发酵豆渣对哺乳母猪生产性能的影响

为研究哺乳母猪饲料中添加发酵豆渣对哺乳母猪生产性能的影响,试验在江苏泰州一规模化猪场选取10头哺乳母猪进行发酵豆渣替代部分豆粕和麸皮饲养试验。结果表明,日粮添加5%的发酵豆渣提高了母猪泌乳期日均采食量;在哺乳期24 d时,发酵豆渣组仔猪存活率比对照组高32%;在哺乳期27 d时,发酵豆渣组仔猪平均体增重增加。母猪泌乳量和仔猪窝重在哺乳期24 d和27 d无显著差异。泌乳期日粮添加5%的发酵豆渣改善了饲料的适口性,增加了母猪采食量,提高了仔猪存活率,使母猪产后体况恢复良好。     

给哺乳母猪日粮添加脂肪对仔猪胴体成分的影响

内布拉斯加的S．L．Tilton等人做了2个试验。试验1，采用2组18只母猪评价添加脂肪对母猪及其仔猪生产性能和奶产量及其成分的影响。母猪不限量采食玉米豆粕型日粮(对照组)，或含10％牛羊油的相似日粮，结果处理间进食量、ME进食量和奶产量无差别(P＞0．10)。喂牛羊油母猪奶中由于脂肪和灰分含量增加(P＜0．05)，所以干物质百分率较高(P＜0．05)。与喂对照日粮母猪奶中脂肪酸百分率相比，喂牛羊油日粮母猪奶中C10∶0、C14∶0、C16∶1和C18∶3脂肪酸百分率较低(P＜0．05)，C18∶0和C18∶1脂肪酸百分率较高(P＜0．05)。试验2， 30只母猪喂与试验1中相似日粮，用于确定牛羊油日粮对断奶仔猪胴体成分的影响。一窝仔猪数标准化为10只仔猪。结果，母猪的酸性洗涤纤维进食量(ADFI)无差别(P＞0．10)。周2(P＜0．05)、周3(P＜0．05)和整个哺乳期(P＜0．05)，喂牛羊油母猪的ME进食量比喂对照组母猪的多。喂牛羊油日粮母猪的仔猪断奶窝重比对照组母猪的仔猪重(P＜0．05)。喂牛羊油母猪仔猪的胴体脂肪重和脂肪率较高(P＜0．05)、水分和蛋白质百分率较低(P＜0．05)。表明，喂牛羊油母猪奶中脂肪含量增加使得哺乳这些母猪的仔猪增重增加，增加的增重成分几乎仅是脂肪。     

生菌素、维吉尼霉素对哺乳仔猪生长和血清代谢物的影响

将90头平均体重4.98kg哺乳仔猪(杜×大×长)分成2组,日粮中分别添加维吉尼霉素(对照组)和生菌素(普乐宝)。结果表明,与对照组相比,试验组日增重、饲料转化率和血清球蛋白水平提高(P>0.05或P<0.05);仔猪腹泻率、血清尿素氮、血糖和胆固醇含量下降(P<0.05);仔猪每千克增重收益增加2.85%。     

葛叶粉饲喂长毛兔的试验效果

用6窝共63头哺乳仔猪,进行了5周的饲料酸化剂添加效果试验。试验设3个组,即乳香酸组(0.2%)、柠檬酸组(1.5%)及对照组。3组基础饲料组成一致,2周龄起试,7周龄结束试验。试验结果表明,饲料中添加酸化剂能提高哺乳仔猪日增重及改善饲料利用率。酸化剂对哺乳仔猪日增重的影响随着酸化剂的种类及仔猪的日龄而有所不同。复合酸化剂乳香酸比单一酸化剂柠檬酸效果好而稳定;酸化剂在仔猪4周龄前效果不明显,4—5周龄效果最好,乳香酸组日增重比对照组提高31.0个百分点(P＜0.05),柠檬酸组日增重比对照组提高24.1个百分点,6周龄以后效果减弱。本试验中,酸化剂对哺乳仔猪降低腹泻率及提高成活率的影响均主要发生在4周龄以后,且复合酸化剂的效果优于单一酸化剂。     

中草药添加剂银翘散和止泻散在养猪业中的应用研究

选择生产性能与胎次接近的临产母猪60头,随机分为2组,选择出生日期、断奶重、体型相近的断奶仔猪60头,随机分为试验组和对照组,每组30头。哺乳母猪在产前7d和产后8d、保育仔猪在断奶换料后30d、添加0.1%的银翘散和0.1%的止泻散,育成猪在转栏后30d,添加0.1%的银翘散,进行饲喂效果比较。结果表明,试验给与对照组21日龄断奶窝重差异极显著(P<0.01);窝日增重差异极显著(P<0.01);断奶个体重每头提高280g,差异极显著(P<0.01);平均断奶窝头数差异极显著(P<0.01);平均保育日增重每头提高14g差异显著(P<0.05);保育肉料比试验组为1∶1.51,比对照组减少0.08;育成结束重(81日龄个体重)差异极显著(P<0.01);平均育成日增重每头提高9g差异显著(P<0.05);育成肉料比试验组为1∶1.71,比对照组减少0.12。试验组的猪瘟、高致病性蓝耳病、伪狂犬、口蹄疫的免疫抗体合格率高于对照组;同时减少了哺乳期、保育期的发病率(P<0.05),降低了哺乳期的死亡率(P<0.01);节约了药费哺乳期每头2.33元(P<0.01),保育期2.27元(P<0.05),育成期2.12元。     

高海拔条件下锌硒对猪繁殖性能的影响

通过对基础妊娠母猪，生长发育后备公母猪及哺乳仔猪日粮添加不同剂量的锌、硒，经试验组和对照组比较，基础妊娠母猪的产仔能力有显著的提高，断奶后再发情率和受胎率提高，断奶及发情时间缩短。生长发育后备母猪初次发情时间提前，初情期体重明显增加，产仔性能显著提高。生长发育后备公猪采精时间提前，睾丸发育迅速，射精量、精子活率和精子数量显著提高，精子畸形率降低。哺乳仔猪抗病力增强，成活率和平均断奶个体重明显提高。实验结果表明，锌、硒对基础母猪，后备母猪的繁殖与生长发育及哺乳仔猪的生长发育均起着十分重要的促进作用。     

荣昌猪母猪钙、磷适宜需要量研究与应用

为研究荣昌猪妊娠母猪及哺乳母猪钙、磷适宜需要量,选择胎次相近的荣昌母猪,遗传来源相似,30头,采用不同钙磷水平纯合饲粮日粮饲喂荣昌母猪,测定荣昌母猪妊娠110d不同钙磷水平的血液指标,测定妊娠110d到哺乳21d母猪体重变化、仔猪初生窝重及21d时窝重变化规律。结果表明:在妊娠60d到妊娠110d的荣昌怀妊母猪饲喂处理2的钙磷水平为适宜水平(钙0.8磷0.65);荣昌母猪妊娠110d到泌乳21d时处理3日粮钙磷水平比较适宜水平(钙0.82磷0.66)。     

丁酸钠对断奶仔猪生长性能和小肠形态的影响

为研究丁酸钠对断奶仔猪生长性能和小肠形态的影响,本试验选用(21±1)日龄断奶、(6.62±0.03)kg健康“长×大”杂交仔猪36头,随机分为2个处理组,每个处理组3个重复(栏),每个重复6头仔猪,公母各半。试验日粮是在以玉米豆粕基础日粮基础上添加0.1%丁酸钠。试验期为21d。饲养结果表明,在断奶仔猪日粮中添加0.1%丁酸钠可显著降低断奶后1周的腹泻发生率(P<0.05),提高断奶仔猪7～21d的平均日增重(P<0.05),对采食量和料重比无显著性影响(P>0.05)。小肠组织形态观察结果表明,0.1%丁酸钠可显著提高断奶后第一周十二指肠和回肠绒毛高度与隐窝深度的比值和降低隐窝深度(P<0.05)。     

丁酸钠对断奶仔猪生长性能和小肠形态的影响

为研究丁酸钠对断奶仔猪生长性能和小肠形态的影响,本试验选用(21±1)日龄断奶、(6.62±0.03)kg健康"长×大"杂交仔猪36头,随机分为2个处理组,每个处理组3个重复(栏),每个重复6头仔猪,公母各半。试验日粮是在以玉米豆粕基础日粮基础上添加0.1%丁酸钠。试验期为21d。饲养结果表明,在断奶仔猪日粮中添加0.1%丁酸钠可显著降低断奶后1周的腹泻发生率(P<0.05),提高断奶仔猪7～21d的平均日增重(P<0.05),对采食量和料重比无显著性影响(P>0.05)。小肠组织形态观察结果表明,0.1%丁酸钠可显著提高断奶后第一周十二指肠和回肠绒毛高度与隐窝深度的比值和降低隐窝深度(P<0.05)。     

复合酶制剂对仔猪生长性能及饲料消化率的影响

目的 探究复合酶制剂对仔猪生长性能及饲料消化率的影响。方法 试验选用80头28日龄断奶仔猪，随机分为4组，即空白对照组、试验Ⅰ组、试验Ⅱ组和试验Ⅲ组，在基础日粮中根据体质量分别添加0、200、400、600 mg/kg的复合酶制剂，试验为期30 d。结果 与对照组相比，试验组Ⅱ和试验组Ⅲ仔猪的终测体重、平均日增重和平均日采食量显著升高(P<0.05),料重比显著降低(P<0.05)。与对照组相比，试验组Ⅱ和试验组Ⅲ仔猪对饲料中干物质、粗脂肪、粗蛋白、粗纤维和粗灰分的消化率显著升高(P<0.05)。结论 在基础日粮中添加复合酶制剂可以有效提高断奶仔猪的生长性能，改善仔猪对饲料中营养物质的消化，提高营养物质吸收率，且在该试验条件下，复合酶制剂的最适添加剂量为600 mg/kg。     

Effect of dietary iron levels on growth,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A 60‐day feeding trial was carried out to investigate the effect of iron on growth, body composition and digestive enzyme activities. Diets with seven levels of iron (53.9, 90.0, 115.6, 146.1, 176.0, 215.8 and 266.0 mg iron kg^?1 diet) were fed to Jian carp (initial weight 11.4 ± 0.0 g). Per cent weight gain (PWG), feed efficiency (FE) and protein efficiency ratio were the lowest in fish fed the basal diet (P < 0.05). Body protein content was increased with the increasing iron levels (P < 0.05), but moisture, lipid and ash of fish were not significantly affected by dietary iron levels (P > 0.05). Activities of trypsin, lipase, α‐amylase, Na⁺, K⁺‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase were improved with increasing dietary iron levels. Serum iron were significantly enhanced with dietary iron levels up to 146.1 mg iron kg^?1 diet, and plateaued. In conclusion, iron improved digestive enzyme activities of juvenile Jian carp and the dietary iron requirement for serum iron of juvenile Jian carp (11.4–64.0 g) was 147.4 mg iron kg^?1 diet with ferrous fumarate as the iron source.     

Growth, haematological parameters and tissue lipid peroxidation of soft-shelled turtles, Pelodiscus sinensis, fed diets supplemented with different levels of ferrous sulphate

Soft-shelled turtles, Pelodiscus sinensis , with an average weight of 5.55 g, were fed diets supplemented with eight levels of ferrous sulphate for 8 weeks. The analysed iron content ranged from 50.8 to 482.9 mg kg⁻¹. Growth rate of turtles fed the control diet with no iron supplementation was the lowest among all dietary groups. Haematological parameters including red blood cell, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration of the turtles fed the control diet were also significantly ( P  < 0.05) lower relative to the other groups. Thus, dietary iron at 50.8 mg kg⁻¹ (no supplemented iron) was deemed deficient for growth and ineffective at preventing anaemia in juvenile soft-shelled turtle. Whereas, a supplementation of 50 mg kg⁻¹ ferrous sulphate (a total dietary iron of 91.8 mg kg⁻¹) was enough to normalize the haematological values of soft-shelled turtles to the level similar to other iron supplement-fed groups. Within the tested dietary iron range, liver iron content curve-linearly ( r ² = 0.99) increased with increasing dietary iron level. Furthermore, thiobarbituric acid-reactive substances in liver tissues of the turtles have also increased when liver iron content increased. The dietary iron requirement of soft-shelled turtle is 120–198 mg kg⁻¹ when ferrous sulphate is used as the source of iron.     

膨化与非膨化饲料对大规格草鱼生长、体成分及部分生理生化指标影响

以商业配方为基础,配制膨化饲料和非膨化饲料饲喂初始体重（394.96±13.21g）草鱼（Ctenopharynodon idellus）120天,旨在对比这两种饲料对其生长、体成分及部分生理生化指标的影响。养殖试验在水库网箱（2m×2m×2m）中进行,每个处理组3个重复,每个重复30尾鱼。实验结果表明,与非膨化料组相比,膨化饲料组草鱼成活率和增重率显著提高（P＜0.05）,饵料系数显著降低（P＜0.05）,增重成本显著降低（P＜0.05）;肥满度、肝体比、脏体比和肠体比显著升高（P＜0.05）;鱼体血清血糖、甘油三酯、总固醇和过氧化氢酶显著升高（P＜0.05）;胰蛋白酶、淀粉酶和脂肪酶显著降低（P＜0.05）;肝脏谷丙转氨酶（GPT）显著升高,谷草转氨酶（GOT）显著降低（P＜0.05）;鱼体成分中水分和灰分无显著差异（P>0.05）,粗脂肪显著升高、粗蛋白显著降低（P＜0.05）。综上所述,与非膨化饲料相比,饲喂膨化饲料可使大规格草鱼生长性能和养殖效益提高,但会鱼体肥满度和粗脂肪含量提高。     

Growth and Mineral Absorption by Striped Bass Morone saxatilis Fed a Plant Feedstuff Based Diet Supplemented with Phytase

Two experiments were conducted to determine the effects of phytase on growth, apparent phosphorus (P), calcium (Ca), iron (Fe), zinc (Zn), magnesium (Mg), and copper (Cu) absorption, and apparent protein digestibility by striped bass Morone saxatills fed a high phytate diet. In experiment one, four diets with graded levels of phytase supplementation, 0, 500, 1,000, and 2,000 phytase units/kg of diet (PUkg), and a diet supplemented with inorganic P (positive control, total P, 0.73%; phytin P, 0.35%) were assigned to duplicate tanks, and were fed to fingerling striped bass for 16 wk. A digestibility trial was conducted at weeks 16–18, using 0.5% Cr₂O₃ as an indigestible marker in the diets. Phytase was sprayed post-extrusion on the basal diet (P-total, 0.58%; P-phytin, 0.35%). Experiment two consisted of a 2-wk digestibility trial with three treatments: 0 (basal; total P, 0.73%; phytin P, 0.34%), 1,000, and 2,000 PU/kg, assigned to four, three and three replicate tanks respectively. Each tank contained an average of 20 striped bass (mean weight: 400 9). The diet used was similar to the basal in experiment one, which was modified to have low essential trace mineral concentrations, in order to increase the sensitivity of the assay. In experiment one, significant improvements (P≤ 0.05) in growth, feed conversion ratios, and vertebral and scale ash concentrations of fish at the end of the experiment were achieved with either added inorganic P or increasing phytase supplementations. Results from both digestibility trials indicated that P absorption was improved with the addition of at least 500 PUkg. Absorptions of Ca and Fe were significantly increased (P≤ 0.05) and Zn absorption marginally improved (P≤ 0.06) when at least 2,000 PU/kg was supplemented to the diet. Protein digestibility, Mg and Cu absorption were not significantly different in any treatment. Whole carcass P retention was significantly improved with the addition of 1,000 PU/kg, and 2,000 PU/kg, when compared to fish fed the basal diet, 500 PU/kg and positive control treatments. Results from these experiments indicate that phytase supplementation of at least 1,000 PU/kg is adequate to maintain growth rate and health comparable to an inorganic P supplemented diet. In addition, bioavailability and utilization of P is increased with increasing phytase supplementation. Diet supplementation of 2,000 PU/kg increased Ca, Fe, and Zn digestibility by striped bass fed a high phytate diet.     

Use of cottonseed meal supplemented with iron for detoxification of gossypol as a total replacement of fish meal in Nile tilapia, Oreochromis niloticus (L.) diets

The objective of this study was to determine the effect of total replacement of fish meal by cottonseed meal (CSM) supplemented with various levels of iron in practical diets on growth performance, feed utilization, body composition and some biological and haematological parameters of Nile tilapia, Oreochromis niloticus (L.). Juvenile fish (average weight 3.78±0.1 g) were stocked in 18 glass aquariums (80 L each) at 25 fish per aquarium. Fish meal (50% of the diet) was used as the sole source of animal protein in the control diet 1. Diets 2–6 had 100% CSM (0.145% free gossypol) protein with various levels of supplemented iron (86, 486, 972, 1458 and 1944 mg Fe kg diet^?1) in diets 2–6 respectively. Diets were fed to fish twice daily at a rate of 3% of body weight during the first 12 weeks then 2% of the total fish biomass daily until the end of the experiment (30 weeks). The results of this study revealed that, groups of fish fed diets 1, 4, 5 and 6 had significantly (P≤0.01) the higher average body weight and specific growth rate than those of fish fed diet 2 (100% CSM without iron supplementation) and diet 3 (100% CSM plus 486 mg Fe kg diet^?1). The best values for feed conversion ratio, protein efficiency ratio and condition factor (K) were recorded with groups of fish fed diet 4 (100% CSM plus 972 mg Fe kg diet^?1). Red blood cell count, haematocrit and haemoglobin were increased with increasing levels of iron and significantly affected by dietary iron. Hepatosomatic index for diets 3–6 were not significantly different (P>0.05) and superior to that of diet 1 control [100% fish meal (FM)]. The gonadosomatic index of males of Nile tilapia was not influenced by CSM diets with or without iron, while females of Nile tilapia were significantly influenced with iron and the lowest values were recorded with groups of fish fed diet 2 (100% CSM without iron supplementation). Apparent digestibility coefficients of protein, fat dry matter and energy were relatively high for most diets supplemented with iron and increased by increasing iron supplementation. There were no significant differences between groups of fish fed diet 1 (100% FM) and diets 5 and 6 which contained 100% CSM with additional 1458 and 1944 mg Fe kg diet supplemental iron^?1 respectively. Proximate composition of whole body was not influenced by diet. Adding 972 mg Fe kg diet^?1 from ferrous sulphate to the CSM‐based diets that contained 972 mg free gossypol (1:1 iron to free gossypol ratio) for Nile tilapia reduce the negative effects of gossypol and improved growth performance, feed utilization and blood parameters and can totally replace fish meal in tilapia diets.     

饲料中铁元素含量对鱼菜共生系统水质及鱼菜生长的影响

通过控制饲料中铁元素含量,研究其对鱼(金鲫)、菜(红皱生菜和红油阿拉斯)生长和系统水质的影响。实验设置1个对照组和5个处理组,饲料铁含量分别为0、0、10、20、40和80 mg/kg。结果显示:该系统对水体质量有净化作用;不同铁含量对金鲫存活率影响不显著(P0.05),对增重率影响显著(P0.05);当饲料中铁含量为20 mg/kg时,金鲫鱼存活率和鱼体增重率均达到最大值;饲料中铁含量为80 mg/kg时,金鲫的存活率和增重率均出现下降趋势;饲料中不同铁含量对两种蔬菜的存活率和增重率均没有产生显著影响(P0.05),但在增重率方面有一定的差异。研究表明:饲料中添加铁元素能够促进金鲫和蔬菜的生长,当铁元素含量为20 mg/kg时,该鱼菜共生系统具有最佳的生产力。     

饲料中不同种类的碳水化合物对大菱鲆生长性能和代谢反应的影响

为探讨在低蛋白水平(40%)下,饲料中不同种类的碳水化合物(葡萄糖、蔗糖和糊精)对大菱鲆幼鱼[(8.12±0.04)g]生长、成活、饲料利用、体组成和血液生理生化指标等的影响,实验在对照组饲料中未添加可消化碳水化合物,含40%的蛋白质和18%的脂肪,然后在对照组饲料的基础上,调节脂肪水平为12%,分别添加15%的葡萄糖、蔗糖和糊精配制3组实验饲料。在流水式养殖系统中进行9周的大菱鲆生长实验。结果显示,各处理组大菱鲆成活率均高于95.24%,并且各组间无显著差异;对照组和糊精组大菱鲆的增重率(WGR)和特定生长率(SGR)均显著高于葡萄糖组和蔗糖组。各组间的日摄食率(DFI)没有显著差异。对照组和糊精组饲料效率(FE)显著高于蔗糖组,但葡萄糖组FE与其它各组无显著差异;各处理组间蛋白质和脂肪表观消化率(ADC)未受碳水化合物种类的显著影响,而可消化碳水化合物的ADC依次为:葡萄糖组>糊精组>蔗糖组(。葡萄糖组的能量ADC最高,蔗糖组的最低;除对照组肌肉脂肪含量显著高于其它各组外,碳水化合物的种类对大菱鲆肌肉常规组成及糖原含量无显著影响,但显著影响了肝脏的脂肪和糖原含量。大菱鲆肝脏脂肪含量依次为对照组>糊精组>蔗糖组>葡萄糖组,肝脏糖原含量依次为葡萄糖组>蔗糖组>糊精组>对照组;不同碳水化合物种类对大菱鲆幼鱼血浆葡萄糖含量没有显著影响,但显著影响血浆总氨基酸、胰岛素、总胆固醇(CHO)和甘油三酯(TAGs)的含量。结果表明,本实验条件下,大菱鲆对糊精的利用效率优于葡萄糖和蔗糖,并且不同种类的碳水化合物通过糖脂关联代谢等途径对大菱鲆幼鱼的体组成和血液生理生化指标造成一定的影响。     

Histidine nutrition and genotype affect cataract development in Atlantic salmon, Salmo salar L

The aim of this study was to investigate effects of dietary levels of histidine (His) and iron (Fe) on cataract development in two strains of Atlantic salmon monitored through parr-smolt transformation. Three experimental diets were fed: (i) a control diet (CD) with 110 mg kg(-1) Fe and 11.7 g kg(-1) His; (ii) CD supplemented with crystalline His to a level of 18 g kg(-1) (HD); and (iii) HD with added iron up to 220 mg kg(-1) (HID). A cross-over design, with two feeding periods was used. A 6-week freshwater (FW) period was followed by a 20-week period, of which the first three were in FW and the following 17 weeks in sea water (SW). Fish were sampled for weighing, cataract assessment and tissue analysis at five time points. Cataracts developed in all groups in SW, but scores were lower in those fed high His diets (P < 0.05). This effect was most pronounced when HD or HID was given in SW, but was also observed when these diets were given in FW only. Histidine supplementation had a positive effect on growth performance and feed conversion ratio (P < 0.05), whereas this did not occur when iron was added. Groups fed HD or HID had higher lens levels of His and N-acetyl histidine (NAH), the latter showing a marked increase post-smoltification (P < 0.05). The HD or HID groups also showed higher muscle concentrations of the His dipeptide anserine (P < 0.05). There was a strong genetic influence on cataract development in the CD groups (P < 0.001), not associated with tissue levels of His or NAH. The role of His and His-related compounds in cataractogenesis is discussed in relation to tissue buffering, osmoregulation and antioxidation.     

Effects of dietary ascorbic acid/iron ratio on some production traits, lipid peroxide state and amount/activity of the glutathione redox system in African catfish Clarias gariepinus (Burchell) fingerlings

African catfish Clarias gariepinus (Burchell) fingerlings (3.16–3.92 g initial body weight) were investigated for 30 days in four different groups using different amounts of l ‐ascorbic acid (AA) and iron (supplied as FeC₆H₅O₇) in their feedings. Diet 1 (control): no addition of AA or iron; diet 2 (H‐AA/FE): high (600 mg kg^?1) AA and low (218 mg kg^?1) iron; diet 3 (H‐HE/AA): high (364 mg kg^?1) iron and low (200 mg kg^?1) AA; and an unfed group, which was investigated only for 15 days due to high mortality. The live weight gain, feed intake, specific growth rate (SGR; % body weight day^?1) and feed conversion rate (FCR) were measured or calculated. At the end of the experimental period, the whole body content of AA, iron, reduced glutathione (GSH), glutathione disulphide (GSSG) and malondialdehyde (MDA), as well as the glutathione peroxidase (GSHPx) activity, were measured. The production traits did not differ significantly as a result of the different AA and iron contents of the feed. AA content increased significantly in all the groups as compared with the initial value, except in the unfed group. The difference between the treated groups as compared with the control, with regard to the two AA/iron treated groups, was also significant. The iron content in the fish body increased significantly compared with the initial value, except in the unfed group. The difference compared with the control was significant only in the H‐FE/AA group. The difference between the groups that consumed low and high iron content diets was also significant. The GSH and GSSG content, as well as the GSH/GSSG ratio and GSHPx activity of the fish body, did not differ significantly as compared with the initial value or with the control. The lipid peroxide status, as measured by the MDA content, did not differ significantly either as an effect of the AA and iron supplementation, but decreased as an effect of ageing and starvation. It may be concluded that, under the present experimental conditions, the C. gariepinus fingerling tissue stores of AA and/or iron increased as a result of feed supplementation, but without altering the actual lipid peroxide status and the amount/activity of the glutathione redox system.     

Iron catalyzed oxidation of trout diets and its effect on the growth and physiological response of rainbow trout

Two experiments were conducted to determine 1) the effect of iron supplementation and the quality of fish oils on dietary lipid peroxidation and 2) the concurrent effects of diet rancidity and iron overload on the growth and physiological response of rainbow trout. Semi-purified diets supplemented with graded levels of iron (0–6250 mg/kg diet as ferrous sulphate) were fed to trout for 12–36 weeks. The malonaldehyde (MA) concentration of the test diets increased as the iron levels in the diets increased indicating that iron catalyzed lipid oxidation was occurring. However, when ethoxyquin was added to the oils, the increase in dietary MA level was significantly reduced. Fish oils with an initial high peroxide value were more susceptible to iron-catalyzed lipid oxidation. The concurrent effects of diet rancidity and iron overload (greater than 86 mg/kg) led to the development of unique histopathological signs, poor growth and high mortalities in the trout. In contrast, when diet rancidity was low (less than 10 µg MA/g diet), the toxic level of dietary iron was greater than 1380 mg/kg diet. The concentration of iron in trout tissues, and the hematocrit and hemoglobin concentrations increased as dietary iron levels increased and were not affected by the degree of diet rancidity.