同一蛋白质水平不同赖氨酸与蛋氨酸比例对早期断奶藏羔羊复胃发育的影响

试验旨在研究18%蛋白质水平下,不同赖氨酸与蛋氨酸比例(Lys/Met)对早期断奶藏羔羊复胃发育的影响。选取(55±2)日龄断奶、体重(10.85±0.65)kg藏羔羊42只,随机分为3组,每组14只,公、母各半,分别饲喂18%蛋白质水平下不同Lys/Met比例的羔羊早期断奶料,试验期20 d。对早期断奶藏羔羊各胃室重量和组织形态指标进行了测定。结果表明,Lys/Met比例为3.1∶1时,藏羔羊复胃和瘤胃增重最好,瘤网胃乳头增长,瓣胃角化层、黏膜上皮和中央肌层增厚,皱胃胃底腺黏膜增厚效果最好。提示,早期断奶料营养水平影响藏羔羊复胃的生长发育,适宜的Lys/Met比例能够促进其良好的生长发育,在18%蛋白质水平下,藏羔羊早期断奶料Lys/Met比例为3.1∶1时效果最佳。     

饲粮蛋白质水平及赖氨酸/蛋氨酸对早期断奶藏羔羊生长性能及胃肠道组织形态的影响

本试验旨在研究饲粮蛋白质水平及赖氨酸/蛋氨酸(Lys/Met)对早期断奶藏羔羊生长性能及胃肠道组织形态的影响。试验选取(55±2)日龄、平均体重(10.85±0.65)kg断奶藏羔羊98只,随机分为7组,每组14只,公母各占1/2。设3个饲粮蛋白质水平(21.03%、18.02%和15.01%),调整蛋白质水平为18.02%和15.01%的饲粮的Lys/Met分别为2.6、3.1和3.6。试验期20 d。结果表明:1)随饲粮蛋白质水平的增加,藏羔羊采食量和平均日增重增加,腹泻率降低,藏羔羊瘤胃等复胃增重,小肠增长,瘤胃乳头和小肠绒毛发育得到优化;2)藏羔羊早期断奶饲粮在18.02%及15.01%蛋白质水平下,以Lys/Met为3.1的配比效果为最佳;3)蛋白质水平为18.02%(Lys/Met=3.1)的饲粮可替代21.03%的高蛋白质饲粮,蛋白质水平为15.01%(Lys/Met=3.1)的饲粮可替代18.02%的中蛋白质饲粮。结果提示,适宜的饲粮蛋白质水平及Lys/Met能够促进早期断奶藏羔羊胃肠道良好的生长发育,合理的Lys/Met能够降低其对蛋白质的需要量。     

益康XP替代抗生素对早期断奶藏羔羊应激和免疫的影响

选取早期断奶([55±2)日龄,体重(7.91±0.83)kg]藏羔羊42只,随机分为3组(每组14只,公母各半),饲喂基础日粮为粗蛋白和能量水平分别为18.02%和12.95 MJ/kg开口料。试验Ⅰ组为基础日粮,试验Ⅱ组为基础日粮+1%益康XP,试验Ⅲ组为基础日粮+0.03%莫能菌素。对早期断奶藏羔羊血清中反应应激的酶类指标(Cor、CK、LDH、AST、ALP)和免疫指标(IgG、IgA、IgM)进行了测定。试验结果表明:各试验组的Cor、CK、AST和LDH差异不显著(P>0.05),但Cor、CK试验Ⅱ组小于其它两组,AST试验Ⅱ组小于试验Ⅲ组、LDH试验Ⅲ组小于其它两组;ALP试验Ⅱ组明显大于试验Ⅲ组(P>0.05);试验Ⅱ组IgG、IgA、IgM高于试验Ⅰ组和试验Ⅲ组(P>0.05);试验Ⅱ组藏羔羊的日增重明显高于试验Ⅰ组和试验Ⅲ组,差异显著(P<0.01);试验Ⅱ组藏羔羊的日采食量高于试验Ⅰ组和试验Ⅲ组,试验Ⅱ组对藏羔羊的腹泻率明显低于试验Ⅰ组和试验Ⅲ组(P<0.05)。综合评价表明基础日粮中添加益康XP能减小藏羔羊的早期断奶应激,提高早期断奶藏羔羊免疫机能,是抗生素的一种优良替代品。     

断奶羔羊4种必需氨基酸限制性顺序和需要量模型探索

本试验旨在采用氨基酸部分扣除法研究断奶羔羊的4种必需氨基酸的限制性顺序和需要模型。选取50日龄断奶湖羊公羊100只随机分为5组,每组4个重复,每个重复5只羊。对照组为氨基酸平衡(PC)组,饲喂氨基酸平衡的开食料,4个试验组开食料在PC组的基础上分别扣除赖氨酸(PD-Lys组)、蛋氨酸(PD-Met组)、苏氨酸(PD-Thr组)和色氨酸(PD-Trp组),其余氨基酸含量保持一致。预试期为10 d,正试期为60 d。于羔羊60、90和120日龄称量体重,在120日龄每组随机选取6只羔羊进行屠宰。结果表明:1)60~120日龄和90~120日龄,PD-M et组羔羊平均日增重(ADG)显著低于其他各组(P0.05),饲料转化率(F/G)显著高于其他各组(P0.05);120日龄时,PD-Met组宰前活重、空体重、胴体重、眼肌面积、头重、蹄重及皮毛重均显著低于PC、PD-Thr和PD-Trp组(P0.05),但是5组间屠宰率(DP)、GR值和血液重差异不显著(P0.05)。2)以最佳ADG和F/G为评价指标时,60~90日龄和90~120日龄氨基酸限制性顺序为Met、Lys、Thr和Trp;而以最佳DP为评价指标时,120日龄氨基酸的限制性顺序为Trp、Thr、Lys、Met。3)以最佳ADG作为评价指标时,60~90日龄和90~120日龄Lys、M et、Thr和Trp的适宜比例分别为100∶44∶44∶8和100∶42∶38∶12;以最佳F/G作为评价指标时,60~90日龄和90~120日龄Lys、M et、Thr和Trp的适宜比例分别为100∶54∶45∶7和100∶47∶39∶12;以最佳DP为评价指标时,60~120日龄Lys、M et、Thr和Trp的适宜比例为100∶34∶38∶8。总之,饲粮必需氨基酸(Lys、Met、Thr和Trp)缺乏严重影响湖羊断奶羔羊的生长性能、屠宰性能和器官指数,特别是Met影响最为明显,其次是Lys,Thr和Trp影响较弱;不同评价指标(ADG、F/G和DP)和不同生长阶段得出的Lys、M et、Thr和Trp的限制性顺序和需要模型是不同的。     

大米蛋白粉替代乳清浓缩蛋白在断奶仔猪中的研究

试验选用体重相近的14日龄断奶仔猪(杜×长×大)24头,根据体重和性别随机分为4组。对照组饲喂基础日粮,试验1组、2组和3组分别用大米蛋白粉替代基础日粮中5%、10%和15%的乳清浓缩蛋白。研究了大米蛋白粉替代乳清浓缩蛋白对超早期断奶仔猪生长性能和血清血常规指标的影响。结果表明,超早期断奶仔猪日粮中,大米蛋白粉替代一定比例的乳清浓缩蛋白,断奶仔猪各组之间的ADFI、ADG和F/G差异均不显著(P>0.05),不过,在8￣14d,大米蛋白粉有提高仔猪ADG和降低料肉比的趋势;各组仔猪血液中红细胞、白细胞及血小板等血常规指标差异均不显著(P>0.05);其机体代谢水平和免疫机能差异也不显著。提示可以用大米蛋白粉替代一定比例的乳清浓缩蛋白应用于早期断奶仔猪。     

不同蛋白质水平饲粮对藏羔羊生长发育的影响

本试验旨在研究不同蛋白质水平饲粮对藏羔羊生长发育的影响。试验采用单因子随机试验设计,选取2月龄断奶、体重(20.80±2.75)kg的藏公羔羊90只,随机分成3个组(每组30个重复,每个重复1只羊),分别饲喂蛋白质水平为10.8%、12.0%和13.2%的试验饲粮。试验期为127 d,其中预试期7 d,正试期120 d。结果显示:1)12.0%蛋白质水平组藏羔羊的试验第60~90天及第90~120天日增重和平均日增重最高,料重比最低。2)12.0%蛋白质水平组藏羔羊的腹泻率及尿道感染率较低,死亡率最低。3)在试验第60天,12.0%蛋白质水平组血清总蛋白(TP)含量与10.8%和13.2%蛋白质水平组均没有显著差异(P0.05),但10.8%和13.2%蛋白质水平组之间差异显著(P0.05);在试验第90、120天,血清TP含量在12.0%和13.2%蛋白质水平组之间差异不显著(P0.05),但二者均显著高于10.8%蛋白质水平组(P0.05)。在各阶段,随着饲粮蛋白质水平的升高,血清葡萄糖(GLU)和总胆固醇(TC)含量均没有显著发生变化(P0.05)。4)12.0%蛋白质水平组的单位成本增重最高,达到73.05元/kg,总收入和净收入最高,净收入达到7 800.51元。本试验条件下,饲粮蛋白质水平影响早期断奶藏羔羊的生长发育,12.0%蛋白质水平可提高藏羔羊的日增重,降低料重比和死亡率,改善血清生化指标,提高生长性能,并降低饲养成本。     

限制性氨基酸对生长山羊血清胰岛素和总蛋白的影响

选用3只浏阳生长黑山羊(10.00±0.15 kg),测定各种氨基酸在山羊小肠表观消化率,依据肌肉氨基酸模式计算限制性氨基酸的灌注量.试验表明,生长山羊在实用日粮条件下需灌注Met,0.77 g/d;Lys,0.91 g/d;Leu,0.58 g/d.在此基础上,选用12只浏阳生长黑山羊(10.00±0.23 kg)按随机区组设计接受氨基酸混合液(对照组)以及分别减去3种氨基酸(Met、Lys和Leu)的灌注液(试验组).试验表明,减Met组与减Lys组血清胰岛素显著低于对照组(P《0.05),三处理组间及减Leu组和对照组间血清胰岛素浓度差异不显著(P》0.05).减少Met、Lys、Leu的灌注对血清总蛋白没有影响(P》0.05).     

鲁莱配套系断奶仔猪对赖氨酸需要量的研究

试验采用112头(35±2)日龄的鲁莱配套系断奶仔猪,随机分为4个处理组,每组4个重复,每个重复7头猪,研究饲粮不同赖氨酸水平(Lys:1.05%、1.15%、1.25%、1.35%)对鲁莱断奶仔猪生产性能和血清尿素氮的影响,确定鲁莱断奶仔猪赖氨酸的需要量。结果表明,当赖氨酸水平为1.15%时,料肉比和血清尿素氮浓度显著低于1.25%、1.35%组(P<0.05),鲁莱断奶仔猪的赖氨酸需求参数为饲粮的1.15%。     

不同蛋白质和氨基酸水平对肉鸭生产性能的影响

选用10日龄初质量约450 g的1 680只健康丽佳肉鸭,随机分为5组,每组3个重复,分别饲喂3个蛋白质水平日粮(对照组粗蛋白18%、MP组粗蛋白15.5%和LP组粗蛋白13.8%)和2个氨基酸水平日粮LL组(低赖氨酸组)和LM组(低蛋氨酸组),各组日粮代谢能均为12.14MJ/kg,试验期为15 d.试验表明,LP组日增质量比对照组显著降低,料肉比极显著增加,MP组与对照组间日增质量差异不显著;降低lys(赖氨酸)和Met(蛋氨酸)水平,均降低了生产性能,降低Met水平影响更大;从整个试验看,适当降低Lys和蛋白质水平(CP 15.5%)与对照组生产性能较为接近.因此,对10～25日龄肉鸭可适当降低日粮蛋白质和Lys水平,但应满足Met需要.     

日粮能量、蛋白水平对断奶仔猪生长性能、血液生化指标及激素水平的影响

本试验选用300头(28±1)日龄断奶的杜长大仔猪,按体重、胎次相近的原则分为5组,分别饲喂能量蛋白质水平不同的日粮,研究日粮能量和蛋白质水平对断奶仔猪生长性能、血液生化指标和激素水平的影响。结果表明:断奶仔猪日粮CP 19%,DE 13.59 MJ/kg时平均日增重最佳,CP 18%,DE 13.38 MJ/kg时饲料转化率最高,不同能量蛋白水平对仔猪血清尿素氮、胃泌素和皮质醇含量有显著影响(P<0.05)。     

Isoleucine and valine supplementation of a low-protein corn-wheat-soybean meal-based diet for piglets: growth performance and nitrogen balance

The effects of Ile and Val supplementation of a low-CP, corn-wheat-soybean meal-based piglet diet on growth performance, incidence of diarrhea, and N balance were studied using 60 Landrace x Duroc male piglets in a 4-wk experiment. The 60 individually caged piglets were divided into 5 dietary treatments, each consisting of 12 piglets. Diet 1 was a positive control diet (20% CP); diet 2 was a low-CP negative control diet (17% CP); diets 3, 4, and 5 were low-CP diets to which Ile, Val, or the combination of Ile and Val were added, respectively. All diets were supplemented with Lys, Met, Thr, and Trp to provide the required concentrations of these AA according to the 1998 NRC. Average daily gain and ADFI were similar among pigs fed the positive control, Val-added, and the Val plus Ile-added diets. On wk-2 and wk-4, fecal score was greater (softer feces) in piglets fed the 20% CP level compared with the remaining treatments (P < 0.01). Nitrogen intake was decreased (P < 0.0001) in pigs fed diets containing low levels of CP compared with pigs fed the 20% CP diet. Fecal N excretion (g/d) was decreased (P < 0.05) in piglets fed low-CP diets at wk 1 and wk 4 of feeding, and in urine at wk 4 of feeding. Crude protein levels or AA supplementation had no effect on N retention efficiencies. These results indicate that the supplementation of Val alone, or in combination with Ile, to a low-CP piglet diet with adequate levels of Lys, Met, Thr, and Trp is necessary to achieve maximum performance in pigs consuming corn-wheat-soybean meal-based diets.     

Apparent and standardized ileal digestibilities of amino acids for pigs fed corn- and soybean meal-based diets at varying crude protein levels

The objective of this study was to determine the effect of CP level in corn- and soybean meal-based diets on apparent (AID) and standardized ileal digestibility (SID) of AA. Six pigs (initial BW, 47.1 ± 1.0 kg) fitted with T-cannula at the distal ileum were fed 6 diets for 6 periods in a 6 × 6 Latin square design. The 6 diets consisted of a nitrogen-free diet and 5 corn- and soybean meal-based diets that contained CP of 68, 105, 141, 177, and 214 g/kg. Each period consisted of a 5-d adjustment period and 2 d of ileal digesta collection for 10 h on each of d 6 and 7. The ratio of corn:soybean meal was fixed at 3 to 2 by weight and cornstarch was added to dilute the CP concentration. Chromic oxide was added at 5 g/kg as an indigestible marker. The results showed basal endogenous loss ranged from 65 mg/kg of DMI for Met to 3,104 mg/kg of DMI for Pro. Proline and Gly (1,053 mg/kg of DMI) were the 2 most abundant AA in endogenous flow and together accounted for approximately 43% of the total endogenous AA flow. Of the basal ileal endogenous CP, total AA accounted for 82%. The AID were 80.9 to 84.7%, 85.1 to 87.4%, 72.9 to 79.5%, and 86.5 to 87.9% for Lys, Met, Thr, and Trp, respectively, with corresponding SID being 86.6 to 89.0%, 87.5 to 90.5%, 82.7 to 88.2%, and 90.2 to 94.6%, respectively, as dietary CP increased from 68 to 214 g/kg. There were linear increases in AID of N, Arg, Gly, Ile, Lys, Ser, Thr, Tyr, and Val (P ≤ 0.05) as CP increased and linear decreases in SID of N and all AA measured in this study except Lys, Met, and Pro (P ≤ 0.05). Both linear and quadratic effects were observed in AID for Pro (P < 0.05). In conclusion, the protein content of corn-soybean meal diets evaluated in the current study affected SID of most indispensable and dispensable AA, excluding Lys, Met, and Pro.     

Effects of feeding diets containing low crude protein and coarse wheat bran as alternatives to zinc oxide in nursery pig diets

Two experiments were conducted to determine the effects of crude protein (CP) level in diets containing coarse wheat bran (CWB) with or without pharmacological levels of Zn (provided by zinc oxide: ZnO) on growth performance and fecal DM of nursery pigs. In experiment 1, 360 barrows (Line 200 × 400, DNA, Columbus, NE, initially 5.6 kg) were allotted to 1 of 6 dietary treatments from d 0 to 21 after weaning with 5 pigs per pen and 12 pens per treatment. Treatments included a positive control diet (21% CP) with 3,000 mg/kg Zn in phase 1 and 2,000 mg/kg in phase 2; negative control (21% CP) with 110 mg/kg added Zn, and 4 diets containing 4% CWB and 110 mg/kg added Zn formulated to contain 21%, 19.5%, 18%, or 16.5% CP. The 2 control diets and 21% CP CWB diet contained 1.40% standardized ileal digestible (SID) Lys in phase 1 and 1.35% SID Lys in phase 2, while the 19.5%, 18%, and 16.5% CP diets contained 1.33, 1.25 and 1.20% Lys, respectively, in both phases. Pigs fed the positive control diet containing pharmacological ZnO had increased (P < 0.05) ADG and G:F compared with the negative control and the 21% CP CWB diet. Reducing CP (concurrently with SID Lys) in diets containing CWB decreased ADG and G:F (linear, P = 0.002); however, fecal DM increased (linear, P = 0.005). In experiment 2, two groups of 300 and 350 pigs, initially 7.0 and 6.2 kg, respectively, were used with 5 pigs per pen and 26 pens per treatment. The objective was to determine if adding back essential AA would improve growth performance of pigs fed the low CP diets. All dietary treatments were fed for 13 days, contained 4% CWB, and consisted of: (1) positive control with 2,000 mg/kg of Zn and 21% CP (1.35% SID Lys); (2) no ZnO and 21% CP; and 3 diets with no ZnO formulated to 18% CP and (3) 1.2% SID Lys; (4) 1.35% SID Lys by the addition of feed grade amino acids (AA), and (5) diet 4 with non-essential amino acids (NEAA; Gly and Glu). Pigs fed 21% CP with ZnO had increased (P = 0.001) ADG compared to those fed 18% CP (1.35% SID Lys) with high levels of feed grade amino acids or those fed the reduced SID Lys (1.2%) diet. Overall, G:F was improved (P < 0.001) for pigs fed 21% CP diets and those fed the 18% CP diet with NEAA compared to pigs fed 1.2% SID Lys and pigs fed high levels of feed grade amino acids. Fecal DM was increased for pigs fed the reduced SID Lys diet. In summary, pharmacological levels of Zn improve pig growth performance, but reducing CP (and subsequently SID Lys) decreased nursery pig growth performance.     

Evaluation of amino-acid supplemented diets varying in protein levels for laying hens

The ideal amino acid concept is increasing by being applied to laying hens. However, understanding the responses of modern laying hens to decreasing levels of dietary protein balanced with crystalline amino acids has yet to be examined. In this study, 5 dietary treatments varying in CP content (18.0, 17.5, 17.0, 16.5, and 16.0%) were formulated at a fixed dietary energy concentration of 2,825 kcal of ME/kg of feed. The crystalline amino acids, including Met, Thr, Ile, Val, Trp, and Lys, were supplemented according to an assumed ideal AA profile, and all diets contained 0.831% ileal digestible Lys. Irrespective of the CP levels, the ratio of Lys and the profile of different essential amino acids in relation to Lys remained similar in all the diets. A total of 540 21-week-old Hy-Line W36 hens were used with 6 replicates per treatment group. This trial was conducted for a period of 14 wk, ranging from wk 21 to 34. Egg production, daily egg mass, feed intake, and FCR were not affected in the low-protein groups. Egg weight and N excretion declined, whereas egg yolk color increased in the low-protein groups. Decreasing dietary CP was found to have no effect on blood ammonia and plasma uric acid. The application of the assumed ideal AA profile can lead to reduced dietary protein level, from 18 to 16%, without affecting the production performance of laying hens during 21 to 34 wk of age. The ratios of standardized ileal digestible Met, Met + Cys, Thr, Trp, Arg, Ile, and Val to standardized ileal digestible Lys were 50, 91, 70, 21, 104, 80, and 88%, respectively, in the assumed ideal AA profile. Excretion of nitrogen was significantly decreased from hens fed the protein-reduced diet without impairing BW.     

1～21日龄爱拔益加×罗曼肉杂鸡饲粮代谢能、粗蛋白质、蛋氨酸和赖氨酸适宜水平研究

本试验旨在研究1~21日龄爱拔益加(AA)×罗曼肉杂鸡饲粮代谢能、粗蛋白质、蛋氨酸和赖氨酸的适宜水平。采用L_9(3~4)正交试验设计,饲粮代谢能水平分别为11.70、12.12、12.54 M J/kg;粗蛋白质水平分别为19.00%、20.00%、21.00%;蛋氨酸水平分别为0.45%、0.50%、0.55%;赖氨酸水平分别为1.00%、1.10%、1.20%。选取1日龄AA×罗曼肉杂鸡864只,随机分为9组,每组6个重复,每个重复16只,试验期21 d。通过饲养试验、屠宰试验等方法检测不同营养水平饲粮的饲喂效果。结果表明:1)饲粮粗蛋白质、蛋氨酸和赖氨酸水平对试验鸡平均日增重有显著影响(P0.05),21.00%粗蛋白质水平组显著高于20.00%粗蛋白质水平组(P0.05),0.50%蛋氨酸水平组显著高于0.55%蛋氨酸水平组(P0.05),1.20%赖氨酸水平组显著高于1.10%赖氨酸水平组(P0.05)。2)饲粮代谢能水平对21日龄试验鸡活体总能含量有显著影响(P0.05),12.12 MJ/kg代谢能水平组显著高于12.54 MJ/kg代谢能水平组(P0.05);饲粮蛋氨酸水平对试验鸡活体粗脂肪含量有显著影响(P0.05),0.50%和0.55%蛋氨酸水平组显著高于0.45%蛋氨酸水平组(P0.05)。3)饲粮代谢能和粗蛋白质水平对21日龄试验鸡活体能量沉积率有显著影响(P0.05),11.70和12.12 MJ/kg代谢能水平组显著高于12.54 MJ/kg代谢能水平组(P0.05),21.00%粗蛋白质水平组显著高于20.00%和19.00%粗蛋白质水平组(P0.05);1.10%赖氨酸水平组的试验鸡活体赖氨酸沉积率显著高于1.20%赖氨酸水平组(P0.05)。4)饲粮赖氨酸水平对试验鸡血清葡萄糖、尿酸、尿素氮水平有显著影响(P0.05),1.00%赖氨酸水平组血清葡萄糖水平最高,显著高于1.20%赖氨酸水平组(P0.05),1.10%赖氨酸水平组血清尿酸水平最高,显著高于1.20%赖氨酸水平组(P0.05),1.20%赖氨酸水平组血清尿素氮水平最高,显著高于1.10%赖氨酸水平组(P0.05)。5)由回归分析得出1~21日龄AA×罗曼肉杂鸡饲粮代谢能、粗蛋白质、蛋氨酸和赖氨酸适宜水平的计算公式分别为ME=45.33W~(0.75)+183.84△W,CP=19.77 W~(0.75)+626.47△W,Met=1.44 W~(0.75)+10.31△W,Lys=3.01 W~(0.75)+21.28△W(M E为代谢能,W~(0.75)为代谢体重,△W为平均日增重,CP为粗蛋白质,Met为蛋氨酸,Lys为赖氨酸),根据公式计算得出饲粮代谢能、粗蛋白质、蛋氨酸和赖氨酸的适宜水平分别为11.90 MJ/kg、21.08%、0.51%和1.05%。     

The effect of different dietary ratios of lysine,arginine and methionine on biochemical parameters and hormone secretion in turkeys

We postulated that the use of optimal levels and proportions of Lys, Arg and Met in compound feed allows for optimal exploitation of the growth potential of contemporary slaughter turkey hybrids and reduces metabolic disorders. The aim of the study was to determine the effect of different proportions of Lys, Arg and Met in diets whose Lys content is in accordance with NRC recommendations, that is a low level, on selected parameters of protein, lipid and carbohydrate metabolism and on hormone secretion in turkeys. The lowest Arg content (90% Lys) in the diet resulted in an increase in plasma total cholesterol levels in the turkeys as compared to higher Arg content (100% or 110% of Lys), (2.50 vs. 2.09 vs. 1.83). Plasma HDL and creatinine concentration increased in turkeys fed diets with higher Arg content (100% and 110% Lys) compared to turkeys receiving the diet with the lowest Arg content (90% Lys). Compared to turkeys receiving the lowest and intermediate Arg content (90% and 100% Lys), the diet with the highest content of this AA (110% Lys) resulted in an increase in the plasma T4 level (71.21 vs. 86.60 vs. 128.2). The varied Arg and Met levels relative to Lys did not affect the secretion of neurotransmitters or hormones regulating glucose metabolism. At low levels of Met in the diet, an decrease in Arg relative to Lys from 100% to 90% caused a growth depression of turkeys (10.68 vs. 10.21 kg), which was not noted in the case of the higher Met content. When using the Lys level recommended by NRC in the turkey diet, the optimal Arg level is 100% and Met is 45% compared to Lys.     

Influence of dietary protein level, amino acid supplementation, and dietary energy levels on growing-finishing pig performance and carcass composition

Two experiments were conducted to determine the effects of feeding reduced-CP, AA-supplemented diets at two ambient temperatures (Exp. 1) or three levels of dietary NE (Exp. 2) on pig performance and carcass composition. In Exp. 1, 240 mixed-sex pigs were used to test whether projected differences in heat increment associated with diet composition affect pig performance. There were 10 replications of each treatment with four pigs per pen. For the 28-d trial, average initial and final BW were 28.7 kg and 47.5 kg, respectively. Pigs were maintained in a thermoneutral (23 degrees C) or heat-stressed (33 degrees C) environment and fed a 16% CP diet, a 12% CP diet, or a 12% CP diet supplemented with crystalline Lys, Trp, and Thr (on an as-fed basis). Pigs gained at similar rates when fed the 16% CP diet or the 12% CP diet supplemented with Lys, Trp, and Thr (P > 0.10). Pigs fed the 12% CP, AA-supplemented diet had a gain:feed similar to pigs fed the 16% CP diet when housed in the 23 degrees C environment but had a lower gain:feed in the 33 degrees C environment (diet x temperature, P < 0.01). In Exp. 2, 702 gilts were allotted to six treatments with nine replicates per treatment. Average initial and final BW were 25.3 and 109.7 kg, respectively. Gilts were fed two levels of CP (high CP with minimal crystalline AA supplementation or low CP with supplementation of Lys, Trp, Thr, and Met) and three levels of NE (high, medium, or low) in a 2 x 3 factorial arrangement. A four-phase feeding program was used, with diets containing apparent digestible Lys levels of 0.96, 0.75, 0.60, and 0.48% switched at a pig BW of 41.0, 58.8, and 82.3 kg, respectively. Pigs fed the low-CP, AA-supplemented diets had rates of growth and feed intake similar to pigs fed the high-CP diets. Dietary NE interacted with CP level for gain:feed (P < 0.06). A decrease in dietary NE from the highest NE level decreased gain:feed in pigs fed the high-CP diet; however, gain:feed declined in pigs fed the low-CP, AA-supplemented diet only when dietary NE was decreased to the lowest level. There was a slight reduction in longissimus area in pigs fed the low-CP diets (P < 0.08), but other estimates of carcass muscle did not differ (P > 0.10). These data suggest that pigs fed low-CP, AA-supplemented diets have performance and carcass characteristics similar to pigs fed higher levels of CP and that alterations in dietary NE do not have a discernible effect on pig performance or carcass composition.     

Nitrogen balance in barrows fed low-protein diets supplemented with essential amino acids

This study was conducted to determine the effect of addition of essential amino acids (EAA) to low-protein diets on N balance in barrows. Thirty barrows (Duroc × Yorkshire) with an initial BW of 36 kg were fed 5 corn- and soybean meal-based diets containing 13.6 to 18.2% crude protein (CP) for 10 d in a randomized complete block design. The 18.2% CP diet was formulated without addition of EAA (Lys, Met or Thr). The other diets contained 13.6 to 16.5% CP and were supplemented with EAA to provide 0.83% true digestible lysine equal to that in the 18.2% CP diet. Fecal, urinary, and total N excretion as well as N retention (g/d) decreased with decreasing dietary CP level (P < 0.01). The apparent digestibility of N was almost the same for the 18.2 and 16.5 CP diets, but the value was 2% higher (P = 0.07) than that for the 13.6% CP diet. These findings indicate that, compared with the 18.2% CP diets, supplementation with three EAA to the lowest-protein diets (13.6 CP) is inadequate for maximum intestinal protein digestion, amino acid absorption, or tissue protein deposition in growing barrows.