Growth Performance,Meat Yield,and Economic Responses of Broilers Fed Diets Varying in Metabolizable Energy from Thirty to Fifty-Nine Days of Age

Two studies examined responses of broilers to diets varying in AME from 30 to 59 d of age. A 59-d termination allows for evaluation of energy needs applicable to “big bird” programs, because research on nutritional needs for such programs is warranted. Two experiments were conducted: experiment (exp.) 1 having low temperatures whereas exp. 2 used moderate temperatures. The treatments in exp. 1 and 2 were AME concentrations ranging from 3,175 to 3,310 kcal/kg with CP, TSAA, and Lys being identical across all treatments. In exp. 2, an additional treatment consisted of a diet containing 3,310 kcal of AME/kg with CP, TSAA, and Lys being increased by 4% of those specifications used in the other treatments so as to minimize differences in energy:CP ratio.In both experiments, feed consumption and conversion decreased linearly as dietary AME increased, but breast meat yield was reduced with the high AME diet and only increasing amino acids in exp. 2 ameliorated the negative effect. Live production costs and gross feeding margin (bird return over feed costs) were optimized in exp. 1 with 3,220 kcal of AME/kg of diet, but 3,310 kcal of AME/kg of diet and increased amino acids were needed in exp. 2 for improved monetary returns. In both experiments, broilers had similar caloric consumption indicating that these broilers can compensate to varying dietary AME concentrations within practical limits. These results demonstrated that the response to dietary AME was more pronounced under moderate ambient temperatures.     

Growth Performance,Meat Yield,and Economic Responses of Broilers Provided Diets Varying in Amino Acid Density from Thirty-Six to Fifty-Nine Days of Age

Providing broilers diets formulated to a high amino acid density early in life improves subsequent growth performance and meat yield. Diets formulated to high amino acid concentrations beyond 5 wk of age may increase breast meat yield but may not be economically justified. This study examined growth, meat yield, and economic responses of broilers provided diets varying in amino acid density from 36 to 59 d of age. Birds were given a 4-phase feeding program: starter (1 to 17 d), grower (18 to 35 d), withdrawal-1 (WD1; 36 to 47 d), and withdrawal-2 (WD2; 48 to 59 d of age). All birds were fed a common, high amino acid density diet to 35 d of age (HH). Broilers were provided diets characterized as being high (H), moderate (M), or low (L) in amino acid density for the WD1 and WD2 periods. Dietary treatments were HHHH, HHHM, HHHL, HHMM, HHML, and HHLL from d 1 to 59, with H, M, and L representing the diets fed during each of the 4 periods (starter, grower, WD1 and WD2).Cumulative feed conversion was improved when the HHHH feeding regimen was fed, whereas other final live performance measurements were not affected. Decreasing amino acid density (HHLL and HHHL) limited yields of breast fillets, tenders, and total white meat when compared with the HHHH regimen. As amino acid density decreased from HHHH to HHHM, HHMM, and HHML, carcass yield and breast meat yield were not affected. In general, providing the HHHH feeding regimen increased economic gross feeding margin compared with the other dietary treatments.     

日粮硒水平对22~42日龄肉仔鸡生长性能及肉品质的影响

为研究日粮硒水平对22~42日龄肉仔鸡生长性能和肉品质的影响,试验选用380只1日龄Arbor Acres（AA）肉公雏,1~21日龄统一饲喂同种正常添加无机硒的玉米-豆粕型日粮（含硒0.47 mg/kg）,于22日龄从中选取体重接近的336只鸡,随机分成6个处理组,每组7个重复,每个重复8只鸡。分别饲喂不添加硒的玉米-豆粕型基础日粮（对照组,含硒0.015 mg/kg）和在基础日粮中分别添加0.10、0.20、0.30、0.40和0.50 mg/kg硒（以亚硒酸钠形式添加）的试验日粮,试验期21 d。结果表明,日粮中添加不同硒水平对22~42日龄肉仔鸡平均日增重、平均日采食量和料重比均无显著影响（P>0.05）;对42日龄肉仔鸡屠宰率、全净膛率、胸肌率、腿肌率和腹脂率均无显著影响（P>0.05）;日粮中添加不同硒水平对42日龄肉仔鸡腿肌剪切力和胸肌肉色L^*值有显著影响（P<0.05）,其中添加0.50 mg/kg硒处理组肉鸡的腿肌剪切力最低,添加0.20和0.50 mg/kg硒处理组肉鸡的胸肌肉色L^*值最低,但其他肉质性状指标在各组间均无显著差异（P>0.05）。综上所述,玉米-豆粕型基础日粮中添加不同水平硒对22~42日龄肉仔鸡生长性能与42日龄肉仔鸡胴体性状均无显著影响,但日粮中添加0.50 mg/kg硒降低了腿肌剪切力和胸肌L^*值,对肉品质有一定的改善作用。     

包被肉桂油对1~21日龄肉鸡生长性能和回肠微生物区系的影响

为进一步探究肉桂油的应用效果,本试验在前期研究基础上探讨了饲粮中添加300 mg/kg包被肉桂油对肉鸡回肠菌群多样性和组成的影响。试验采用单因素设计,将132只1日龄科宝500肉鸡随机分成对照组和试验组,每个处理组6个重复,每个重复11只鸡（5只公鸡,6只母鸡）。对照组饲喂基础饲粮,试验组饲粮在基础饲粮中添加300 mg/kg包被肉桂油,试验期为21 d。结果显示,饲粮中添加300 mg/kg包被肉桂油对1~21日龄肉鸡生长性能无显著影响（P>0.05）。与对照组相比,试验组肉鸡21日龄回肠微生物的Shannon指数和Sobs指数显著增加（P<0.05）,Simpson指数显著降低（P<0.05）。两组回肠微生物共有的OTU数为133个,对照组和试验组独有的OTU数分别为4和135个。ANOSIM分析显示,肉鸡回肠微生物的组间差异大于组内差异（R=0.4896）且差异显著（P<0.05）。试验组回肠链球菌属相对丰度显著低于对照组（P<0.05）;两组回肠其他属细菌丰度差异均不显著（P>0.05）。综上所述,饲粮中添加300 mg/kg包被肉桂油有利于增加21日龄肉鸡回肠微生物多样性,降低链球菌属细菌的相对丰度。     

日粮能量、蛋白质水平对22~42日龄肉鸡WOD168公鸡生长与屠宰性能的影响

为研究22~42日龄肉鸡WOD168公鸡适宜的能量、蛋白质水平,以1 350只22日龄健康的肉鸡WOD168公鸡为试验对象,采用2×3因子设计,研究代谢能水平(ME分别为12.98、13.19 MJ/kg)、粗蛋白水平(CP分别为17.5%、18.5%、19.5%)及其交互作用对鸡生长性能与屠宰性能的影响。结果显示:CP水平为17.5%时42日龄体重显著降低(P<0.01);采食量、料肉比、营养摄入量等均表现出ME、CP的交互作用(P<0.05);屠体率随日粮能量水平提高而降低(P=0.057),而翅膀相对重随蛋白水平提高而提高(P=0.091)。研究提示,22~42日龄肉鸡WOD168公鸡在ME为13.19 MJ/kg、CP为19.5%时可获得最佳生长性能,而ME为12.98 MJ/kg、CP为17.5%时可获得较低料肉比及最佳屠宰性能。     

饲料中钙、磷水平对4～6周龄肉鸡骨骼生长的影响

选用800只21日龄白羽肉鸡,采用5×4二因子完全随机试验设计,随机分成20组,每组4个重复。在玉米-豆粕型日粮基础上添加5个水平钙(0.6%、0.8%、1.0%、1.2%和1.5%)和4个水平非植酸磷(0.35%、0.45%、0.55%和0.65%),研究饲料中不同钙、磷水平对4～6周龄肉鸡骨骼生长的影响。结果表明:胫骨强度、胫骨灰分及胫骨磷含量和日粮钙、磷水平呈显著正相关(P<0.05),但1.5%钙、0.6%钙和0.35%非植酸磷都显著降低胫骨强度、胫骨灰分及胫骨磷含量(P<0.05)。4-6周龄肉鸡达到最大胫骨强度时的日粮钙、非植酸磷添加水平分别为1.0%和0.45%。。由回归方程得出4-6周龄肉鸡胫骨灰分含量和胫骨强度达最大时的日粮钙、非植酸磷添加水平分别为0.99%、0.55%和1.02%、0.55%。     

Growth,Meat Yield,and Economic Responses of Broilers Provided Three- and Four-Phase Schedules Formulated to Moderate and High Nutrient Density During a Fifty-Six-Day Production Period

This study examined growth responses and meat yield of broilers provided a 3- or 4-phase feeding schedule formulated to moderate or high nutrient density. Four dietary treatments were implemented consisting of high or moderate nutrient density diets that were provided for the duration of 3 phases (1 to 17, 18 to 35, and 36 to 56 d) or 4 phases (1 to 17, 18 to 35, 36 to 46, and 47 to 56 d).Provision of a 3-phase schedule did not alter growth performance, meat yield, or diet cost per final BW. Broilers receiving high nutrient diets had improved growth rate and feed conversion from 1 to 35 d. In the 3-phase schedule, birds given the high nutrient density diets had advantages in BW gain and pectoralis minor breast weight. Market changes in meat prices impact differences in gross feeding margins between diets formulated to high or moderate nutrient density more than variation in diet cost.     

日粮钙或磷缺乏对22~42日龄肉仔鸡生长性能及胫骨组织结构的影响

试验在前期研究日粮钙（Ca）或磷（P）缺乏对1~21日龄肉仔鸡生长性能及胫骨组织结构影响的基础上,进一步研究其对22~42日龄肉仔鸡上述指标的影响。采用2（钙水平：0.90%和0.30%）×2（非植酸磷（NPP）水平：0.35%和0.18%）两因子完全随机试验设计,选取504只1日龄爱拔益加肉公雏随机分为4组,饲养至22日龄时给与不同日粮处理：正常对照组（0.90%钙+0.35%非植酸磷）、磷缺乏组（0.90%钙+0.18%非植酸磷）、钙缺乏组（0.30%钙+0.35%非植酸磷）及钙和磷同时缺乏组（0.30%钙+0.18%非植酸磷）,每个处理7个重复,测定22~42日龄肉仔鸡生长性能及28和42日龄胫骨组织结构。结果表明：与正常对照组相比,日粮钙或磷缺乏显著降低了肉仔鸡平均日采食量（ADFI）、平均日增重（ADG）和胫骨长度（P<0.05）,而显著增加了肉仔鸡料重比（F/G）和胫骨生长板增生区长度（P<0.05）;磷缺乏组肉仔鸡的22~28日龄平均日采食量和平均日增重与28日龄胫骨长度显著低于钙缺乏组及钙和磷同时缺乏组（P<0.05）;磷缺乏组肉仔鸡的22~28日龄死亡率显著高于其他各组（P<0.05）,该处理组肉仔鸡于28日龄时全部死亡;低钙水平显著增加了28日龄肉仔鸡胫骨生长板增生区长度（P<0.05）,而低磷水平显著降低了28日龄肉仔鸡胫骨生长板增生区长度（P<0.05）。综上所述,22~42日龄肉仔鸡生长性能及胫骨组织结构对日粮磷缺乏最为敏感,其次为钙缺乏或钙和磷同时缺乏;低钙水平可增加肉仔鸡胫骨生长板增生区长度而低磷水平则相反。     

能量和蛋白质水平对1～21日龄肉仔鸡生长性能、体蛋白质及体脂肪沉积的影响

本试验研究了1～21日龄肉仔鸡每日摄入不同水平的能量和蛋白质对其生长性能及体组分的影响,旨在确定日粮能蛋比(代谢能/粗蛋白质)与日粮蛋白质沉积为体蛋白质的效率(ep)间的函数关系及日粮能量以蛋白质形式和以脂肪形式沉积的效率.试验选取体重相近的1日龄爱拔益加(AA)肉仔鸡432只,按性别及日粮不同随机分为24个处理,每个处理3个重复,每个重复6只鸡.肉仔鸡每日限量饲喂,饲喂水平分别为正常采食量的95%、80%、65%、50%,每日定量供给肉仔鸡高、中、低3个水平的高蛋白质基础日粮及由饲喂水平决定的定量淀粉,进而使肉仔鸡每日采食能蛋比不同的12种日粮.试验期21 d,试验初和试验末分别进行屠宰试验,以测定肉仔鸡体成分.试验结果显示:1)日粮能量及蛋白质水平显著影响了肉仔鸡试末体重、体蛋白质重及体脂肪重(P<0.05);高蛋白质摄入水平下,随能量摄入水平的增高,公、母肉仔鸡试末体重、体蛋白质重及体脂肪重显著增高(P<0.05);中蛋白质摄入水平下,公、母肉仔鸡体脂肪重随能量摄入水平的增高显著增高(P<0.05),试末体重及体蛋白质重在50%～80%限饲水平时,随能量摄入水平的增高显著增高(P<0.05);低蛋白质摄入水平下,公鸡体脂肪重随能量摄入水平的增高显著增高(P<0.05),公、母肉仔鸡试未体重及母鸡体脂肪重在50%～80%限饲水平时,随能量摄入水平的增高显著增高(P<0.05),而体蛋白质重随能量摄入水平的增高无显著差异(P>0.05);2)日粮能量水平、蛋白质水平显著影响了肉仔鸡体增重、体蛋白质增重及体脂肪增重(P<0.05),其影响趋势与对肉仔鸡试末体重、体蛋白质重及体脂肪重的影响趋势相似;3)随日粮能蛋比的增加,日粮蛋白质沉积为体蛋白质的效率先线性增加,之后保持稳定,日粮能蛋比达到69.28 MJ/kg时,公、母肉仔鸡ep达到最大值,分别为0.64、0.63;4)公、母肉仔鸡日粮能量沉积为体蛋白质的效率分别为0.72、0.68,沉积为体脂肪的效率分别为0.59、0.65,公、母肉仔鸡平均沉积每克蛋白质分别需要能量32.88、34.82 kJ,沉积每克脂肪分别需要能量66.43、60.12 kJ.上述结果表明日粮能量及蛋白质摄入水平影响了肉仔鸡生产性能、体蛋白质及体脂肪沉积,日粮能蛋比影响了日粮蛋白质沉积为体蛋白质的效率,同时本试验确定了建立肉仔鸡机制性生长预测模型所需要的相关参数.