Hatchery Feeding of Starter Diets to Broiler Chicks

This study examined hatchery feeding of starter diets differing in amino acid density and moisture on live performance measurements up to 37 d and processing measurements at 38 d. Eggs from a Cobb × Cobb 500 slow-feathering cross broiler strain were set in a common incubator and hatched. Chicks were feather-sexed, placed in 36 chick trays (25 chicks of each sex), and weighed by tray. One of 4 dietary treatments was administered (454 g/tray) in crumble form: 1) no feed; 2) feed containing 1.24% digestible Lys, 0.84% digestible TSAA, 0.80% digestible Thr, 23.2% CP, and 3,080 kcal/kg of ME; 3) feed containing 1.45% digestible Lys, 0.94% digestible TSAA, 0.84% digestible Thr, 26.0% CP, and 3,080 kcal/kg of ME; and 4) treatment 3 plus 100 mL of potable water added to the crumbles 5 min before administration in the trays. Chicks received feed treatments in trays in the hatchery, during transportation to the research facility, and in the research facility until placement (5 h of total tray feeding). Body weight gain at d 7 was increased in birds fed the high density diet alone or in combination with water as compared with birds that were fasted. Subsequent live performance, processing, and small intestine weights, however, did not differ among treatments. Lack of 37-d improvements (average 4.6-lb birds) to early feed allocation may be a result of diet composition, duration of diet allocation, and the genetic strain of bird used, because much literature has pointed to the importance of posthatch nutrition of broilers.     

玉米-豆粕型日粮中添加高剂量植酸酶对肉鸡养分利用率的影响

本试验研究了玉米-豆粕型日粮中添加高剂量不同水平的植酸酶对0~3和4~6周肉鸡养分利用率的影响。选用1日龄AA肉鸡公雏576只,随机分为6组,每组8个重复,每个重复12只。试验日粮分0~3和4~6周两个阶段,6个处理组:正对照组(前期为总磷0.69%,0.45% NPP;后期为总磷0.59%,0.35% NPP);负对照组(前期总磷0.60%,0.35% NPP;后期为总磷0.49%,0.25% NPP);4个试验组在负对照日粮中分别添加500、2000、8000和32000 FTU/kg 4种植酸酶水平。结果显示:①日粮添加高剂量不同水平的植酸酶显著影响生长前期(17~21日龄)肉鸡的钙、磷的消化利用率(P<0.05),随着植酸酶添加水平增加,钙的消化利用率显著增加(P＜0.05)。②日粮添加高剂量不同水平的植酸酶显著影响38~42日龄肉鸡磷的消化利用率(P＜0.05)。在负对照组日粮中随着植酸酶水平添加的提高,钙的消化利用率呈现先增加后降低的趋势,磷的养分利用率反而显著减少。③日粮添加高剂量不同水平植酸酶显著增加生长前期(17~21日龄)肉鸡的粗蛋白质的消化利用率和表观代谢能(P＜0.05),在生长后期(38~42日龄)对肉鸡的粗蛋白质的消化利用率和表观代谢能提高达到显著水平(P ＜0.05)。因此,高剂量不同水平的植酸酶显著提高肉鸡AME和粗蛋白质、钙、磷的消化利用率,添加高水平植酸酶可以适当调低日粮能量和蛋白质水平,日粮中总磷(tP)水平应低于NRC标准,减少无机磷和钙的添加量,以提高钙、磷在体内的存留量。     

Biological Availability of Phosphorus Sources in Prestarter and Starter Diets for Broiler Chicks

Two of the most widely used phosphate sources for broiler diets are defluorinated tricalcium phosphate (DFP) and dicalcium phosphate (DCP). Reports in the literature have shown that the biological availability of P in DFP for broilers and laying hens is lower than that in DCP. If this difference in bioavailability is even greater in young chicks, it might preclude the inclusion of DFP in prestarter and possibly starter diets. To address this question, 2 experiments were conducted to compare the P bioavailability of DFP and DCP in young broilers during the prestarter (1 to 8 d) and starter (9 to 15 d) periods. In Experiment 1, the first 3 treatments contained DFP, DCP, or raw rock phosphate, which were added to the diets to meet 0.32% available P (AP). Additionally, in 3 other treatments that served as positive controls, K₂ HPO₄ was added to meet AP levels of 0.24, 0.32, and 0.40%. No significant difference was observed at 4, 8, and 15 d of age between the foot ash percentage of chickens fed the DFP and DCP diets, indicating that the biological availability of P in DFP was not significantly inferior to that of DCP. In Experiment 2, chick responses to 2 levels of either DFP or DCP, added to meet AP levels of 0.28 and 0.34%, were compared with those of chicks receiving K₂ HPO₄, which was added to meet 3 AP levels (0.22, 0.28, and 0.34%). Foot ash results at 6 and 15 d of age indicated that the P utilization of chickens fed diets containing DFP was not significantly different to that of chickens fed the DCP diets. The difference in P bioavailability between DFP and DCP at 6 or 15 d of age was not greater than 10%. These results indicate that DFP can be satisfactorily utilized by young chicks during the prestarter and starter period and do not support the view that DFP should be excluded from diets for young chickens.     

玉米-豆粕型日粮中添加高剂量植酸酶对 肉鸡生长性能和血清生化指标的影响

本试验研究了玉米—豆粕型日粮中添加高剂量不同水平的植酸酶对0~3和3~6周肉鸡生长性能和血清生化指标的影响。选用1日龄AA肉公雏576只,随机分为6组,每组8个重复,每个重复12只。试验日粮分0~3和3~6周两个阶段,6个处理组分别为:正对照组(前期总磷0.69%,0.45% NPP;后期总磷0.59%,0.35% NPP);负对照组(前期总磷0.60%,0.35% NPP;后期总磷0.49%,0.25% NPP);4个试验组在负对照日粮中分别添加500、2000、8000和32000 FTU/kg 4种水平的植酸酶。结果显示,①日粮添加植酸酶水平显著影响前期(1~21日龄)平均日增重(P＜0.05),对采食量和饲料转化效率(F∶G)影响差异不显著(P＞0.05)。②日粮添加植酸酶水平对后期(22~42日龄)平均日增重和饲料转化效率(F∶G)影响差异显著(P＜0.05),添加植酸酶水平对采食量影响差异不显著(P＞0.05)。③在低磷日粮中添加高水平植酸酶8000 FTU/kg时,饲料转化效率最高。④随着植酸酶水平增加,21日龄肉鸡血清钙水平有降低趋势,血清磷水平显著增加(P＜0.05),血清碱性磷酸酶活性显著降低(P＜0.05),对总蛋白影响差异不显著(P＞0.05)。植酸酶添加水平影响42日龄肉鸡血清钙水平、总蛋白水平和血清碱性磷酸酶活性,对血清磷水平影响显著(P＜0.05)。因此,在低磷日粮中添加高剂量不同水平的植酸酶肉鸡的生长性显著增加,碱性磷酸酶的活性显著降低,添加8000 FTU/kg效果优于500、2000和32000 FTU/kg。     

Effect of Phytase Supplementation in Diets on Nutrient Digestibility and Performance in Broiler Chicks

A performance trial was conducted with broiler chicks to study the effect of phytase (PHY) supplementation in diets formulated with reduced AME, Ca, and P. The nutrient digestibility was determined during the 14- to 21-d and 28- to 35-d periods. The treatments consisted of 3 diets (NC1, NC2, NC3) differing in nutrient content and each diet with or without supplemental PHY (NC1, 0 or 500; NC2, 0 or 750; NC3, 0 or 1,000 U of PHY/kg feed) and 1 positive control diet (PC). Compared with the PC diet, negative control diets (NC) resulted in lower AME and apparent ileal amino acid digestibility for some amino acids. Phytase supplementation of the NC diets increased AME, apparent ileal amino acid digestibility, and apparent ileal crude protein digestibility. Phytase addition also increased mineral absorption in 21- and 35-d-old broilers fed NC diets. Reduced nutrient digestibility appears to be a factor in the weight gain and feed intake results. Reducing Ca and P content reduced feed intake in a stepwise fashion in the NC diets. Phytase increased feed intake and generally improved nutrient digestibility, which resulted in an increase in digestible nutrient intake. Averaged across NC diets, PHY improved body weight. Bone-breaking strength was the most consistent predictor of Ca and P reduction. All NC diets had significantly lower bone-breaking strength than the PC. Phytase supplementation of the NC diets gave bone-breaking strengths that were comparable to the PC. Diets with PHY had the highest bioeconomic index.     

肉鸡小麦型饲粮4种单酶复配效应的体外法评定

本试验旨在研究β-葡聚糖酶、木聚糖酶、纤维素酶和植酸酶用于肉鸡小麦型饲粮的最佳复合酶谱。采用单因素完全随机试验设计,将不同水平的β-葡聚糖酶(30、60、90、120、150和180 U/g)、木聚糖酶(200、400、600、800、1 000和1 200 U/g)、纤维素酶(200、400、600、800、1 000和1 200 U/g)和植酸酶(500、1 000、1 500、2 000、2 500和3 000 U/kg)分别添加于肉鸡小麦型饲粮中,采用模拟胃肠液体外消化试验,研究单酶的最佳添加水平;据此,采用4因子3水平L9(34)正交设计和体外法研究4种单酶复配效应,每种酶各设计3个添加水平:β-葡聚糖酶为100、150和200 U/g,木聚糖酶为900、950和1 000 U/g,纤维素酶为900、950和1 000 U/g,植酸酶为1 500、2 000和2 500 U/kg,以还原糖生成量、植酸磷降解率、饲料残渣总能为判定指标,确定4种单酶的最佳复合酶谱。结果表明:1~3周龄肉鸡小麦型饲粮中,当β-葡聚糖酶、木聚糖酶、纤维素酶添加水平分别为150、960、950 U/g时,分别获得最大还原糖生成量0.918、1.161、0.927 mg/g,当植酸酶添加水平为2 010 U/kg时,获得最大植酸磷降解率92.35%;4~6周龄肉鸡小麦型饲粮中,当β-葡聚糖酶、木聚糖酶、纤维素酶添加水平分别为150、950、960 U/g时,分别获得最大还原糖生成量0.920、1.160、0.929 mg/g,当植酸酶添加水平为1 940 U/kg时,获得最大植酸磷降解率92.23%;当4种酶的复合酶谱为β-葡聚糖酶150 U/g、木聚糖酶950 U/g、纤维素酶900 U/g、植酸酶2 500 U/kg时,还原糖生成量、植酸磷降解率、饲料残渣总能均获得较优值。综上,肉鸡小麦型饲粮中β-葡聚糖酶、木聚糖酶、纤维素酶和植酸酶的最佳添加水平,1~3周龄分别为150、960、950 U/g和2 010 U/kg,4~6周龄分别为150、950、960 U/g和1 940 U/kg,且2个阶段肉鸡小麦型饲粮中4种酶的最佳复合酶谱为β-葡聚糖酶150 U/g、木聚糖酶950 U/g、纤维素酶900 U/g、植酸酶2 500 U/kg。     

Evaluation of a Feed-Grade Enzyme in Broiler Diets to Reduce Pododermatitis

Nutritional and management interventions are needed to reduce the incidence of pododermatitis in poultry. In this study, enzyme (Allzyme Vegpro) supplementation of corn-soybean meal-based broiler diets was evaluated in an effort to reduce total N and NH₃ production and its effect on pododermatitis in broiler chickens. A total of 1,600 mixed-sex chicks were raised on floor pens in a design involving 2 × 2 × 2 arrangement of protein level [high or low], protein source [all vegetable (Veg) or vegetable plus animal (Veg + Ani)], and enzyme [with or without enzyme supplementation (0.06%)], on a 4-stage feeding program (4 replicate pens/treatment; 50 birds/pen). In addition to live performance, the feet were scored for incidence of lesions on all birds on 28, 42, and 57 d of age, and the severity was recorded as none, mild, and severe. Pooled gut samples were collected at 57 d of age to determine viscosities of fore- and hindgut contents. Pooled litter samples were analyzed for moisture, total N, and NH₃ production at 14, 28, 42, and 57 d of age. Live performance of birds did not vary among the treatments (P > 0.05). The incidence of pododermatitis was significantly affected by protein source at 42 d (P < 0.05), with birds fed all-vegetable diets showing higher incidence and severity than those fed vegetable plus animal diets. At 57 d of age, birds reared on all-vegetable diets with enzyme supplementation showed a lower incidence of mild footpad lesions compared with other treatments. Enzyme supplementation reduced viscosity of the gut contents irrespective of the protein level or protein source. Higher levels of litter NH₃ were observed with high-protein diets (28 and 42 d), all-vegetable diets (28 d), and with enzyme supplementation (28 and 42 d). In this study, enzyme supplementation had little effect on litter total N and NH₃ production levels, but reduced viscosity of the gut contents and severity of pododermatitis in older birds.     

Evaluation of Illinois Bundleflower (Desmanthus illinoensis) for Broiler Chicks

Illinois bundleflower (IBF; Desmanthus illinoensis) is a warm-season perennial legume native to the central plains of the United States and has potential as both a forage and grain crop. The objective of this research was to evaluate the potential of IBF seeds as a feed ingredient in broiler starter diets. One-day-old broiler chicks were fed 1 of 4 isocaloric and isonitrogenous experimental diets containing 0, 5, 10, or 15% IBF seed. Illinois Bundleflower seed is a high-protein (31.5% CP) feed ingredient with a Lys:Met similar to that of soybean meal. The TME content of IBF seed depends on the form in which it is fed. When fed ground, the TME_n content was determined to be 1,974 kcal/kg. When fed whole, with supplemental grit, the TME_n content was 1,067 kcal/kg. Inclusion of IBF seed in broiler starter diets had adverse affects on both feed consumption and BW gain, even at a 5% inclusion level. Further studies are required to determine whether IBF seed could be included in diets for older broiler chicks or laying hens.     

1～3周龄雌性肉仔鸡精氨酸需要量

本试验旨在研究饲粮中精氨酸水平对l～3周龄雌性爱拔益加(AA)肉仔鸡的影响,并运用二次曲线模型进行需要量估计.试验选用540只1日龄雌性AA肉仔鸡,随机分成6组,每组5个重复,每个重复18只鸡.6个组饲粮精氨酸水平分别为1.000%、1.125%、1.250%、1.375%、1.500%和1.625%.结果表明:精氨酸...     

Effects of Excess Methionine from Meeting Needs for Total Sulfur Amino Acids on Utilization of Diets Low in Crude Protein by Broiler Chicks

Failure to obtain optimum performance by broilers fed low CP diets supplemented with amino acids may be due to a number of factors, including potential toxic effects of amino acids in excess of requirements. The objective of the present study was to evaluate the effect of excess levels of Met on performance of broilers fed low CP diets. Corn and soybean meal of known composition were used to formulate diets with 22, 20, 18, and 16% CP with 100 and 110% of NRC recommendations. DL-Methionine was used to meet Met and TSAA requirements; the dietary levels of Met exceeded minimum needs. Within each CP level, 2 additional series were prepared. For one series, only the amount of DL-methionine needed to reach the Met requirement was added, leaving a calculated deficit of TSAA. For a second series, excess Met was replaced with sufficient Cys to meet Met and TSAA exactly. Each of the test diets and a 23% CP positive control were fed to 6 replicate pens of 5 male broiler chicks from 1 to 21 d of age. Performance of the birds fed 22% CP diets did not differ significantly from that of chicks fed the positive control. Chicks fed diets with less than 22% CP had significantly lower BW and increased FCR regardless of level of amino acid supplementation. There was no significant effect of Met status on performance, indicating that corn-soybean meal diets do not appear to be deficit in Cys and do not respond to levels of Met greater than minimum NRC recommendations for Met. Excess levels of Met in this study did not appear to contribute to the reduced performance at low CP levels.     

DL-羟基蛋氨酸钙相对于DL-蛋氨酸的生物学效价

试验采用肉仔鸡生产性能和胴体品质指标结合回归模型比较了DL-羟基蛋氨酸钙(DL-MHA-Ca)相对于DL-蛋氨酸(DLM)的生物学效价。选取792只体重相近且健康的AA肉仔鸡,随机分为11个处理,每个处理6个重复。DLM或DL-MHA-Ca按照等摩尔水平(0.03%、0.06%、0.10%、0.15%和0.21%)添加到仅缺乏蛋氨酸的基础日粮中。试验期35 d,分为7~21 d和22~42 d 2个阶段。结果表明:7~21 d和7~42 d,添加蛋氨酸源显著改善了肉仔鸡的体增重、饲料/增重、屠体重、胸肉重、胸肉率、腿肉重和全净膛重(P0.05);在等摩尔基础上,DL-MHA-Ca相对于DLM的生物学效价,7~21 d分别是71%(增重)和66%(饲料/增重);7~42 d则分别为63%(增重)、58%(饲料/增重)、74%(屠体重)、60%(胸肉重)、49%(胸肉率)、71%(腿肉重)和72%(全净膛重)。     

硒锌互作对肉鸡肝脏抗氧化酶活性的影响

选用 2 88只 1日龄健康 AA肉鸡为动物模型 ,随机分成 9组 ,每组 32只 ,动态研究了日粮中不同剂量硒锌互作对肝脏主要抗氧化酶 (CAT、SOD、GSH- Px)活性和脂质过氧化终末代谢产物丙二醛含量的影响 ,探讨了日粮中不同硒锌配比对肝脏抗氧化功能及肝脏功能的影响。饲料中硒、锌各设 3个水平 ,分别为硒 0 .0 8、0 .15、5 m g/ kg和锌 34、5 0、10 0 0 mg/ kg。试验结果表明 ,饲料中低硒 (0 .0 8mg/ kg)、低锌 (34 mg/ kg)、高锌 (10 0 0 m g/ kg)或高硒 (5 mg/ kg) ,尤其是低硒低锌和高硒高锌 ,均可引起肉鸡肝脏 CAT、SOD、GSH- Px3种酶活性下降 ;饲料中加入常硒 (0 .15 mg/ kg)和常锌 (5 0 mg/ kg) ,是肉鸡肝脏抗氧化酶活性维持正常水平的最佳剂量。     

辅酶Q10对肉仔鸡生产性能的影响以及对腹水症的敏感性研究

180只AA雄性肉仔鸡随机分为3组,每组6个重复,8日龄起分别饲喂代谢能为13.2MJ/kg的日粮,辅酶Q10添加量分别为0、20、40mg/kg.15～21日龄关闭水暖进行较低温处理(15～18℃)以诱发腹水症,并研究辅酶Q10添加对肉仔鸡生产性能的影响以及对腹水症的敏感性.结果表明在本试验条件下,肉仔鸡日粮中添加不同水平的辅酶Q10对生产性能的影响不显著,而能显著降低其对腹水症的敏感性.日粮添加辅酶Q10能够显著降低肉仔鸡腹水症的发病率和死亡率,降低肉仔鸡红细胞渗透脆性(EOF)(P≤0.05).虽然辅酶Q10添加与否对血液红细胞压积(PCV)没有显著影响,但40mg/kg的辅酶Q10添加量同20mg/kg的添加量相比,PCV值显著降低(P≤0.05),除了36日龄时添加40mg/kg辅酶Q10显著降低了肉仔鸡的肺动脉舒张压(PADP)外,各试验组肉仔鸡右心室内压(RVP)、肺动脉压(PAP)、右心室内压最大变化速率(±dp/dtmax)等均没有表现出显著变化,而40mg/kg的辅酶Q10组显著降低了腹水心脏指数(AHI)(P≤0.05).辅酶Q10的这种有益作用可能与其为心肌细胞充足供能、降低血液的红细胞渗透脆性有关.     

苜蓿加工产物中未鉴定生长因子（UGF）对肉仔鸡的影响

本文研究了苜蓿加工产物中未鉴定生长因子对肉仔鸡的影响，结果表明：自制的苜蓿汁粉可以作为专用未鉴定生长因子添加剂；用苜蓿叶粉作为未鉴定生长因子来源时，应考虑其中有害成分的影响；未鉴定生长因子提高增重不是由于蛋白质存留率提高。     

Influence of Temperature on the Arginine and Methionine Requirements of Young Broiler Chicks

Two experiments were conducted with Ross × Ross broiler chicks in battery brooders from 7 to 21 d of age to determine the Arg and Met requirements of young broiler chicks at control (25°C) and warm (35°C) temperatures. In both experiments, 1-d-old broiler chicks were fed a corn and soybean meal based starter diet for 7 d. Six replications (2 replicates in each of 3 rooms per temperature) with 8 chicks each were used for each treatment. In experiment 1, the basal diet was based on corn (34.52%), whey (26.96%), corn gluten meal (16.53%), soybean meal (11.74%), and poultry fat (23% of CP and 3.20 kcal/g of ME_n). Six levels of Arg (0, 0.1, 0.2, 0.3, 0.4, and 0.5%), supplementing the basal diet containing 0.95% Arg, were the dietary treatments. A broken-line linear model was used to estimate chick Arg requirements. Based on body gain and feed conversion ratio (FCR) data, respectively, the Arg requirements of young Ross × Ross broiler chicks raised at 35°C were 1.15 ± 0.03% and 1.13 ± 0.02%, whereas those of chicks at 25°C were 1.26 ± 0.03% and 1.27 ± 0.02%. In experiment 2, the influences of temperature and dietary Arg on the Met requirements of young broiler chicks were investigated. The basal diet was based on corn (53.45%), soybean meal (37.72%), and poultry fat (23% of CP and 3.20 kcal/g of ME). Experiment 2 had a 6 × 2 factorial arrangement, with the basal diet (0.35% Met and 1.52% Arg) supplemented with 6 levels of dietary Met (0, 0.05, 0.1, 0.15, 0.2, or 0.3%) and 2 levels of dietary Arg (0 and 1.0%). When chicks were fed a corn-soybean meal basal diet containing 1.52% Arg, the Met requirements of young Ross × Ross broiler chicks raised at 35°C were 0.43 ± 0.02% and 0.43 ± 0.03%, whereas those of chicks at 25°C was 0.43 ± 0.01% and 0.48 ± 0.03%, based on body gain and FCR data, respectively. When Arg levels were increased to 2.52%, the Met requirement of young Ross × Ross broiler chicks was greater at both temperatures (P < 0.05). The requirements of chicks raised at 35°C were 0.50 ± 0.02% and 0.49 ± 0.02% and at 25°C were 0.59 ± 0.03% and 0.57 ± 0.02%, based on body gain and FCR data, respectively. Temperature and amino acid balance may both affect the amino acid requirements of broilers.     

Effects of Betaine and Choline on Response to Methionine Supplementation to Broiler Diets Formulated to Industry Standards

A study was conducted to evaluate the Met-sparing effects of the methyl donors, choline (CHO) and betaine (BET). Male broilers of a commercial strain were fed corn-soybean meal-based diets formulated to meet nutritional levels typical of top broiler producers. Diets were fortified with a complete vitamin premix devoid of CHO. In test diets, Met levels were as formulated, or less 0.05, 0.10, 0.15, or 0.20% Met. Within each Met level, diets received no supplemental CHO or BET or 1,000 mg of CHO/kg, 1,000 mg of BET/kg, or a combination of 500 mg each of CHO and BET/kg. This resulted in a 4 × 5 factorial arrangement with each of the 20 treatments fed to 4 pens of 60 birds for a 56-d feeding trial. Samples of birds were processed at 42, 49, and 56 d to determine parts yield and dressing percentage. Intestinal segments were evaluated for tensile strength at these same ages.The dietary Met level had no significant impact on BW at 14 or 56 d of age, but at 35, 42, and 49 d reduction of the Met content resulted in loss of BW. Feed conversion was not affected by the Met level at 14 d but was significantly affected by reducing the Met level at all other ages. Breast meat yield was reduced in a linear manner by reductions in Met supplementation. The CHO or BET supplementation had no apparent sparing effect on Met needs but did improve feed conversion at 35 and 42 d. There was a positive effect of CHO and BET on breast yield that was independent of Met levels; CHO was as effective as BET for this purpose. No effect of CHO or BET on intestinal strength was observed in the present study.     

Effect of Soybean Oil Supplementation to Low Metabolizable Energy Diets on Production Parameters of Broiler Chickens

Two experiments were conducted to study the performance and carcass quality of broilers in response to varying composition of a diet low in ME, through the supplementation of graded levels of soybean oil. In an initial study, isocaloric (2,965 kcal/kg) and isonitrogenous (21.7%) corn-soybean diets were supplemented with 10, 20, or 30 g/kg of soybean oil. In a second experiment, diets containing ME levels of 2,940 and 3,040 kcal/kg were supplemented with soybean oil levels of 20 or 40 g/kg. In both experiments, supplementation of up to 30 or 40 g of oil/kg of diet resulted in increases of 175 and 120 g (P < 0.05) in BW gain and 97 and 91 g (P ≤ 0.06) in ready-to-cook (RTC) carcass weight at 49 d, respectively. There was a linear decrease (P < 0.05) in percentage deposition of abdominal fat pad only in diets containing 2,965 (Experiment 1) or 2,940 (Experiment 2) kcal of ME/kg with no significant changes in RTC carcass and whole breast or pectoralis major muscle yields and RTC carcass composition. Improvements in production parameters can be achieved in broiler chickens fed a low ME diet through the addition of moderate levels of soybean oil.