the oxidative damage induced by cadmium.5. Compared with control group, the activities of serum T3 and insulin in trial group 2 were decreased by 44.9%(P< 0.05) and 50.6%(P< 0.05), respectively. The activities of serum T3 and insulin in trial group 3 were enhanced by 36.6%(P< 0.05) and 85.6%(P< 0.05), respectively, which compared with trial group 2. It was revealed that to a large extent, the blight effect of cadmium on related endocrine organs was avoided by supplementation of LSN.6. No significant differences on content of Fe, Cu and Zn in liver, kidney, spleen, intestine and blood, respectively, were performed between control group and trial group 1 (P> 0.05). Compared with control group, the content of Fe in liver, kidney, intestine, muscle and blood of trial group 2 were reduced by 20.6%(P< 0.05),17.2%(P< 0.05),35.3%(P< 0.05),30.8%(P< 0.05) and 14.5%(P< 0.05), respectively. Compared with trial group 2, the content of Fe in liver, kidney, intestine, muscle and blood of trial group 3 were significantly increased by 15.5% (P< 0.05),9.2%(P< 0.05),26.0%(P< 0.05),41.4%(P< 0.05) and 7.2%(P< 0.05), respectively. Compared with control group, the content of Cu in liver, kidney, spleen, bone and blood of trial group 2 were significantly increased by 213.2%(P<0.05),273.4%(P< 0.05),65.2%(P< 0.05),4.9%(P< 0.05) and 63.1%(P< 0.05), respectively. Compared with trial group 2, the content of Cu in liver, kidney, spleen, bone and blood of trial group 3 were reduced by 26.8%(P< 0.05),28.2%(P< 0.05),19.5%(P< 0.05),3.6%(P< 0.05) and 21.2%(P< 0.05), respectively. In conclusion, to some extent, the interference of cadmium on trace element could be eliminated by the action of LSN.7. The activity of Na+-K+ATPase in liver of trial group 2 was decreased by 37.5%(P < 0.05) compared to that of control group. Compared to trial group 2. the activity of Na+-K+ATPase in liver of trial group 3 was enhanced by 20.0%(P< 0.05). Compared to trial group 2, the activities of GPT and GOT in trial group 3 were reduced by 14.7%(P< 0.05) and 11.9%(P< 0.05), respectively.8. Observed by optical microscopy, in the trial group 2, the inter-glomerular was more intangible and the glomerular basement membrane was become thicker than that of control group. Moreover, the connective tissue was largely proliferated and the gap between layer and visceral of renal capsule was significantly shrunk in the trial group 2. However, the pathological damage of kidney in trial group 3 was lightened. It was indicated that the damage to crucian kidney induced by cadmium could be significantly reduced by LSN.The results of experimentⅡwas shown below:1. Compared with control group, the ADG of trial group 2 (LSN supplementation group) was enhanced by 19.47%(P< 0.05), while the feed coefficient was decreased by 14.79%(P< 0.05). Compared with trial group 1 (aureomycin supplementation group), the ADG of trial group 2 was increased by 7.14%(P< 0.05), while the feed coefficient was reduced by 7.44%(P< 0.05).2. The total amount of bacteria, pathogenic vibrio and Escherichia. coli in trial group 2 were decreased by 22.34%(P< 0.05),26.83%(P< 0.05) and 27.89%(P< 0.05), respectively, which compared to control group. Compared with trial group 1, the total amount of bacteria, pathogenic vibrio and Escherichia. coli in trial group 2 were decreased by 10.77%(P< 0.05),11.39%(P< 0.05) and 17.16%(P< 0.05), respectively. Compared with control group and trial group 1, the amount of lactobacillus was enhanced by 23.05%(P< 0.05) and 12.48%(P< 0.05), respectively. Moreover, compared with control group, the total amount of bacteria, pathogenic vibrio and Escherichia. coli in trial group 1 and 2 were all decreased, while the number of lactobacillus were all increased (P> 0.05).3. Compared with control group, the activities of trypsinase and lipase in liver of trial group 1 were enhanced by 5.0%(P< 0.05) and 72.7%(P< 0.05), while those of trial group 2 were increased by 31.4%(P< 0.05) and 20.2%(P< 0.05) compared to trial group 1. However, the activity of amylase in liver in trial group 1 and 2 were improved with no significant differences (P> 0.05).4. The villus width and height was increased in trial group 1 and 2 by observation of the morphology of intestine. Compared with control group, the villus height of foregut, midgut and hindgut in trial group 1 were increased by 9.4%(P< 0.05), 27.5%(P< 0.05) and 19.8%(P< 0.05), respectively. Compared with trial group 1, the villus height of foregut, midgut and hindgut in trial group 2 were increased by 8.7%(P< 0.05),17.8%(P< 0.05) and 20.6%(P< 0.05), respectively.5. The activities of serum lysozyme in trial group 1 and 2 were increased by 17.0% (P< 0.05) and 68.5%(P< 0.05), respectively, when compared with control group. Moreover, the activity of serum lysozyme of trial group 2 was higher than that of trial group 1, which was increased by 44.0%(P< 0.05).6. Compared with control group, the activities of Na+-K+ATPase in liver of trial group 1 and 2 were enhanced by 37.5%(P< 0.05) and 41.7%(P< 0.05), respectively, while those in gill were increased by 13.6%(P< 0.05) and 22.7%(P < 0.05), respectively. Compared with control group, the activities of Ca-Mg ATPase in gill of trial group 1 and 2 were increased by 13.7%(P< 0.05) and 15.7%(P< 0.05), respectively. However, no differences of Ca2+-Mg2+ATPase activity in gill were found between trial group 1 and 2 (P> 0.05).7. Compared with control group, the content of albumin in trial group 1 was increased by 30.7%(P< 0.05), while the content of total protein and albumin in trial group 2 were enhanced by 62.6%(P< 0.05) and 53.1%(P< 0.05), respectively. The content of MUN in trial group 2 was decreased by 36.9%(P< 0.05) when compared with control group. Compared with trial group 1, the content of total protein and albumin in trial group 2 were increased by 37.2%(P< 0.05) and 17.1%(P< 0.05), respectively. The content of MUN in trial group 2 was reduced by 18.6%(P< 0.05) when compared with trial group 1.
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