Study On Layer Silicate Nanoparticles To Reduce The Retention Of Lead In Finishing Pigs

This study was conducted to evaluate the effectiveness of nanometer silicate (PBNK) to absorb Pb²⁺ using Caco-2 cell model in vitro and the security of PBNK, and approach the feasibility of PBNK eliminating dietary lead using finishing pigs (Duroc×Landrace×Yorkshine) by detecting its protection against adverse effect of lead on growth performance, apparent digestibility of nutrients, lead residues in tissues and meat color.The main results are as follows.The selective adsorption of Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Fe²⁺ on PBNK at certain condition in solution showed that Pb²⁺ showed the strongest affinity for it while others ions hardly showed affinity.The results of cell culture trial showed that different concentration PBNK have no difference on cell proliferation rate and releasing LDH in different time (p＞0. 05). 40～80mg/L Pb²⁺ significantly increased releasing LDH (p＜0.05) , reduced cell proliferation rate (p＜0.05) and damaged the cellular morphology in time-dose dependent manner. When simultaneously supplementation of lead and PBNK, cell proliferation rate and cellular morphology of Caco-2 cell hold normal.The results of feeding trial indicated that ADG, ADFI in 10mg/kg Pb exposed group decreased by 16.13% (p＜0.05), 6.85% (p＜0.05), F/G increased by 10.91% (p＜0.05) compared to control. ADG, ADFI in 10mg/kg Pb+0.5%PBNK adding group increased by 16.44% (p＜0.05), 5.61% (p＜0.05), F/G reduced by 9.04% (p＜0.05) compared to 10mg/kg Pb adding group.The determination of lead residues in tissues indicated that muscle, liver and renal of control were 0.45, 1.44, 1.79μg/g, and beyond the standard of European Union on foods, respectively. When 0.5% PBNK was added to basal diet , lead retention in these organs reached EU standards. The lead retentions in muscle, heart, spleen, pancreas, lung, brain, bone and hair decreased by 80% (p＜0.01),32.50%(p＜0.05),49.12%(p＜0.05),45.901%(p＜0.05),59.09%(p＜0.01),38.89%(p＜0. 05),70.0%(p＜0. 01),60.0%(p＜0.01) compared with the control group. After 0.5%PBNK supplemented to diet, the concentrations of lead in muscle, liver, kidney, boold, heart, spleen, pancreas, lung, brain, bone and hair evidently decreased (p＜0.05) respectively in comparison with the group supplemented with 10mg/kg Pb only.Compared to control, supplemented with 0.5% PBNK only significantly increased the Pb concentration in feces by 51.0%(p＜0.05), and lowed the Pb level in urine by 81.9%(p＜0.01). After simultaneously supplementation of lead and PBNK, Pb content in feces significantly was enhanced by 67.65%(p＜0.05), the Pb concentration in urine was evidently reduced by 86.76%(p＜0.01) compared with the group supplemented with 10mg/kg Pb only.The apparent digestibility of nutrients showed that the digestibility of crude protein, Ca and P in Pb group were evidently decreased compared to the control group. When 0.5% PBNK was added to the 10.0mg/kg diet, the digestibility of crude protein, Ca and P improved 7.03% (p＜0.05 ), 10.55% (p＜0.05 ) and 11.12% (p＜0.05), respectively.The analysis of trace element in tissues indicated that pigs fed the diet adding 10mk/kg Pb only had lower Fe, Ca, Zn, Cu concentrations in liver, kidney, long bone than those of control (p＜0.05), which were improved significantly by PBNK supplemented to the diet (p＜0.05).The results of serum sample showed that GOT and GPT in Pb group improved by 16.97%(p＜0.05), 17.55%(p＜0.05),respectively, which were decreased by the level of control with PBNK supplemented to the diet (p＜0.05). The group of feeding the diet supplementing 0.5% PBNK had higher Ca, P and AKP levels in serum than the control (p＜0.05). In addition, after supplemented PBNK to the 10.0mg/kg Pb diet, the levels of Ca, P and AKP significantly improved 32.96%(p＜0.05),19.87%%(p＜0.05),24.85%(p＜0.05), respectively.The results of antioxidation capacity showed PBNK lowered MDA levels in serum and liver (p＜0.05), promoted the activities of CAT, SOD, GSH-Px (p＜0.05) respectively compared to control. MDA contents in serum and liver of 10mg/kg Pb+0.5%PBBA group also evidently were reduced (p＜0.05), the activities of CAT,SOD, GSH-Px (p＜0.05) were increased (p＜0.05) respectively compared to 10mg/kg Pb exposure group. In summary, all the results implied that PBNK, a kind of higher selective lead adsorbent , were secure to epithelia, which could effectively reduce the gastrointestinal absorption of lead, with a consequent reduction of lead residues in body tissues, alleviated adverse effects of lead on growth performance, apparent digestibility, meat quality, haematogenous function, anti-oxidative ability, and so on. No doubt it would be of great significance to apply PBNK to solve the problem of lead pollution in animal production industry. PBNK had provided an encouraging solution to produce safe and low-residue animal products with lead contaminated feed.