| The study was conducted to evaluate solubility of chromium nanoparticle (CrNano) in swine intestinal pH condition and its effects of on growth performance, carcass characteristics and meat quality in finishing pigs and approach to the mechanism.CrCL3, CrNano, Cr piconiate (CrPic) and Cr nicotinate (CrNic) were dissolved to different concentration as 100,200,400,800,1600 ppb in 0.9% NaCl solution. Cr concentration was determined after adjusting the pH to 8.5. 150 finishing pigs were divided into five groups based on ancestry, sex and weight,each of which included three replicates of 10 pigs each. The treatment groups received the same basal diet,supplemented with 0, 100, 200 and 400 μg/kg Cr from CrNano and 200 μg/kg Cr from CrCl3.6H2O respectively. The pigs were fed experimental diet for 35 d after being pretested for 7 d. All pigs were free access to feed and water. After the completion of feeding trial, 12 pigs from 200 μg/kg Cr from CrNano and CrCl3.6H20 treated group were randomly picked out to be slaughted to determine the carcass characteristics and meat quality and to collect samples for assay. Four selected skeletal muscles were dissected from the left carcass and weighted. Samples of blood, longissimus muscle, subcutaneous fat, liver, kidney, pancreas and heart were collected and stored in frozen state. Concentrations of Cr in blood , selected organs and LD samples were determined. Activities of fatty acid synthase, lipogenic enzymes and hormone sensitive lipase (HSL) in subcutaneous fat were analyzed. Concentrations of Glu, HDL, FFA, Ca, P, TP, SUN,TG3,CHL and activities of LIP, ALP, GOT, GPT in serum. RIA was used to determine the concentrations of TSH, T3, T4, GH, Insulin, IGF-1 in serum samples.In addition, contents of nucleic acid, intramuscular fat and myoglobin in Longissimus muscle were determined.It is found that all the forms of Cr have good solubility in pH 8.5 solution. And solubility of CrNano is 28. 98%, 23. 56%, 46. 71%, 20. 82%, 18. 13% less than CrCl3 when 100,200,400,800,1600 ppb Cr solutions were adjusted to pH 8.5.The results from feed trial indicated that ADG of pigs was increased by 3.34% (P>0.05), F/G ration was decreased by 2.99% (P<0.05) when 200 g/kg CrNano was added. No significant difference was found in ADFI. ADG of pigs supplemented with 200u/kg CrNano was increased by 5.59% (P>0.05), F/G ration was decreased by 3.56% (PO.05) comparing to same level Cr from CrCls added group.Determination of carcass showed that Nanoparticulate Cr significantly improved carcass characteristics of finishing pigs. Group fed 200|ig/kg CrNano diets had 7.10 percentage higher dissected lean (P<0.05); 20.22% largerer longsissimus muscle area (p<0.05); 26.57%(p<0.05) lower fat percentage and 15.93%(p<0.05) thinner 10th rib backfat respectively. Sex difference was found in the effect of CrNano on improving carcass composition, gilts had better responses to CrNano than barrow. In addition, weights of longissimus muscle and semimembranosus were increased by 16.33% (PO.05), 14.87% (P<0.05) respectively with the supplementation of CrNano.It was found that 24-h drip loss was decreased by 21.48%(P<0.05) and content of myoglobin was increased by 72.69% by adding CrNano in the diet.Analysis of Cr content in blood, muscle and selected organs showed that Cr concentration in longissinus muscle was greatly elevated by 184.00%(P<0.05), and that Cr contents in blood, liver, pancreas, kidney and heart were increased by 144.99% (PO.05), 140.50% (PO.05) , 88.13% (PO.05) and 52.60% (PO.05) respectively.The subcutaneous fat (10th rib ) was used to analyse the fat acid synthase (FAS), lipogenic enzyme activities and hormone sensitive lipase (HSL).It was found that the activities of FAS, isocitrie dehydrogenase (ISD) and malic dehydrogenase (MDH) were significantly decreased in CrNano treated group. Comparing to Cr from CrCl3.6H20 group,200 ng/kg CrNano added increased activity of FAS by 40.74% (PO.05). Total and relative activities of ISD and MDH were decreased by 72. 56% (P<0. 05), 80. 45% (P<0. 05)...
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