| This study was conducted to investigate the effectiveness of nanometer magnesium-aluminum mixed oxides (MAO) to adsorb dietary excessive fluoride of growing pigs on the basis of better adsorptive capacity of MAO in vitro, and approach the protection of MAO against adverse effects of fluoride on growth performance, apparent digestibility of nutrients, fluoride residues in tissues, endocrine function, immune indexes, antioxidation system function and the function of main organs.Ninety-six Duroc × Landrace × Yorkshire crossbred growing pigs(48 barrows and 48 gilts, respectively), with similar initial weight 24.14 ±1.12 kg, were randomly allotted to two supplementation of fluorine (0 and 150.0 mg/kg, as NaF; control and F) and two levels of MAO(0 and 0.2%; MAO and F+MAO) in a 2×2 factorial arrangement of treatments. Each treatment was fed corn-soybeen basal diet and consisted of three pens (replications) of eight pigs (sex balanced). The feeding experiment lasted for eighty-four days after seven days of adaptation period. The content of fluorine was 50.0 mg/kg in the basal diet. Ten days before ending of the feeding trial, digestion experiment was conducted by the method of total fecal collection. The 24 animals (sex balanced) were kept in individual pens and given their respective experimental diets. At the end of the feeding trial, eight pigs (four barrows and four gilts) from each treatment were randomly selected based on the similar body weight and slaughtered. Blood and organ samples were collected and determined for corresponding indexes.The main results were follows:The results of adsorptive experiment in vitro indicated that fluorine could be better adsorbed on MAO in some conditions. When pH was between 2 and 8, the largest amount of fluorine adsorbed was 763.98 mg/kg, and which happened at pH=4. The results showed that temperature, and Cl, Br and I in the same solution had no effects on effectiveness of fluorine adsorbed. The adsorptive capacity of MAO was steady. Desorption didn't appeared when pH changed from 2 to 8. Both Langmuir and Freundlich equations could be used to describe the adsorptive process.The results of feeding trial showed that ADG in F decreased by 8.22% compared to control (P<0.05), and that in F+MAO improved by 8.09% (P<0.05) compared with F. F/G in F was higher by 8.11%(P<0.05) than control, and that in F+MAO decreased by 6.88% (P<0.05) compared with F. There were no differences on ADG and F/G between MAO and control (P>0.05).The results of digestion experiment showed that the digestibility of dry matter, crude protein, calcium and phosphorus in F decreased by 8.96%(P<0.05), 11.17%(P<0.05), 16.59%(P<0.05) andl0.17%(P<0.05), respectively, compared to control. Those in F+MAO improved by 9.11%(P<0.05), 10.43%(P<0.05), 19.0%(P<0.05) and 12.71%(P<0.05) compared with F. There were no effects of fluorine and MAO on digestibility of EE and CF (P>0.05).The determination of fluorine residues in soft tissues showed that fluorine residues in muscle, liver, kidney and fat of MAO decreased by 30.71%(P<0.05), 49.35%(P<0.05), 40.80%(P<0.05) and 38.60%(P<0.05) respectively, compared to control. The contents of fluorine in muscle, liver, kidney and fat when 150 mg/kg fluorine added were 2.26, 3.67, 3.12 and 2.67mg/kg respectively, and beyond the highest standards of China on foods. When 0.2% MAO added to F treatment, fluorine residues in corresponding tissues decreased by 42.04%(P<0.05), 56.13%(P<0.05), 41.35%(P<0.05) and 37.45%(P<0.05). Fluorine retentions in immune organs, heart, brain, and other organs of MAO were lower than control (PO.05), respectively. Those in all above organs of F+MAO significantly decreased compared to F (P<0.05).Fluorine residues in skeletal tissues showed that the content of fluorine in teeth of MAO decreased by 30.71%(P<0.05) compared to control, which in F+MAO decreased by 71.22%(P<0.05) compared to F. Fluorine retentions in crania, zygoma, rib, vertebra, tibia, metacarpus, phalange of MAO were significantly lowered than control (P<0.05). Those in F+MAO decreased compared to F (P<0.05).The contents of fluorine in serum, bile, hair and urine indicated that fluorine retentions in MAO were lowered than control (P<0.05), and those in F+MAO were also significantly lowered than F (PO.05). Fluorine concentrations in feces of MAO increased by 42.04%(P<0.05) compared to control, which of F+MAO increased by 42.74%(P<0.05) compared to F.The results of determination on immune indexes showed that relative weight of immune organs in F significantly changed (P<0.05), which in F+MAO significantly improved than F (PO.05). PHA stimulation index of lymphocyte, IgA and IgG levels in serum of F decreased compared to control (PO.05). Those in F+MAO improved compared to F (PO.05). Addition of MAO had no effects on the immune function of animals (P>0.05).Results from antioxidation system function showed that MDA levels in serum, liver and kidney significantly increased compared to control (PO.05). Those in F+MAO significantly improved than F (PO.05). The contents of SOD, GSH-Px, CAT, XOD, GSTand CP of serum, liver and kidney of F significantly changed than control (P<0.05), which significantly improved in F+MAO compared with F (PO.05). There were no effects of MAO added to basal diet on all above antioxidation indexes (P>0.05).The analysis of endocrine function indicated that the levels in serum T3, TSH, T and LH in F significantly changed than control (P<0.05), which improved by MAO added to the 150 mg/kg fluorine treatment (P<0.05). There were no differences on all above indexes between MAO and control (P>0.05).The levels of iron, copper, zinc and manganese in tissues indicated that four trace elements levels in most tissues of F were significantly lowered than control (P<0.05). Those in F+MAO were higher than F (P<0.05). The results also showed that addition of 0.2% MAO had no effects on the contents of trace elements in tissues (P>0.05).The contents of calcium, phosphorus in tissues showed that excessive fluoride affected the metabolism of calcium and phosphorus. The contents of calcium and phosphorus in most tissues of F significantly changed than control (PO.05). Those in F+MAO improved than F (P<0.05). There were no differences on the contents of calcium and phosphorus of tissues between MAO and control (P>0.05).The results of the levels of DNA, RNA and protein in liver and kidney showed that the contents of RNA and protein, the ratio of RNA/DNA in liver and kidney of F significantly decreased compared with control (P<0.05), and which in F+MAO improved (P<0.05). There were no differences between MAO and control (P>0.05). There were no effects of fluorine and MAO on DNA levels in tissues (P>0.05).The results of histopathological examination revealed that it was found by optical microscope that shape of liver lobules was irregular, array of liver cell cords was changed and it was unclear among lobules in F. It was observed by optical microscope that significant atrophy of glomeruli, and swellings of kidney follicle, extensive vacuolization in renal tubules. Similarly, Cardiac muscle and the viii of jejunum in F were damaged by optical microscope. These changed were improved in F+MAO.
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