氨基酸锌及氨基酸锌、铜、锰复合对育成期蛋鸡生长性能及组织抗氧化机能的影响

试验选择 5 76只 3周龄海兰褐壳蛋鸡 ,研究日粮添加氨基酸锌以及氨基酸锌、铜、锰复合添加对育成期蛋鸡生产性能及抗氧化机能的影响。试验结果表明 ,与不加锌的对照组相比 ,添加氨基酸锌及复合添加氨基酸锌、铜、锰提高 3～ 8周龄的采食量。与ZnSO4相比 ,氨基酸锌显著 (P <0 .0 5 )提高 8周龄时肝脏T SOD和CuZnSOD的活性和总抗氧化力 (TAOC) ,降低 18周龄时肝脏丙二醛 (MDA)的含量 ;显著 (P <0 .0 5 )提高脾脏 8周龄TAOC和 18周龄时的CuZn SOD、T SOD的活性 ,显著降低 (P <0 .0 5 ) 8周龄和 18周龄时脾脏MDA的产量。日粮添加微量元素Zn ,Cu ,Mn氨基酸络合物组合与相同水平的无机盐相比显著提高蛋鸡 18周龄肝脏TAOC ,8周龄脾脏TAOC以及 18周龄脾脏GSH Px的活性 ;显著降低 18周龄肝脏MDA含量和 8周龄脾脏MDA的含量 (P <0 .0 5 )。而相同来源不同水平的微量元素组合除 18周龄肝脏TAOC值因元素供给量增大而提高外 ,其它指标均没有显著差异     

富锗酵母菌培养物对蛋鸡抗氧化性能及血清生化免疫指标的影响

本试验旨在探究富锗酵母菌培养物对产蛋高峰期的海兰褐壳蛋鸡抗氧化性能、血清生化指标和免疫指标的影响。试验将240只健康无病、日龄及体况较一致的海兰褐壳蛋鸡随机分为对照组和试验组,每组120只,各12个重复,每个重复10只。其中试验组日粮中添加0.2%富锗酵母菌培养物,对照组饲喂基础日粮;预饲期7 d,正式试验42 d。结果显示:与对照组相比,试验组血清中总胆固醇含量降低了17.24%(P0.05);甘油三酯含量降低了19.73%(P0.05);尿素氮含量降低了22.68%(P0.05);IgG含量提高了5.39%(P0.05);SOD活性提高了12.18%(P0.01);MDA活性降低了10.06%(P0.05);蛋鸡肝脏中SOD、GSH-Px活性分别提高了21.46%(P0.01)和11.16%(P0.05);蛋黄中MDA活性降低了17.78%(P0.01)。试验表明:日粮中添加0.2%富锗酵母菌培养物可显著提高蛋鸡抗氧化性能及免疫性能。     

低蛋白日粮添加必需氨基酸对肉鸡血清抗氧化指标和肝脏抗氧化性能的影响

研究旨在探讨低蛋白日粮中添加必需氨基酸对肉鸡血清抗氧化指标和肝脏抗氧化性能的影响。选用200只1日龄AA~+白羽雄性商品肉鸡,随机分为4个处理组,每个处理组设置5个重复,每个重复10只。对照组饲喂按照NRC(1994)标准推荐的基础日粮,试验组分别在对照组基础上饲喂降低3%粗蛋白水平的日粮,前期各试验组肉鸡饲喂分别添加0.1%DL-蛋氨酸(DLM)、0.22%L-赖氨酸(Lys)和0.1%DLM+0.22%Lys的日粮,后期各试验组肉鸡饲喂分别添加0.1%DLM、0.26%Lys和0.1%DLM+0.26%Lys的日粮。试验分为生长期(1~21日龄)和育肥期(22~42日龄)两个阶段,共42 d。结果表明:低蛋白日粮中添加必需氨基酸极显著提高21日龄肉鸡肝脏谷胱甘肽过氧化物酶(GSH-Px)活性、血清及肝脏总抗氧化能力(T-AOC)(P0.01),显著提高血清中超氧化物歧化酶(SOD)活性(P=0.05),极显著或显著降低血清及肝脏中丙二醛(MDA)和抑制羟自由基(·OH)含量(P0.01,P0.05);显著提高42日龄肉鸡肝脏中GSH-Px和T-AOC含量(P0.05),极显著提高血清及肝脏中SOD活性、肝脏中T-AOC含量(P0.01),极显著降低血清及肝脏中MDA含量(P0.01)。提示低蛋白日粮添加必需氨基酸能够显著提高肉鸡的抗氧化性能,前期必需氨基酸添加水平为0.1%DLM+0.22%Lys,后期必需氨基酸添加水平为0.1%DLM+0.26%Lys时抗氧化性能最高。     

大豆黄酮对奶牛血清抗氧化能力和免疫功能的影响

40头健康中国荷斯坦奶牛按胎次、产奶量、泌乳期相近的原则随机分成4组(n=10),试验组日粮中分别添加45、60、70mg/kg的大豆黄酮,对照组饲喂基础日粮。在试验前及试验后10、30、60d颈静脉采血,测定4组奶牛血清中SOD、GSH-Px、CAT活性,MDA含量、T淋巴细胞转化率和T细胞数,探讨大豆黄酮对奶牛血清抗氧化能力和免疫功能的影响。结果表明,与对照组相比较,试验组GSH-Px、CAT和SOD活性显著或极显著升高(P<0.05或P<0.01);MDA含量明显低于饲喂大豆黄酮前(P<0.01);大豆黄酮60、70mg/kg添加组淋巴细胞转化率和T细胞数显著高于对照组(P<0.05)。     

高能低蛋白日粮致脂肪肝出血综合征鸡抗氧化能力和肝损伤的研究

选用140日龄健康海兰褐壳蛋鸡102只,随机分为对照组(饲喂日粮代谢能与粗蛋白分别为11.51MJ/kg、15.58%)和试验组(饲喂日粮代谢能与粗蛋白分别为14.47MJ/kg、12.55%),每组设3个重复,每个重复17只。于试验期第15、25、35、45、55天,每组取6只鸡测定其血清和肝脏中超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)活性和丙二醛(MDA)含量,同时对肝脏作病理组织学检查。结果显示:(1)试验组蛋鸡表现肝脂蓄积,肝脂肪变性,出现典型脂肪肝出血综合征病变,证明高能低蛋白日粮可以成功复制蛋鸡脂肪脏出血综合征。(2)与对照组相比,试验组血清和肝脏匀浆中MDA含量升高,抗氧化酶SOD、GSH-Px、CAT活力最终都降低,表明机体抗氧化能力下降。结果表明,自由基在高能低蛋白日粮致脂肪肝出血综合征的发生、发展过程中起重要作用。     

日粮中添加大豆黄酮对鹌鹑生产性能和血液中激素水平的影响

本试验采用了 3个生产阶段的蛋用鹌鹑。 35日龄开产期蛋用鹌鹑日粮中添加 3mg/kg大豆黄酮 ,鹌鹑的产蛋率和血液中T3 水平均发生显著性提高 (P <0 0 5 )。 7月龄蛋用鹌鹑日粮中添加 3mg/kg大豆黄酮 ,可显著提高鹌鹑的产蛋率 (P <0 0 5 )和血液中T3 水平 (P <0 0 5 ) ;而日粮中添加 6mg/kg大豆黄酮则使鹌鹑的产蛋率显著下降 (P <0 0 5 )。 12月龄蛋用鹌鹑日粮中添加 6mg/kg大豆黄酮 ,鹌鹑的产蛋率提高 10 3% (P <0 0 1) ;血液中T3 、T4和IGF 1水平分别提高 34 8% (P <0 0 1)、2 7 6 % (P <0 0 5 )和 30 8% (P <0 0 5 )。本次研究结果表明 ,日粮中添加一定剂量大豆黄酮能显著增加开产期、高峰期和后期蛋用鹌鹑的产蛋率 ,并影响其内分泌机能     

中药负离子硒锗复合生物制剂对蛋鸡生理机能、免疫抗氧化性能的影响

试验旨在探究中药负离子硒锗复合生物制剂对蛋鸡生理机能和免疫抗氧化性能的影响。选取200只28周龄的健康海兰褐蛋鸡,随机分成2组,对照组饲喂基础日粮,试验组饲喂基础日粮+0.5%中药负离子硒锗复合生物制剂,每组4个重复,每个重复25只鸡,试验期共49 d。结果表明:与对照组相比,试验组血清白蛋白(ALB)和白蛋白/球蛋白(ALB/GLO)分别显著升高了8.33%、11.11%(P0.05);试验组血清总胆固醇(TC)含量显著降低8.68%(P0.05),高密度脂蛋白(HDL)含量显著升高8.24%(P0.05);试验组血清谷草转氨酶(GOT)和谷丙转氨酶(GPT)活性差异不显著(P0.05);试验组血清Ig G含量显著升高4.89%(P0.05);试验组血清超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)活性分别极显著升高23.49%、17.82%(P0.01),血清丙二醛(MDA)含量极显著降低32.08%(P0.01)。综上,蛋鸡基础日粮中添加0.5%中药负离子硒锗复合生物制剂可改善蛋鸡生理机能,提高蛋鸡免疫力和抗氧化性能,且对蛋鸡肝脏无不良影响。     

八角油对育肥猪抗氧化能力的影响

为了研究八角油对育肥猪抗氧化能力的影响,试验选用体重相近([83.8±1.27)kg]的育肥猪(杜×长×大)商品猪16头,随机分为2个处理,每个处理8头。对照组饲喂基础日粮;试验组在对照组的基础上添加0.02%的八角油。预试期7 d,正式期35 d,结果表明:试验组育肥猪血清(P=0.011)和肝脏(P=0.003)中SOD(超氧化物歧化酶)的活性显著高于对照组,而肌肉中MDA(丙二醛)的含量显著低于对照组(P=0.002)。饲喂0.02%的八角油可使育肥猪血清和肝脏中SOD活性分别提高7.7%和18.6%;肌肉中MDA含量降低16.0%。八角油能够改善育肥猪抗氧化能力。     

混合型啤酒酵母粉对产蛋后期蛋鸡生产性能、 蛋品质和抗氧化的影响

试验旨在研究日粮中添加混合型啤酒酵母粉对产蛋后期蛋鸡生产性能、蛋品质和抗氧化的影响。试验选择60周龄海蓝褐蛋鸡6 000只,随机分成2个处理,每个处理5个重复,每个重复600只。对照组饲喂基础日粮,试验组在基础日粮中添加1.5 g/kg的混合型啤酒酵母粉。预试期3周,试验期8周。研究结果表明:①与对照组相比,日粮中添加混合型啤酒酵母粉显著提高了8 wk和5～8 wk蛋鸡的产蛋率和产蛋量(P<0.05),有提高4 wk蛋鸡产蛋量的趋势(P=0.083),显著降低了4、8、5～8 wk料蛋比和8 wk蛋鸡采食量(P<0.05),显著提高了5～8 wk和1～8 wk蛋鸡的合格蛋率(P<0.05)。②与对照组相比,日粮中添加混合型啤酒酵母粉显著提高了蛋鸡蛋白高度(P<0.05),有提高蛋壳强度的趋势(P=0.083),对蛋壳厚度、蛋黄颜色、哈氏单位、蛋黄比例、蛋清比例、蛋壳比例没有显著影响(P>0.05)。③与对照组相比,日粮中添加混合型啤酒酵母粉显著降低了蛋鸡肝脏和蛋黄MDA含量(P<0.05),显著提高了蛋黄SOD活性(P<0.05),对肝脏SOD活性没有显著影响(P>0.05)。综上所述,日粮中添加混合型啤酒酵母粉能够改善蛋鸡的产蛋性能、饲料效率、蛋品质和抗氧化性能。     

蛋鸡日粮中添加植物油对肝脏和鸡肉中 C-18系列脂肪酸含量的影响

将 60只 5 2周龄蛋鸡分为三组 ,对照组饲喂基础日粮 ,两试验组分别饲喂含 3 %的大豆油和 3 %的花生油日粮 ,研究日粮中添加植物油对肝脏和胸肌中C 18系列脂肪酸的影响 ,结果表明 :日粮中添加 3 %植物油可明显提高生产性能。肝脏中硬脂酸、油酸、亚油酸和亚麻酸的含量以及胸肌中硬脂酸、亚油酸和亚麻酸的含量明显高于对照组 (P <0 0 5 )。试验 1组肝脏和胸肌中亚油酸和亚麻酸的含量与试验 2组差异显著 (P <0 0 5 )。     

Effect of dietary supplementation of organic zinc on laying performance,egg quality and some biochemical parameters of laying hens

This study was conducted to evaluate the effects of zinc methionine (Zn‐Met) supplementation on the performance, egg quality, antioxidant status and some biochemical parameters of blood serum in laying hens from 22 to 34 weeks of age. A total of 120 Hisex Brown laying hens of 22‐week‐old were randomly allocated into five treatments with six cage replicates for each (four hens/replicate). Dietary treatments consisted of the basal diet with no Zn‐Met supplementation (control group) and basal diet supplemented with 25, 50, 75 or 100 mg Zn‐Met/kg diet. No significant differences were observed on body weight, body weight gain or feed conversion ratio due to dietary Zn‐Met supplementation. However, highly significant impact was observed on daily feed intake. Egg number, egg weight and egg mass were increased in the group fed diet supplemented with the highest level of Zn‐Met (100 mg/kg of diet) as compared to other groups. All egg quality traits were statistically (p > .05 or .01) affected as a response to dietary Zn‐Met supplementation except egg shape index, shell percentage and yolk index. In comparison with the control group, dietary supplementation of 25, 50, 75 or 100 mg Zn‐Met/kg decreased serum triglyceride and LDL‐cholesterol levels. Serum cholesterol level was increased with all dietary levels of Zn‐Met in comparison with the control group. Dietary Zn‐Met supplementation increased the serum content of zinc, where the highest values were recorded with 50 and 100 mg Zn‐Met/kg diet. Dietary Zn‐Met levels did not affect the antioxidant indices in blood serum except for the activity of copper–zinc superoxide dismutase (Cu‐Zn‐SOD). The activity of Cu‐Zn‐SOD was increased with Zn‐Met supplementations with no differences among supplemental zinc levels. It is concluded that dietary Zn‐Met supplementation reduced serum triglyceride, LDL‐cholesterol and increased Zn status and resulted in promoting antioxidant ability of laying hens, and the addition of 100 mg Zn‐Met/kg to layer diet was appropriate for improving the above parameters in addition to egg production indices and Haugh unit score.     

女贞子、五味子、四君子汤、大豆黄酮和黄霉素对蛋鸡脂质稳定性的影响

试验选用51周龄海兰褐蛋鸡144只,随机分为6个处理组,试验1、2和3组分别添加1%的女贞子、五味子和四君子汤,试验4组添加10mg/kg的大豆黄酮,试验5组添加5mg/kg黄霉素,试验6组为对照组。研究中草药及大豆黄酮对蛋鸡脂质稳定性的影响及其机理,同时比较中草药、大豆黄酮和黄霉素的效果。设预试期1周,正试期为6周。结果表明:1)添加3种中草药和大豆黄酮均有降低蛋鸡组织、血清或蛋黄中脂质过氧化物含量的作用,其中3种中草药的作用明显优于大豆黄酮和黄霉素(P<0.05),黄霉素的作用不明显;2)中草药、大豆黄酮和黄霉素对超氧化物歧化酶活性没有显著提高(P>0.05),但能显著提高谷胱甘肽还原酶活性(P<0.05);3)3种中草药和大豆黄酮均可显著提高蛋鸡组织或血清中谷胱甘肽含量(P<0.05)。结论为:3种中草药和大豆黄酮均有增强蛋鸡抗氧化水平和脂质稳定性的作用;3种中草药的抗氧化作用优于大豆黄酮;黄霉素对蛋鸡的抗氧化机能没有影响。     

日粮中长期添加大豆黄酮对产蛋鸡产蛋性能及有关内分泌的影响

试验旨在探讨日粮中长期添加大豆黄酮对产蛋高峰期蛋鸡采食和生产性能的影响及有关内分泌机制。40羽180日龄产蛋鸡,均分为2组,对照组饲喂基础日粮,试验组饲喂基础日粮+大豆黄酮(6mg/kg),试验期为150d。结果显示:试验组蛋鸡采食量、产蛋率、只日蛋重、每枚蛋重均显著提高,料蛋比显著下降;血清17β-雌二醇、T3、T4水平均显著提高,而血清瘦素(leptin)水平有下降的趋势。试验结果表明,大豆黄酮可调控血液激素水平而提高产蛋鸡生产性能,并使产蛋高峰期得到延长。     

饲料中镉含量对蛋鸡生产性能及抗氧化功能的影响

为研究日粮中低剂量镉对蛋鸡生产性能和血清、肝肾抗氧化能力的影响,将192羽巴布考克B300蛋鸡随机分为4组,每组3个重复。对照组饲喂玉米-豆粕型基础日粮,试验组日粮为在基础日粮中分别添加5、10、20 mg/kg的镉(氯化镉形式,CdCl2.2.5H2O),试验期9周。结果表明:在1～3、4～6、7～9周,试验组的产蛋率、日采食量均低于对照组(P>0.05);各组在第7～9周时的采食量显著低于1～3周(P<0.05);血清中GSH-Px、GST、GR酶活力对镉不敏感(P>0.05),随镉添加量升高肝肾中GSH-Px活力先升后降,试验组肝肾中总巯基含量较对照组有显著升高(P<0.05);血清和肝肾中总SOD、CuZn-SOD、CAT活力随镉添加量升高呈先升后降的趋势;血清和肝肾中MDA、NO含量随着镉添加量的升高显著升高(P<0.05),总抗氧化能力均呈下降趋势。试验结果证实,镉可引起产蛋鸡体内抗氧化功能受损,机体产生氧化应激,并可能由此导致蛋鸡的生产性能下降。     

Effects of dietary L-threonine levels on antioxidant capacity,digestive enzyme activities,and antibody production of Xinyang green-shell laying hens

Xinyang green-shell laying hens (n = 720), 32 wk of age were allocated to 5 dietary treatments groups, each of which included 6 replicates of 24 hens. The control group was given a basal corn-peanut-soybean meal diet containing 0.47% L-threonine (L-Thr). L-Thr levels of the experimental groups were 0.57, 0.67, 0.77, and 0.87%, respectively. The trial lasted 10 wk. Serum concentrations of total superoxide dismutases (T-SOD) and superoxide dismutases (SOD) were maximized at 0.67% L-Thr group. The 0.57% L-Thr group had the highest serum total antioxidative capacity (T-AOC), while the 0.67% L-Thr group had the lowest serum malondialdehyde (MDA) concentration. Hens fed 0.67% L-Thr of the diet resulted in the highest SOD and T-AOC levels in the liver. The activity of amylase and lipase in the jejunum was maximized at 0.77% L-Thr level. Hens fed 0.77% L-Thr in the diet resulted in the highest IgM and IgG levels in the jejunum. In conclusion, we suggest that a L-Thr level above 0.67% may have had an antioxidant capacity and positive effect on digestive enzyme activities and antibody production in the jejunum of Xinyang green-shell laying hens.     

添喂大豆黄酮对自由采食蛋鸡生产性能的影响

选用 40羽 1 3周龄伊莎蛋鸡 ,随机分为 2组 ,对照组饲喂基础日粮 ,大豆黄酮 (Da)组饲喂基础日粮添加Da 6mg/kg。结果显示 :添加Da组青年期母鸡摄食量增加 7 2 9% (P <0 0 5) ,产蛋初期母鸡摄食量增加 4 32 % ,产蛋率增加 31 0 6 % (P <0 0 1 ) ,每只日蛋重增加 45 78% (P <0 0 1 ) ,料蛋比下降 2 9 88% (P <0 0 1 ) ,产蛋高峰期母鸡摄食量增加 7 95 % (P <0 0 1 ) ,产蛋率增加 1 0 72 % (P <0 0 5) ,每只日蛋重增加2 0 0 9% (P <0 0 5) ,料蛋比下降 1 2 81 % (P <0 0 5)。与各自的对照组相比较 ,三期血清LH水平分别升高 0 57% ,2 2 84% (P <0 0 5)及2 5 96 % (P <0 0 5) ,胰岛素水平分别升高 1 3 1 1 % ,1 4 54 % (P <0 0 5)和 1 2 85% (P <0 0 5) ,瘦素水平升高 6 2 0 % ,2 3 72 % (P <0 0 5)和9 32 % ,雌二醇水平升高 38 1 6 % (P <0 0 1 ) ,1 5%和 1 3 96 %。提示大豆黄酮能够改善蛋鸡生产性能 ,并对相关内分泌产生影响     

Polyphenols in Eucalyptus leaves improved the egg and meat qualities and protected against ethanol‐induced oxidative damage in laying hens

Polyphenols in Eucalyptus leaves (PE) were value resources due to various pharmacological activities, but data on the effect on laying hens are very scare. This study was conducted to determine the effect of PE on the laying performance, egg traits, meat quality, antioxidant status and liver tissues of laying hens. One hundred and twenty 256‐day‐old Yueqinhuang laying hens were randomly assigned to four treatment groups (different levels of PE at 0, 0.5, 0.8 and 1.2 g/kg diet) for 63 days with 15 replicates per group. Addition of 0.8 g/kg PE not only improved the egg trait by increasing the eggshell thickness and decreasing MDA production and cholesterol content in the egg yolk, but also significantly enhanced meat quality of hens, as suggested by the increase pH_45 min (p < .01) and a* value, and decrease drip loss rate (p < .01). Meanwhile, under acute ethanol‐induced oxidative damage condition, supplementation of 0.8 g/kg PE enhanced the serum antioxidant status by increasing enzymatic activities (GSH‐PX, T‐SOD, T‐AOC), inhibited oxidative damage and provided protective effect to liver tissue. In conclusion, addition of 0.8 g/kg PE not only improved the egg traits and meat quality without obvious adverse effects, but also increased the serum antioxidant status of the hens and protected their liver tissue from ethanol‐induced oxidative damage. This study indicated that PE could be utilized as an effective feed additive for laying hens to improve health performance and egg traits.     

大豆黄酮对伊莎鸡卵泡发育及其P450arom基因表达的影响

实验探讨了大豆黄酮(DAI)对伊莎鸡卵泡发育及其芳香化酶(P450arom)mRNA表达的影响。实验选取16只产蛋后期伊莎鸡,等分为对照组和DAI处理组。对照组饲喂基础日粮,实验组在基础日粮中添加10 mg/kgDAI。实验持续7周后,分离排卵前卵泡(F1、F2、F3……)的颗粒层及小黄卵泡和大白卵泡,通过RT-PCR法检测P450arom mRNA表达的相对丰度。结果表明:DAI明显提高了伊莎鸡小黄卵泡和大白卵泡的数量,P450arommRNA在伊莎鸡不同发育阶段卵泡中的表达存在差异,部分卵泡P450arom mRNA表达的相对丰度显著增加。因此,在产蛋后期伊莎鸡基础日粮中添加DAI可增加不同发育阶段卵泡的数目,上调部分卵泡中与发育相关的基因表达以促进卵泡发育。     

Tea polyphenols increase the antioxidant status of laying hens fed diets with different levels of ageing corn

This study was conducted to evaluate the effects of ageing corn levels (stored for 4 years) with or without the supplementation of tea polyphenols (TPP) on the performance, egg quality and antioxidant status of laying hens. A total of 288 Lohmann commercial laying hens (63-week-old) were used under a 2 × 4 factorial arrangement with 4 levels of dietary ageing corn (0%, 25%, 50%, or 100%) and 2 levels of TPP (0 and 600 mg/kg) for 8 wk. Dietary ageing corn linearly decreased (P < 0.05) the egg production, serum total antioxidant capacity (T-AOC), liver glutathione peroxidase (GSH-Px) of laying hens, yolk index, yolk colour, 1,1-diphenyl-2-picrylhydrazyl (DPPH) value and the reducing power value of egg yolk, but it linearly increased (P < 0.05) the feed conversion rate, ovary malondialdehyde (MDA) content of laying hens, and the protein carbonyl content of egg yolk. Tea polyphenol supplementation increased (P < 0.05) the serum T-AOC, serum superoxide dismutase (SOD), liver SOD, liver GSH-Px, ovary SOD, GSH-Px, the expression of antioxidant-related genes of laying hens, albumen height, Haugh unit, DPPH value and the majority free amino acids of egg yolk, but it decreased (P < 0.05) the serum MDA content of laying hens, MDA and protein carbonyl of egg yolk. In conclusion, the ageing corn significantly reduced the performance, egg quality, antioxidant status and egg antioxidant capacity of laying hens, while TPP supplementation partially counteracted the adverse effects, especially antioxidant status and egg antioxidant capacity of laying hens.     

Ascorbic acid synthesis and transportation capacity in old laying hens and the effects of dietary supplementation with ascorbic acid

Background: Laying hens over 75 weeks of age commonly show great declines in immunity and production performance.It is unclear whether these declines can be relieved by supplementing with ascorbic acid(AA) in feed.Two trials were conducted to investigate the synthesis and metabolism of AA in layers of different ages and the effects of dietary supplemental AA on the performance and the immune and antioxidant statuses of 78 weeks old hens.Methods: In Exp.1,equal numbers(24 hens) of 35 weeks old(Young) and 75 weeks old(Old) layers were fed the same diet without AA supplementation for 4 weeks.In Exp.2,360 healthy 78 weeks old laying hens were randomly assigned to 4 treatments(basal diet supplemented with 0,0.25,0.5,or 1 g AA/kg diet) in an 8-week feeding trial.Results: The old hens tended to have decreased L-gulonolactone oxidase(GLO) synthase activity in the kidney and liver than that of the young hens(P = 0.07 and P = 0.05,respectively).Compared with the young hens,the old hens had lower hepatic antioxidant capacity allowing for the lower thioredoxin(TXN),thioredoxin reductase(TXNR) and cytochrome b5 reductase(CYB5 R) gene expression(P 0.05),whereas increased sodium-dependent vitamin C transporter(SVCT) 1 expression levels in the ileum and kidney and enhanced splenic and hepatic AA concentrations(P 0.05).Dietary supplementation with AA significantly decreased GLO enzyme activity but increased splenic AA concentration and anti-bovine serum albumin IgG levels(P 0.05) and tended to increase CD4+T lymphocyte numbers(P = 0.06) in serum.Supplementation of 0.25 g AA/kg diet significantly increased hepatic total antioxidant capacity(T-AOC,P 0.05) relative to the control group.Conclusions: Laying hens could synthesize AA in both the kidney and the liver,though the GLO enzyme activities were 100 times greater in kidneys than in livers.The old laying hens had greater absorption and reabsorption capacity and higher AA retention in some tissues that did the young hens.Dietary supplementation of AA can improve the health of old layers by enhancing immunity and antioxidant capacity.