巴戟天多糖对胫骨软骨发育不良的肉鸡生产性能、胫骨指数、胫骨钙磷灰分和血清电解质的影响

目的旨在探究巴戟天多糖（Morinda officinalis How polysaccharides,MOP）对福美双诱导的胫骨软骨发育不良（tibial dyschondroplasia,TD）肉鸡生产性能、胫骨指数、胫骨钙磷灰分和血清电解质的影响。方法选取1日龄健康AA肉仔鸡120只,随机分为3组,每组4个重复,每个重复10只肉鸡。对照组（CON组）饲喂基础日粮;福美双诱导TD组（TD组）饲喂基础饲料,在第4天到第7天的饲料中添加100 mg/kg的福美双进行TD模型建立;巴戟天多糖组（MOP组）在接受TD造模处理后,在第7天到第15天的饲料中添加400 mg/kg的巴戟天多糖。结果与CON组相比,从试验开始到试验第7天,TD组肉鸡的平均采食量和平均日增重显著（P<0.05）降低,料肉比增加（P>0.05）;在试验第7天、第11天和第15天时,TD组肉鸡的胫骨生长板宽度和生长板宽度系数显著（P<0.05）增加,胫骨重量和胫骨长度显著（P<0.05）降低,胫骨重量指数降低（P>0.05）,胫骨灰分含量显著（P<0.05）降低,并且血清中电解质紊乱;与TD组相比,在试验第11天和第15天时,MOP组肉鸡的料肉比有降低的趋势（P>0.05）,MOP组肉鸡的生长板宽度和生长板宽度系数显著降低（P<0.05）,胫骨重量、胫骨长度和胫骨重量指数均显著（P<0.05）提高;在试验第11天时,MOP组肉鸡的胫骨灰分含量显著（P<0.05）提高;随着试验时间的延长,MOP组肉鸡的血清电解质含量趋于平衡。结论饲料中添加巴戟天多糖可以有效缓解和改善由福美双诱导的肉鸡TD症状。     

High vitamin D3 requirements in broilers for bone quality and prevention of tibial dyschondroplasia and interactions with dietary calcium, available phosphorus and vitamin A

1. Two experiments were carried out to investigate responses in performance and bone compositional and structural characteristics in broilers fed diets containing 4 concentrations of vitamin D3 (5, 20, 125 and 250 microg cholecalciferol/kg) at different concentrations of calcium, available phosphorus and vitamin A. 2. In experiment 1, body weight and tibia breaking strength were maximised at 14d with 250 microg vitamin D3/kg, tibia ash was maximised with 125 microg vitamin D3/kg. A high incidence of tibial dyschondroplasia (TD) was decreased to very low levels with 125 microg vitamin D/kg. 3. At 42d, performance and bone characteristics showed no response to vitamin D3 concentrations above 20 microg/kg. 4. Dietary vitamin A within the range 2-4 to 4.5 mg retinol/kg did not show any interaction with vitamin D3 status at either age. 5. In experiment 2, responses to vitamin D3 were strongly influenced by dietary calcium/available phosphorus. With 13 g calcium and 5 g available phosphorus/kg, performance and bone characteristics responded to vitamin D3 concentrations up to 125 microg/kg but more was needed at less optimal concentrations of calcium and available phosphorus. TD incidence was minimised with 250 microg/kg. 6. This study shows that high dietary concentrations of vitamin D3 can prevent TD. It is concluded that the vitamin D3 requirement of broilers up to 14 d of age at optimal dietary calcium and available phosphorus concentrations may be in the range 35 to 50 microg/kg for cortical bone quality and up to 250 microg/kg for prevention of TD. The vitamin D3 requirement for cortical bone quality after 14 d is not higher than 20 microg/kg. These requirements are much higher than earlier estimates and may be related to higher calcium requirements of modern broiler genotypes. Current regulations limiting maximum vitamin D3 concentrations in broiler starter diets may need to be reviewed.     

福美双对肉仔鸡肝功能和胫骨软骨发育不良的影响

研究了福美双对肉鸡胫骨软骨发育不良、血清相关酶活性、肝脏SOD、MDA及增重的影响。120只1日龄AA肉仔鸡随机分为3组，对照组、低浓度福美双组（50mg／kg）、高浓度福美双组（100mg／kg）。每组40只鸡，每组4个重复，每个重复10只鸡，试验进行28d。结果表明，饲料中添加福美双可以显著提高肉鸡TD发病率（P〈0．05），升高血清中AST、ALT和ALP的水平和肝脏MDA的含量（P〈0．05），降低肝脏SOD水平和肉鸡的生产性能。福美双可能通过改变肝脏的抗氧化状态，损害肉仔鸡的肝脏功能，影响骨代谢的相关酶活性，导致肉仔鸡胫骨软骨发育不良的发生。     

福美双对肉鸡生产性能、血清相关酶活性及胫骨软骨发育不良的影响

将120只1日龄AA肉鸡随机分为对照组、低浓度福美双组（50mg／kg福美双）、高浓度福美双组（100mg／kg福美双），试验进行28d。结果显示，饲料中添加福美双显著升高了血清AST、ALT和ALP水平（P〈0．05），提高了肉鸡胫骨软骨发育不良（TD）的发病率（P〈O．05），降低了肉鸡生产性能。表明福美双能通过损害肉鸡肝脏功能，影响骨代谢相关酶活性，而致发肉鸡TD。     

Effects of non-antibiotic feed additives on performance, tibial dyschondroplasia incidence and tibia characteristics of broilers fed low-calcium diets

This experiment was conducted to investigate and compare the efficacy of different feed additives on performance, tibial dyschondroplasia (TD) incidence and tibia characteristics of male broilers fed low-calcium diets. A completely randomized design, with six treatments and five replicates of five chicks per each was used. Experimental treatments were: (i) Basal diet containing recommended level of calcium (0.9%) as control treatment (Ctrl), (ii) low-calcium (0.67%) diet without any additive (LC), (iii) low-calcium diet + probiotic (2 g/kg diet), (iv) low-calcium diet + prebiotic (2 g/kg diet), (v) low-calcium diet + synbiotic [mix of probiotic and prebiotic (each 2 g/kg diet)], (vi) low-calcium diet + organic acid (1.5 g/kg diet). Birds were reared in an open-sided house system under natural tropical condition until 21 days of age. Feeding with low-calcium diet negatively influenced broiler performance (body weight, body weight gain and feed conversion ratio) and tibia characteristics, whereas dietary inclusion of all feed additives had beneficial effects on above-mentioned parameters and helped the birds to overcome problems related to low-calcium diets. Different treatments had no effect on TD incidence.     

Effect of diet with thiram on liver antioxidant capacity and tibial dyschondroplasia in broilers

1. An experiment was conducted to study the effect of thiram on liver antioxidant capacity and incidence of tibial dyschondroplasia in broilers. 2. One hundred and twenty Avian commercial broilers were allotted at random to three treatments: control group, low thiram group (50 mg/kg) and high thiram group (100 mg/kg). 3. Blood samples were collected to determine the activity of AST (aspartate aminotransferase). At the end of the trial, broilers were killed and liver samples were collected to determine the activity of SOD (superoxide dismutase), GSH-Px (glutathione peroxidase) and MDA (malondialdehyde) content, while the right proximal tibiotarsi were dissected in longitudinal section for assessment of tibial dyschondroplasia (TD) incidence and TD score. 4. The results showed that thiram increased the incidence of TD and TD scores, increased serum AST activity and MDA content of liver, and decreased the activity of SOD and GSH-Px in the liver. 5. They suggest that thiram causes TD in broilers by reducing liver antioxidation capability and damaging liver function; this may be one of the mechanisms by which thiram causes TD in broilers.     

维生素A、D对肉鸡钙磷代谢相关激素水平的影响

试验旨在研究维生素A、D对肉鸡钙磷代谢相关激素水平的影响。采用4×4完全随机试验设计,将8日龄健康艾维茵雄性肉鸡384只称重后随机分为16个处理组。每个处理组设3个重复,每个重复8只鸡,试验期5周。其中,维生素A设4个添加水平,分别为1 500、3 000、15 000和45 000 IU/kg日粮。维生素D设4个添加水平,分别为500、1 250、2 500和5 000 IU/kg日粮。结果表明,45 000 IU/kg维生素A组的肉鸡血清BGP含量相对于1 500 IU/kg维生素A组有显著的降低趋势(P=0.08);随着日粮维生素A水平的增加(1 500～45 000 IU/kg),血清CaBP浓度呈趋于显著的一次线性降低趋势(P=0.092),血清维生素D3与CT含量也呈现降低趋势(P=0.12,P=0.18),其中,以15 000、45 000 IU/kg维生素A组较低,尤以45 000 IU/kg维生素A组最低;血清PTH含量呈显著的一次线性增加(P=0.029)。随着日粮维生素D水平的增加,血清维生素D3含量呈趋于显著的一次线性增加趋势(P=0.093),血清BGP浓度也呈一次线性增加趋势(P=0.14);其中,以2 500和5 000 IU/kg时较高,5 000 IU/kg时最高。由此可知,日粮维生素A过量引起肉鸡骨骼钙磷代谢发生障碍与血清CaBP浓度的降低及PTH浓度的增加有关,也与过量维生素A对维生素D的拮抗作用有关。     

有机锌源对肉鸡生长性能和胫骨软骨症的影响

采用玉米－豆饼型饲粮研究有机锌源对肉鸡生长性能和胫骨软骨症（ＴＤ）的影响。结果表明,有机锌源与硫酸锌对肉鸡生长和饲料采食量均无显著影响,锌的补加提高了胫骨,中趾骨,胰Ｚｎ含量,有机锌源的补加并不影响骨灰含量,胫骨长度,不诱导肉鸡ＴＤ发病率上升。     

Effects of dietary chloride and magnesium on the incidence of tibial dyschondroplasia in chickens fed on Chinese practical diets.

1. The effects of varying the concentrations of dietary magnesium and chloride on the performance, incidence of tibial dyschondroplasia and tissue element contents of broilers fed on Chinese practical maize soya-bean meal diets was assessed. 2. Two concentrations of dietary chloride (1.5 and 3.5 g/kg) and 3 of dietary magnesium (2.0, 4.0 and 6.0 g/kg) were used to form 6 dietary treatments for a 21-d experimental period. 3. Results from this study indicated that the dietary ingredients of maize and soya-bean meals produced in the northeast of China may predispose or influence the susceptibility of chickens to tibial dyschondroplasia. 4. High dietary chloride induces a high incidence of tibial dyschondroplasia (P less than 0.05) which could be ameliorated by dietary magnesium supplementation. 5. Dietary magnesium plays an anti-rachitic role by improving the deposition of copper and zinc in the bone tissue. 6. Supplementation with magnesium to 4.0 g/kg is recommended for broiler diets in northeast China.     

ORIGINAL ARTICLE: Effect of the level of cholecalciferol supplementation of broiler diets on the performance and tibial dyschondroplasia

A study was conducted to evaluate four different cholecalciferol levels (NRC; modified), using diets supplemented with 200 (control), 1500, 2500 or 3500 IU/kg of cholecalciferol (VIT‐D3). Each treatment was assigned to 3 pens of 17 broiler chicks of a commercial strain grown in an open‐sided house with sidewall curtains. At 21and 42 days, BW and feed conversion (FCR) were determined. At 42 days, five birds per pen were slaughtered to evaluate tibia and toe ash of the right leg, and incidence and severity of tibial dyschondroplasia (TD) of the left tibia and also measured dressing percentage and breast meat yield. Serum calcium and phosphorus concentrations were also determined. Haemagglutination inhibition antibody titre against Newcastle disease virus and lymphoid organs weight/body weight ratio were also determined. At both 21 and 42 days, the BW of birds fed 1500 IU/kg to 3500 IU/kg of VIT‐D3 was significantly greater than birds fed 200 IU/kg. Similarly, better FCR was observed in birds those fed diets of high level of VIT‐D3. No significant difference was observed for mortality at any age. Better dressing percentage and breast meat yield were noted in birds fed diets containing 2500 or 3500 IU/kg VIT‐D3. Both tibia and toe ash contents were increased (p < 0.05) progressively with increased concentrations of cholecalciferol in feed. The incidence of TD (percentage of birds having TD scores greater than zero) was significantly (p < 0.05) influenced by level of 3500 IU VIT‐D3/kg at 42 days. The severity of TD in birds fed diets containing 200 IU/kg VIT‐D3 was apparently higher than birds fed diets with higher levels of VIT‐D3. Concentrations of calcium and phosphorus minerals in the serum increased progressively with the high level of VIT‐D3 supplementation to birds at both 21 and 42 days of age. Feeding levels of 1500 or 3500 IU of vitamin D3 did positively affect the immune system within the parameters measured. It may be concluded that performance, bone mineralization, blood chemistry and immunity against disease in broilers could be maintained when supplementing high level of VIT‐D3 incorporated in broiler diets.     

Avian tibial dyschondroplasia: a comparison of the incidence and severity as assessed by gross examination and histopathology.

The assessment of avian tibial dyschondroplasia (TD) in many recent studies is based on examination of slices of the proximal tibiotarsus with the naked eye. This study examines the incidence and severity of TD in broilers under four different dietary regimes and compares the efficacy of naked eye assessment with histopathological examination. The diets contained reduced levels of calcium relative to phosphorus with adequate (diet 1) and high (diet 2) levels of vitamin D3 supplementation; a very low calcium diet (diet 3) and a standard diet (diet 4) were also included. Gross examination suggested that TD was present in 80 per cent, 79 per cent and 27 per cent of tibiotarsi from birds on diets 1, 2 and 4, respectively. However, histological examination indicated TD, correspondingly, to be present in 18 per cent, 39 per cent and 6 per cent of tibiotarsi. Some birds on diet 1 exhibited physeal changes consistent with mild hypocalcaemic rickets. Many of the bone extremities which, grossly, were considered dyschondroplastic (diets 1, 2 and 4), histologically were shown to have an extensive hypertrophied zone with poor metaphyseal vessel penetration, but no cellular or matrix changes consistent with TD. This cast doubt on the validity of earlier studies of TD which relied solely on naked eye examination. The birds on diet 3 all demonstrated histopathology considered consistent with severe hypocalcaemic rickets and the present study suggests that in three-week-old broilers a moderately hypocalcaemic diet with a high level of vitamin D3 will not cause rickets but will increase the incidence and severity of TD.(ABSTRACT TRUNCATED AT 250 WORDS)     

饲粮添加不同水平维生素D_3对肉仔鸡生长性能和骨磷代谢利用的影响

本试验旨在研究饲粮中添加不同水平维生素D3(VD3)对肉仔鸡生长性能及骨磷代谢利用的影响。试验选用480只1日龄艾拔益加肉公雏,采用2×4双因子完全随机设计,设2个饲粮非植酸磷水平[0.45%和0.23%(实测值为0.44%和0.21%)]与4个VD3添加水平(0、1 000、2 000和4 000IU/kg),共8个组,每组6个重复,每个重复10只鸡。试验期21d。结果表明,与0.21%非植酸磷水平相比,0.44%非植酸磷水平显著提高肉仔鸡平均日增重(ADG)、平均日采食量(ADFI)、胫骨灰分含量和胫骨灰分磷含量(P0.05),显著降低料重比(F/G)和胫骨灰分磷绝对沉积率(P0.05);与不添加VD3相比,饲粮中添加VD3显著提高肉仔鸡ADG、15~21和1~21日龄ADFI、胫骨灰分含量和胫骨灰分磷绝对沉积率(P0.05),显著降低1~21日龄肉仔鸡F/G(P0.05);0.21%非植酸磷水平下,与不添加VD3相比,饲粮中添加VD3显著降低肉仔鸡死亡率(P0.05),显著提高21日龄肉仔鸡胫骨灰分磷重量(P0.05),添加2000IU/kg VD3显著提高14日龄肉仔鸡胫骨灰分磷重量(P0.05);0.44%非植酸磷水平下,与不添加VD3相比,饲粮中添加VD3显著提高肉仔鸡胫骨灰分磷重量(P0.05)。以上结果表明,饲粮中添加VD3可提高肉仔鸡的生长性能并降低死亡率,促进磷在骨骼中的代谢利用。     

饲粮铜和维生素A及其互作效应对肉仔鸡生长性能及抗氧化功能的影响

本研究旨在探讨铜和维生素A及其互作效应对内仔鸡生长性能及抗氧化功能的影响.试验选用1日龄艾维茵肉仔鸡448只,随机分为8组,每组4个重复,每个重复14只鸡.采用4×2(铜×维生素A)完全随机设计,饲粮铜的添加量分别为0、8、150、225 mg/kg,维生素A的添加量分别为1 500、5 000 IU/kg,分为2个生长阶段,前期为1～4周龄,后期为5～7周龄.结果表明:1)高铜( 150、225mg/kg)抑制了全期肉仔鸡生长性能,提高了全期血清铜蓝蛋白(Cp)和后期血清总超氧化物歧化酶(T-SOD)活性(P＜0.05).2)5 000 IU/kg维生素A组获得较好的生长性能,提高了全期血清T-SOD活性,降低了前期血清Cp活性(P＜0.05).3)铜和维生素A互作效应对前期体增重、血清Cp和T-SOD活性及全期料重比有显著影响(P＜0.05),且二者间存在互补作用.铜(8 mg/kg)×维生素A(5 000 IU/kg)组与铜(0 mg/kg)×维生素A(5 000 IU/kg)组对前期肉仔鸡获得良好生长性能和提高血清T-SOD活性均有促进作用,但对血清Cp活性有显著降低作用(P＜0.05).由此可见,在基础饲粮铜水平为16～23mg/kg时,铜的适宜添加量为前期8 mg/kg,后期0～8 mg/kg;全期维生素A的适宜添加量为5 000 IU/kg.     

日粮锌缺乏继发的生长限制对肉仔鸡维生素A代谢影响的研究

以玉米淀粉和低锌豆粕为主要原料构成含锌4．67mg／kg的半纯合低锌基础日粮，将150只1日龄艾维茵肉仔鸡随机分为3个自由采食组与2个限制采食组。其中．自由采食组日粮是在低锌基础日粮中分别添加0、5、80mg／kg的锌，各组的VA添加水平均为3000 IU／kg日粮。2个限制采食组的日粮锌添加水平为80mg／kg，其它营养成分及采食量控制到与相应的低锌组一致的水平。结果表明，日粮锌水平低于9．67mg／kg时，可引起肉仔鸡血清VA浓度的明显下降。日粮锌含量为4．67mg／kg时，血清VA浓度的下降既与缺锌本身有关，又与因缺锌继发的采食量下降有关；日粮锌含量为9．67mg／kg时，血清VA浓度的下降主要是由缺锌继发的采食量下降引起的。限制采食也可引起肉仔鸡血清VA浓度的下降，但对血清锌浓摩无明显的影响。     

Effects of dietary metabolisable energy, calcium and phosphorus on bone mineralisation, leg weakness and performance of broiler chickens

1. Performance, gait score (GS), tibial dyschondroplasia (TD), and tibia bone mineralisation and breaking strength were determined in 2880 male and female Ross 208 broilers fed on diets with two different concentrations of dietary metabolisable energy (ME) (11.00 or 12.00 MJ/kg) and 4 different concentrations of available phosphorus (aP) adjusted for dietary ME content (4.0, 4.5, 5.0 or 5.5 g/kg aP in starter and 3.5, 4.0, 4.5 or 5.0 g/kg aP in finisher diets containing 12.00 MJ/kg). 2. Tibia ash, calcium (Ca) and phosphorus (P) contents in broilers given diets with low ME (11.00 MJ/kg) were greater than those of broilers given diets with higher ME (12.00 MJ/kg). Tibia ash, Ca and P contents increased curvilinearly with increasing dietary aP content. The dietary aP level had no effect on GS. 3. Dietary concentration of ME or aP had no effect on tibia breaking strength. 4. Walking ability, as measured by GS, was negatively correlated with the body weight (BW) of tested birds at 23 and 35 d of age, but the dietary ME content or aP level had no significant effect on GS at 35 d of age. 5. The results indicated that bone mineral content had no clear correlation with the walking ability of broilers.     

Effect of casein phosphopeptide and 25-hydroxycholecalciferol on tibial dyschondroplasia in growing broiler chickens

1. An experiment was conducted to investigate the influence of dietary casein phosphopeptides and 25-hydroxycholecalciferol on the incidence of tibial dyschondroplasia (TD) in 14-d-old commercial broiler chickens. 2. Three hundred and twenty broiler chicks (one day old) were randomly allocated to one of 4 dietary treatments. A standard broiler diet was used as the control with the three experimental treatments receiving the control diet supplemented with 10 g casein phosphopeptide/kg, 14 g casein phosphopeptide/kg or 69 microg 25-hydroxycholecalciferol/kg. 3. Those birds fed the diets supplemented with 14g casein phosphopeptide/kg or 25-hydroxycholecalciferol had a lower incidence of TD than both the control and 10g casein phosphopeptide/kg treatments when assessed grossly. 4. The body weight of birds fed the 10 g casein phosphopeptide/kg diet or the 25-hydroxycholecalciferol diet was higher than birds fed the control diet. Although not significant, the body weight of birds fed the 14 g casein phosphopeptide/kg diet was also greater than the control birds. 5. The current experiment demonstrated that both casein phosphopeptide and 25-hydroxycholecalciferol can reduce the incidence of TD in the young broiler chicken. More research is required to explain the unexpected increase in body weight described above.     

磷源对福美双诱导的肉鸡胫骨软骨发育不良及骨骼钙、磷代谢的影响

本试验旨在研究磷酸一二钙(MDCP)和磷酸氢钙(DCP)对福美双诱导的肉鸡胫骨软骨发育不良(TD)及骨骼钙、磷代谢的影响。选取1日龄科宝(Cobb)肉雏鸡120只,试验1～21 d采用2因子设计,按磷源的不同分为2个处理(磷源DCP和MDCP),每个处理60只鸡;试验22～42 d采用2×2因子设计,将每种磷源按福美双的添加水平不同再分为2个处理(福美双水平为0和100 mg/kg),每个处理3个重复,每个重复10只鸡。福美双组在基础饲粮中添加100mg/kg福美双,于22～28 d饲喂,然后换喂对应不含福美双饲粮。结果表明:1)MDCP组肉鸡第35天TD评分相对DCP组有降低的趋势(P=0.09),但磷源对肉鸡第28和42天TD评分影响差异不显著(P>0.05)。福美双显著升高了肉鸡第28、35和42天TD评分(P<0.05)。2)福美双和磷源对肉鸡第35天胫骨灰分、钙和磷含量交互效应显著(P<0.05)。福美双诱导条件下,MDCP组肉鸡第35天胫骨灰分、钙、磷含量显著高于DCP组(P<0.05)。3)DCP组第35天血清甲状旁腺素含量高于MDCP组(P=0.12)。由此可见,相对DCP,MDCP对福美双诱导的TD发生有一定减缓作用,且与肉鸡骨骼钙、磷代谢密切相关。2种磷源对肉鸡最终TD评分影响差异不显著。     

维生素D对蛋雏鸭生长性能及免疫功能的影响

试验选取1日龄健康、体重相近的金定蛋雏鸭180只,随机分为5个处理组,每个处理6个重复,每个重复6只试鸭。采用玉米-豆粕型基础饲粮,Ⅰ组试验鸭饲喂基础饲粮,Ⅱ～Ⅴ组分别饲喂在基础饲粮中添加110、220、550、1000 IU/kg维生素D的试验饲粮,试验期4周。旨在研究不同维生素D添加水平对1～28日龄蛋雏鸭生长性能及免疫功能的影响,以探讨维生素D的适宜添加量。结果表明,添加550 IU/kg维生素D能显著提高蛋雏鸭平均日增重、降低料重比(P<0.05),显著提高IgA、IgG、T3、T4含量(P<0.05),并显著降低Cort含量(P<0.05)。由此可见,在玉米-豆粕型基础饲粮中添加适量的维生素D可提高蛋雏鸭生长性能及免疫功能。通过二次回归模型分析,估测蛋雏鸭日粮中维生素D的适宜添加量为523.1～560.6 IU/kg。     

Effects of dietary supplementation with vitamin C or vitamin E on cardiac lipid peroxidation and growth performance in broilers at risk of developing ascites syndrome

OBJECTIVE: To assess effects of high dietary amounts of vitamin C or vitamin E and oxidative stress on the heart and growth performance of broilers maintained at an altitude of 2,200 m above sea level. ANIMALS: 360 chicks (1-day-old broilers). PROCEDURE: Birds were randomly assigned to 3 groups (120 chicks/group). Each group of birds was fed a specific diet (control group, basal diet containing 12 mg of vitamin E (DL-alpha-tocopherol acetate)/kg of feed without additional ascorbic acid; vitamin E group, basal diet supplemented with 75 mg of vitamin E/kg of feed; and vitamin C group, basal diet supplemented with 400 mg of ascorbic acid/kg of feed) throughout the entire 7 weeks of the study. Feed consumption and body weight of chicks were recorded on a weekly basis. Nine randomly selected birds from each group were euthanatized each week. Remaining birds were euthanatized at the end of the study. Samples of cardiac tissues were obtained to measure thiobarbituric acid reactive substances (TBARS), an indicator of oxidative stress. RESULTS: Vitamin E-supplemented diets resulted in better growth performance, lower rates of feed conversion, and lower TBARS content. Vitamin C-supplemented diets resulted in lower feed consumption and lower rates of feed conversion. When used separately, neither of the vitamins had any effect on mortality attributable to ascites syndrome. CONCLUSION AND CLINICAL RELEVANCE: It is recommended that diets supplemented with vitamin C, vitamin E, or both be fed to broilers maintained at an altitude of 2,200 m above sea level to improve growth performance.