Y affecting toughness of meat. Direct evidence of negative consequences of high doses of?2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Chen et al. Journal of Animal Science and Biotechnology (2016) 7:Page 2 ofisoflavones is still scarce in practical animal production. Accordingly, the objective of present study was to test the effects of dietary supplementation of high dose of the isoflavone daidzein on redox system in skeletal muscle, liver, and back fat and meat quality. The level of supplementation used here, 640 mg/kg feed, is 15 times higher than that providing optimal antioxidant function [4].Table 1 Composition PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/28506461 of the basal diet fed to finishing pigs (as-fed basis)Item Ingredient Corn Soybean Wheat middlings Monocalcium phosphate 68.7 22.1 6.0 0.7 1.0 0.4 0.aContentMethods The experimental protocol used in this study, including animal management, housing, and slaughter procedures, was approved by the Animal Care and Use Committee of Guangdong Academy of Agricultural Sciences.Animal and housingLimestone, ground Salt L-Lys.HCl Trace-mineral premix Vitamin premixb Calculated chemical composition DE, MJ/kg CP, Ca, P, total, P, available, Lys, Methinone, Met + Cys, Thr, Trp,a0.5 0.13.40 16.00 0.62 0.49 0.25 0.85 0.24 0.50 0.60 0.A total of 48 hybrid finishing pigs (Duroc ?Landrace ?Large White, 24 gilts and 24 barrows) averaging 57 kg BW were obtained from a single source (a purchase XR9576 commercial swine farm in South China) and transported to the trial farm. Pigs of each sex were initially blocked into 2 weight groups then randomly assigned to either treated or control groups, each consisting of 6 pens (2.5 m ?2.5 m), of 4 pigs (2 barrows and 2 gilts) of comparable total starting BW. Pigs in the control group were fed a basal diet that met the NRC [9] recommendation for finishing phase (Table 1). The treated pigs received the basal diet supplemented with 640 mg/kg daidzein, provided by Guangdong Newland Feed Science Technology Co., Ltd. Pigs were weighed after fasting for 12 h at the beginning and end of the 64-d finishing period to determine average daily gain (ADG). Feed and water were provided ad libitum throughout the entire experiment period. Average daily feed intake (ADFI) for pigs was calculated as feed offered minus feed refused every 7 d. Average daily gain: feed intake (G:F) was obtained based on ADG and ADFI. On d 64, heparinized blood (10 mL) was collected by jugular venipuncture from 1 gilt and 1 barrow in each pen, 4 h after feeding (1400 h). Blood was held on ice until centrifugation (3,000 ?g for 15 min at 4 ), aliquots of plasma were stored at -20 for subsequent analysis. The blood-sampled barrows (n = 6 in each treatment group) were then fasted for 12 h, with water available, weighed on d 65 and electrically stunned and exsanguinated. Back fat, abdominal fat, liver and longissimus muscle (6/7th lumbar vertebra level) were immediately sampled, snap-frozen in.