低蛋白质氨基酸平衡饲粮对黄羽肉种鸡产蛋性能、蛋品质、孵化性能和氮排放的影响

本试验旨在研究低蛋白质氨基酸平衡饲粮对黄羽肉种鸡生产性能、蛋品质、孵化性能和氮排放的影响。选用30周龄健康的快大型岭南黄羽肉种母鸡288只,根据体重和产蛋率相近原则,随机分为4个组,每组6个重复,每个重复12只鸡。各组饲粮粗蛋白质(CP)水平分别为16%(对照组)、15%、14%、13%,各组的赖氨酸、蛋氨酸、色氨酸、苏氨酸、缬氨酸、亮氨酸及异亮氨酸水平一致。试验期10周。结果表明:1)低蛋白质氨基酸平衡饲粮对黄羽肉种鸡末重、平均日增重、平均日产蛋量、料蛋比、平均蛋重、产蛋率、破蛋率和不合格蛋率均无显著影响(P>0.05)。2)低蛋白质氨基酸平衡饲粮对黄羽肉种鸡鸡蛋的蛋形指数、蛋白高度、哈氏单位、蛋黄重、蛋壳重和蛋壳厚度均无显著影响(P>0.05)。13%CP组的蛋黄颜色显著高于16%CP组(P<0.05)。3)低蛋白质氨基酸平衡饲粮对黄羽肉种鸡的雏鸡初生重、受精蛋孵化率、弱雏率和受精率均无显著影响(P>0.05)。4)13%、14%CP组的血浆尿素氮含量显著低于16%CP组(P<0.05),13%CP组的血浆尿酸含量显著低于16%CP组(P<0.05),13%CP组的粪便氮含量显著低于16%CP组(P<0.05)。由此可见,低蛋白质氨基酸平衡饲粮对黄羽肉种鸡的生产性能、蛋品质和孵化性能无负面影响,但能够降低血浆尿素氮、尿酸含量和粪便氮含量。本试验条件下,黄羽肉种鸡产蛋高峰期的饲粮CP水平可以降低至13%(补充7种必需氨基酸)。     

Use of industrial amino acids to allow low protein concentrations in finishing diets for growing Muscovy ducks

1. Three experiments were performed to assess the effects of decreasing protein concentration in the finishing diets for growing Muscovy ducks (8 to 12 weeks of age) by adding 4 essential amino acids (AAs, lysine, methionine, threonine and tryptophan). Experimental diets with crude protein (CP) contents from 105 to 142 g/kg, were compared with control diets providing 150 to 160 g/kg CP. In each trial, all diets were isocaloric. No significant modification in growth or carcase quality was observed when CP was greater than 124 g/kg in diets supplemented with the 4 essential AAs. 2. There was no advantage in supplying more than 4.3 g of digestible lysine per kg of diet (12.75 MJ ME/kg). When threonine was not added, breast yield decreased significantly (- 4.3%), while omitting tryptophan supplementation did not influence performance. 3. Furthermore, the experiments confirmed that reducing CP had little or no effect on food conversion efficiency and fatness in Muscovy ducklings, unlike the observed situation in broiler chickens.     

低蛋白饲粮补充4种氨基酸对肉用羊增重与肉质中氨基酸含量及血清学的影响

本试验旨在研究不同水平低蛋白饲粮补充过瘤胃氨基酸对育肥杜寒杂交肉用母羊增重、血清中蛋白与激素指标、肌肉中氨基酸含量和肉品质的影响,探索育肥肉羊饲粮低蛋白质含量的理论价值和应用效果。选用150只体重相近4月龄育肥杜寒杂交肉用母羊,随机分成5组,每组3个重复,每个重复10只羊。对照组饲喂粗蛋白质水平为16%的饲粮,试验组饲喂氨基酸平衡低蛋白饲粮,分为LP14组(饲粮CP=14%)、LP12组(饲粮CP=12%)、LP10组(饲粮CP=10%)和LP12+NPN组(饲粮CP=12%,添加1%尿素),各试验组饲粮中都添加过瘤胃赖氨酸、蛋氨酸、苏氨酸和精氨酸,使其和对照组饲粮中这4种氨基酸的含量保持一致,试验期90 d。结果表明:(1)不同水平的低蛋白饲粮在补充过瘤胃氨基酸后,对育肥杜寒杂交肉用母羊的试验末重、净增重和饲料转化比均无显著性影响(P>0.05),对照组干物质采食量高于各试验组(P<0.01),LP12+NPN组育肥羊干物质采食量高于其他低蛋白组(P<0.01)。(2)各组间试验羊血清总蛋白(TP)、球蛋白(GLB)、生长激素(GH)、类胰岛素样生长因子I(IGF-I)均无显著性差异(P>0.05),低蛋白组育肥羊血清尿素氮(BUN)显著低于对照组(P<0.01)。(3)各组肉羊背最长肌在肉色、滴水损失、pH0、pH24、熟肉率以及剪切力上均差异不显著(P>0.05)。(4)各组间试验羊的背最长肌中氨基酸的含量差异不显著(P>0.05)。在本试验条件下,降低育肥杜寒杂交肉羊饲粮粗蛋白质水平1~4个百分点并补充过瘤胃赖氨酸、蛋氨酸、苏氨酸、精氨酸和尿素,不会影响其增重情况、血清指标和肉品质,即低蛋白饲粮补充过瘤胃氨基酸可以满足肉羊育肥阶段的营养需要。     

Blood proteins and amino acids of female breeder turkeys fed on maize-soybean diets supplemented with methionine

Two hundred and six female breeder turkeys were fed on maize-soybean diets of equal energy content, containing 100, 120 or 140 g crude protein (CP)/kg to which DL-methionine was added at 0, 1, 2 or 3 g/kg diet in a factorial design. Serum albumin concentrations were found to be more sensitive measures of dietary protein adequacy than were total serum protein concentrations. Albumin concentrations at peak egg production were highest among birds fed on 120 and 140 g CP/kg diets. Four weeks later, they were highest only for those on the 140 g CP/kg diet. The elevated concentrations of blood threonine and lysine and the decreased concentration of glycine with increased dietary protein were in agreement with the data on egg production. These data suggested that a sub-optimal balance of dietary amino acids may have occurred.     

The response of broiler breeder hens to dietary lysine and methionine.

1. Broiler breeder hens were used in an experiment lasting 10 weeks (29 to 38 weeks of age) to measure the responses to dietary lysine and methionine, the main objective being to determine whether the coefficients of response to these amino acids were the same for broiler breeders and for laying pullets. 2. The hens were offered 150 g/d of one of 20 dietary treatments, 10 being lysine-limiting and 10 being methionine-limiting. The diets were mixed by diluting one of two concentrate (summit) mixes with a protein-free dilution mixture. The lysine-limiting summit diet was designed to supply approximately 1300 mg lysine/bird d, while the other supplied 520 mg methionine/bird d, when fed at 150 g/bird d. 3. Birds on the 5 lowest concentrations of both lysine and methionine did not consume the allotted amount of food, the amount decreasing, in a curvilinear fashion, to approximately 105 g/bird d. 4. The minimum egg weight recorded was 0.8 of the maximum, whereas the rate of lay of birds fed on the diets with the lowest amino acid concentrations was 0.2 of the maximum. 5. Using the Reading Model, the coefficients of response were calculated to be (for lysine) 16.88 E and 11.2 W, and for methionine, 7.03 E and 1.52 W, where E = egg output, g/bird d, and W = body mass, kg/bird. An average, individual, broiler breeder of 3 kg, producing 45 g of egg output per day, would need 793 mg of lysine and 321 mg of methionine daily. This intake of methionine is similar to that estimated by means of coefficients used for laying pullets, but the lysine requirement would be underestimated by 0.18 if the coefficients for laying pullets were used. 6. The coefficients for maintenance for both lysine and methionine, determined in this experiment, are considerably lower than values published previously, whilst the coefficients for egg output are, in both cases, higher. The resultant flock response curves therefore differed significantly from those in which the coefficients of response for for laying pullets were used.(ABSTRACT TRUNCATED AT 400 WORDS)     

30～38周龄产蛋鸡理想氨基酸模式的研究

本试验旨在通过4个剂量-反应试验,研究30～38周龄产蛋鸡对赖氨酸(Lys)、蛋氨酸(Met)、色氨酸(Trp)和苏氨酸(Thr)4种必需氨基酸(AA)的需要量及其比例.每个试验均采用360只海兰灰产蛋鸡,设5个处理,分别采食5个AA梯度水平的试验饲粮,每个处理6个重复,每个重复12只鸡.采用蛋公鸡回肠食糜法测定饲料原料的标准回肠可消化(SID)值.试验预试期14 d,正试期56 d.结果表明:海兰灰产蛋鸡的产蛋率、蛋重、日产蛋量和料蛋比与SIDLys、SID Met、SID Trp和SID Thr的摄入水平均有较好的折线回归关系;以日产蛋量为自变量(x),AA摄入水平为依变量(Y)分别建立的回归方程为:YSID Lys=51.60-0.041 6(682.5-x),R2=0.96;YsID Met=51.43-0.085(314.1-x),R2 =0.95;YSID Trp =51.17-0.155 4(163.0-x),R2=0.97;YsID Thr=52.85-0.057 6(499.5-x),R2=0.93.在饲粮粗蛋白质12.8％的条件下,以日产蛋量为参照指标确定的30 ～ 38周龄产蛋鸡的SID Lys、SID Met、SID Trp和SID Thr需要量分别为684、313、171和506 mg/(只·d).以日产蛋量为指标建立的30～38周龄产蛋鸡理想SID AA模式为:Lys:Met:Trp:Thr=100∶46∶24∶73.     

标准回肠可消化氨基酸模式下降低饲粮粗蛋白质水平对蛋鸡生产性能、蛋品质及氮平衡的影响

本试验旨在研究标准回肠可消化(SID)氨基酸(AA)模式下,降低饲粮粗蛋白质(CP)水平对海兰灰蛋鸡生产性能、蛋品质及氮平衡的影响。选取540只20周龄体重相近且健康的海兰灰蛋鸡,随机分为5个处理,每个处理6个重复,每个重复18只鸡,预试期1周,正试期12周,采食等代谢能(11.82 MJ/kg)、等赖氨酸(Lys,SID Lys为0.831%)、相同AA模式、不同CP水平(18.0%、17.5%、17.0%、16.5%和16.0%)的试验饲粮。结果表明:SID AA模式下,降低饲粮CP水平可极显著降低平均蛋重和CP摄入量(P<0.01),显著降低鸡蛋浓蛋白高度(P<0.05),显著降低蛋鸡摄入氮和排出氮(P<0.05),有提高氮表观利用率的趋势(P=0.05);数据偏相关分析表明,饲粮中SID AA模式外的精氨酸、苯丙氨酸和亮氨酸水平下降与平均蛋重下降显著相关(P<0.05),与浓蛋白高度下降无显著相关(P>0.05)。结果提示,SID AA模式下,降低饲粮CP水平,除影响平均蛋重和浓蛋白高度外,对其他生产性能、蛋品质及血液生化指标影响较小,平均蛋重的下降与低CP饲粮中精氨酸、苯丙氨酸和亮氨酸不足有关;AA平衡的低CP饲粮,可在维持较高生产性能的同时减轻蛋鸡粪氮排出。     

Effect of excess levels of methionine, tryptophan, arginine, lysine or threonine on growth and dietary choice in the pig

Six experiments were conducted with newly weaned pigs (8 kg) to evaluate the effects of 4% excesses of DL-methionine, L-tryptophan, L-threonine, L-lysine or L-arginine on growth or "choice" (i.e., self-selection) when added to 20% protein, corn-soybean meal (C-SBM) diets. Arginine was supplied as the free base and lysine as lysine acetate to avoid acid-base problems. In the growth study, gain was reduced 52, 31, 28, 16 and 5% by additions of methionine, arginine, tryptophan, lysine and threonine, respectively. Small decreases in gain/feed occurred in pigs fed diets with excess methionine or lysine. Feed intake depressions were evident in pigs fed excess methionine or excess tryptophan within 1 d after initiation of the growth trial. Self-selection studies revealed that pigs strongly preferred the control diet over any of the diets containing excess amino acids. Further studies indicated that pigs preferred diets with excess threonine, lysine or arginine over those containing an equal excess (i.e., 4%) of methionine or tryptophan. Moreover, there was a tendency for pigs to prefer the diet with excess threonine over the one containing excess lysine or arginine. Also, pigs clearly preferred the diet with excess methionine over the diet containing excess tryptophan. When given a choice between a protein-free diet and a C-SBM diet containing 4% excess tryptophan, pigs initially (d 0 to 4) preferred the protein-free diet, but later adapted to the extent that during the last 4 d of the 12-d trial they consumed more of the tryptophan-imbalanced diet than of the protein-free diet.     

Long‐term feeding effects of dietary protein levels on egg production,immunocompetence and plasma amino acids of laying hens in subtropical condition

The objective of this study was to determine the effect of protein levels on production performance, immune response, liver triglyceride and plasma amino acids profile of laying hens during 21–48 weeks of age. Two groups of commercial hens (Babcock B‐308) were fed with diets with different crude protein levels (14% and 18% CP). The high protein diet (18% CP) significantly increased production performance, essential amino acid intake, spleen weight (% of body weight), ND‐titre (haemagglutination‐inhibition test), serum albumin (g/dl), serum alpha‐globulin and plasma essential amino acids (except histidine) and decreased liver triglyceride (mg/g liver) in relation to the low protein diet (14% CP). In long‐term effect, therefore, this study suggested that adequate dietary condition of amino acids, particularly methionine and branch‐chain amino acids is necessary for sustaining normal immunocompetence and achieving maximum production performance.     

Ileal digestibility of amino acids in pigs fed barleys differing in protein content

The apparent digestibility of nitrogen and amino acids was measured by the ileal and faecal methods in pigs fed nine barleys differing in nitrogen content (from 1.73 to 2.16 per cent/DM). A positive (r = 0.87) and significant relationship was found between the apparent nitrogen digestibility at the end of the ileum and the crude protein content of barley. Generally, the higher the protein of the grain, the higher the ileal digestibilities of the amino acids. For most amino acids the faecal values were greater than the ileal ones. This being specially so for threonine, tryptophan, histidine and cystine belonging to the nutritionally important amino acid group. When the relationship between the amino acid and nitrogen digestibilities at the level of ileum is considered, the values were found to be similar to that of nitrogen in the case of tryptophan, higher for isoleucine, valine (both 2-3 units), cystine, histidine, leucine, methionine (all 5-6 units) and phenylalanine (10 units) and lower only for lysine and threonine (7-8 dig. units).     

理想氨基酸模式下低粗蛋白质饲粮对蛋鸡生产性能的影响

本试验旨在研究以理想氨基酸(AA)模式配制的低粗蛋白质(CP)饲粮对21～32周龄蛋鸡生产性能、蛋品质、全血氨浓度和血浆尿酸浓度及粪氮含量的影响.试验选用540只体重相近的健康海兰灰蛋鸡,随机分为5组,每组6个重复,每个重复18只鸡,分别饲喂等能量( 11.00 MJ/kg)的5种CP水平(17.00％、16.50％、16.00％、15.50％和15.00％)的饲粮,试验期12周.结果表明:在理想AA模式下降低饲粮CP水平,蛋鸡产蛋率显著提高(P＜0.05),平均蛋重有降低的趋势(P=0.06),但对平均日采食量、日产蛋重和蛋料比无显著影响(P＞0.05);降低饲粮CP水平极显著影响了蛋白高度和哈氏单位(_P＜0.01),显著影响了蛋黄颜色(P＜0.05),未显著影响蛋壳厚度和蛋壳强度(P＞0.05);饲粮CP水平对各鸡蛋成分均无显著影响(P＞0.05),但鸡蛋蛋白含量随饲粮CP水平的降低有降低的趋势(P=0.09);饲粮CP水平对血浆尿酸浓度及全血氨浓度均无显著影响(P＞0.05);降低饲粮CP水平极显著降低了蛋鸡粪氮含量(P＜0.01).由此可见,在理想AA模式下,适当降低饲粮CP水平可提高蛋鸡产蛋率,改善鸡蛋品质,降低粪氮含量.     

Protein and body weight accretion of chicks on diets with widely varying contents of soyabean meal supplemented or unsupplemented with its limiting amino acids

1. Two studies were conducted to evaluate the effects of relative deficiencies of methionine and threonine on the growth performance of 8- to 21-d-old chicks fed on isoenergetic diets containing a wide range of crude protein (CP) concentrations from dehulled soyabean meal (SBM). 2. Chicks fed on graded levels of SBM containing supplemental methionine and threonine (BAL) accreted whole-body protein more efficiently (P < 0.05) than those receiving graded levels of unsupplemented SBM (DEF), and superior (P < 0.05) growth performance was also obtained at lower CP levels when chicks were fed on the BAL diets. 3. Voluntary food intake increased between 30 and 220 g CP/kg in chicks fed on DEF diets, whereas food intake of chicks fed on BAL diets increased only between 30 and 100 g CP/kg, after which it decreased between 100 and 220 g CP/kg. 4. Protein efficiency ratio (g gain per g protein intake) decreased with each incremental increase in CP between 30 and 260 g CP/kg, regardless of whether diets were BAL or DEE 5. These data indicate that maintaining a balanced ratio of amino acids is a preferable approach when poultry producers are interested in employing low CP diets for economic, physiological or environmental reasons.     

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.     

Nitrogen metabolism and growth performance of gilts fed standard corn-soybean meal diets or low-crude protein,amino acid-supplemented diets

Two experiments were conducted to determine the CP concentration below which N retention and growth performance are reduced when low-protein, amino acid-supplemented, corn-soybean meal diets are fed. In a N balance trial (Exp. 1), 12 gilts (initial weight 41 kg) were fitted with urinary catheters and fed six different diets during three 7-d periods in an incomplete block design. The diets were: 1) 18% CP; 2) 14% CP + AA, 3) 16% CP; 4) 12% CP + AA; 5) 14% CP; and 6) 10% CP + AA. Amino acids (lysine, threonine, tryptophan, and methionine) were supplemented such that the concentrations in the low-protein diets were equal to those in their standard (4% CP higher) counterparts. Nitrogen retention (g/d) decreased (P < 0.01) as CP decreased, in both standard (27.10, 24.53, and 20.99) and low-protein (21.51, 19.18, and 15.83) diets, but was lower (P < 0.01) in low-protein diets. There were no differences among treatments (P > 0.05) in biological value (68.2% standard vs 71.0% low-protein). In a growth performance trial (Exp. 2), 36 gilts (initial weight 19.5 kg) were penned individually and fed one of six diets for 35 d in a randomized complete block design. Dietary treatments were a 16% CP standard diet and low-protein diets formulated to contain 15, 14, 13, 12, and 11% CP supplemented with crystalline lysine, tryptophan, threonine, and methionine to equal the total concentrations in the standard diet. Protein concentration affected (P < or = 0.05) ADG, ADFI, feed efficiency, fat-free lean gain, longissimus muscle area, plasma urea, and plasma concentrations of most essential AA. For most of these traits, the major difference was poor performance of pigs fed the 11% CP diet. Thus, in Exp. 1, at AA concentrations from deficient to excess, low-protein, amino acid-supplemented diets failed to produce the same N retention as the equivalent corn-soybean meal diets. However in Exp. 2, the same performance was obtained with 16, 15, 14, 13, and 12% CP. Based on these data, we suggest that N balance is more sensitive than growth to amino acid adequacy andthat other AA (e.g., isoleucine and valine) may limit growth performance when the protein concentration is reduced by more than four percentage units.     

饲粮缬氨酸水平对蛋鸡生产性能、蛋品质及血清生化指标的影响

本文旨在研究饲粮不同缬氨酸水平对蛋鸡生产性能、蛋品质及血清生化指标的影响,并探讨蛋鸡饲粮中缬氨酸的最适添加量.试验选用720只体重相近的40周龄的海兰褐壳蛋鸡,随机分成5组,每组4个重复,每个重复36只鸡,分别饲喂缬氨酸水平为0.6％、0.7％、0.8％、0.9％、1.0％的饲粮,试验期为56 d.结果表明:1)0.8％水平组料蛋比和1.0％水平组平均日采食量分别最低,与其他各组均差异显著(P＜0.05);各组产蛋率、平均蛋重和日产蛋均重均无显著差异(P＞0.05).2)0.8％水平组蛋壳强度最大,1.0％水平组蛋清蛋白质含量最低,与其他各组均差异显著(P＜0.05)或有显著的趋势(P＜0.10);各组蛋壳厚度、哈夫单位、蛋黄颜色、蛋白高度、蛋黄和蛋清相对重均无显著差异(P＞0.05).3)0.8％水平组血清葡萄糖含量最高,显著高于其他各组(P＜0.05);0.8％水平组血清尿素氮和尿酸含量最低,总氨基酸含量最高,与其他各组均有差异显著的趋势(P＜0.10).4)二次曲线分析表明:当饲粮代谢能为11.31 MJ/kg、粗蛋白质水平为15.81％、赖氨酸水平为0.77％时,以料蛋比为评价指标,产蛋高峰期蛋鸡缬氨酸需要量为0.78％,以蛋壳强度和血清白蛋白含量为评价指标,缬氨酸需要量分别为0.81％和0.75％.由此可知,基础饲粮中添加一定量的缬氨酸可降低产蛋高峰期蛋鸡料蛋比,增强蛋壳强度和提高血清葡萄糖含量.     

Prececal crude protein digestibility and absorption of amino acids from lupines in swine

The apparent precaecal (pc) digestibility of crude protein (CP) and the apparent pc absorption of the key amino acids (AA) lysine, methionine, cystine, isoleucine, threonine and tryptophan from two yellow sweet lupine (L. luteus) varieties (Bornova, Borluta) and one narrow-leafed sweet lupine (L. angustifolius) were determined with ileorectostomized pigs. When the influence of the basal diet (barley or protein free rations) was checked with regard to absorption there were significant differences in a few cases only. In comparison to soybean meal (SBM) the methionine of the lupines was significantly worse, the cystine significantly better absorbed. The CP and the other key AA of the lupines showed approximately the same or even slightly higher pc absorption than those of SBM. With the example of the pc-absorbable AA amounts it was shown that sweet lupines with an approximately equally high CP content as in SBM cannot completely substitute the latter even after lysine and methionine supplementation because the absorbable tryptophan is by far insufficient, and isoleucine and threonine make up only 75% in comparison to SBM. On the basis of the content of pc-digestible CP and pc-absorbable AA it becomes possible to substitute high-grade imported protein concentrates according to their ability of AA supply in the feeding of pigs completely or partly by home-made protein feeds.     

Effect of nutrient density on production performance, egg quality and humoral immune response of brown laying (Dahlem Red) hens in the tropics

A study was conducted to evaluate the effect of various concentrations of metabolizable energy (ME) with graded incremental levels of crude protein (CP) and essential amino acids (lysine and methionine) on production performance, egg quality and humoral immune response of Dahlem Red laying hens. Four experimental diets based on maize–soybean meal-deoiled rice bran were prepared. Diet 1 was fed as a control diet containing 2,600 kcal ME/kg, 15% CP, 0.75% Lys and 0.36% Met, and in the other three diets (D2, D3 and D4), concentrations of the above nutrients were increased by 2.5%, 5.0% and 7.5%, respectively. The levels of Ca (3.5%) and available P (0.32) were constant in all the diets. Each diet was offered ad libitum from 28 to 40 weeks of age to eight replicates containing six birds in each replicate. The egg production, egg weight and egg mass (in grams of egg per hen per day) were not affected by increasing the nutrient density up to 7.5% (2,795 kcal ME/kg diet) compared to the control group (2,600 ME/kg diet). However, feed consumption and feed efficiency (in grams of egg per gram of feed) were influenced by the variation in the nutrient density of diets. As the nutrient density increased by 5% (2,730 ME/kg diet), birds consumed significantly (P < 0.001) less feed. The birds in the 7.5% higher density group produced significantly (P < 0.05) higher egg mass per unit feed consumption compared to the control diet. Increasing nutrient density up to 7.5% had no effect on relative weight of albumen, yolk or shell. The Haugh unit, yolk colour and shell thickness were also not affected due to variation in the nutrient density. The humoral immune response measured at 34 and 40 weeks was progressively improved by increasing the nutrient density up to 5%. Increasing the nutrient density beyond 5% in the diet had no further influence on the humoral immune response. Based on the results of the present study, it can be concluded that Dahlem Red laying hens required 2,795 kcal/kg ME, 16% CP, 0.8% lysine and 0.4% methionine for eliciting optimum performance and immune response during 28 to 40 weeks of age.     

Dietary factors affecting the utilisation of protein by laying hens and their effects on the concentrations of certain nitrogenous constituents in the excreta

New techniques involving extraction with organic solvents and lithium carbonate solution have been used to fractionate nitrogenous components of the excreta from laying hens fed diets in which the supplementary protein was groundnut meal, poor‐quality fish meal or good‐quality fish meal. The effect of adding methionine or lysine or both to the groundnut diet was also studied.

The proportion of ingested nitrogen excreted as uric acid or urate was significantly higher when the dietary protein supplement was groundnut meal than when it was good‐quality fish meal or groundnut meal supplemented with both lysine and methionine. Nitrogen retention, egg production and the apparent digestibility of nitrogen were higher on diets containing good‐quality fish meal than on diets containing groundnut meal alone. Intermediate effects were obtained when feeding diets supplemented with poor‐quality fish meal of groundnut meal containing either lysine or methionine. The implications of these findings are discussed. The main differences in protein utilisation associated with variations in dietary protein quality were reflected in the proportions of ingested nitrogen excreted as urates and as protein. Other nitrogenous components of excreta examined showed little variation with dietary protein quality. Benefits derived from the addition of methionine and lysine to the groundnut diet were obtained mainly by a more efficient use of absorbed amino acids.     

Effects of low-crude protein diets supplemented with rumen-protected lysine and methionine on fattening performance and nitrogen excretion of Holstein steers

The objective of this experiment was to investigate the effects of low-crude protein (CP) diets supplemented with rumen-protected lysine and methionine on growth performance, nitrogen excretion, and carcass traits in Holstein steers. Steers consumed the following diets: (1) 17.2% CP on a dry-matter basis during the early period (from 7 to 10 months of age) and 14.5% CP during the late period (from 10 to 18 months of age; CON, n = 4, initial body weight [BW] 238 kg), and (2) 14.4% CP during the early period and 11.4% CP during the late period (AA, n = 4, initial BW 243 kg). The AA diet contains rumen-protected lysine and methionine. Except for CP intake, feed intake and body weight gain were not affected by dietary CP content. Total nitrogen excretion per metabolic BW tended to be lower (p < .10) in the early period and significantly lower (p < .05) in the late period with decreasing the feed CP content. Plasma urea nitrogen concentrations were lower in AA than CON. Carcass traits and total free amino acid contents of the longissimus thoracis muscle were not affected by dietary CP content. Adding rumen-protected lysine and methionine to a low-CP diet would reduce nitrogen excretion in fattening Holstein steers without affecting productivity.     

Effects of dietary protein,methionine and lysine on urinary amino acid excretion in turkeys1

1. Two experiments were conducted to determine the influence of dietary protein and amino acids on urinary excretion of amino acids and nitrogen in colostomised turkey hens.

2. Normal and colostomised turkeys 8 weeks of age were fed on control and high protein diets. Body weight gains of both types of birds were similar. Diet did not affect the amino acids in the urine significantly, but urinary nitrogen was higher with the high protein diet.

3. Normal and colostomised turkeys 10 weeks of age were fed a diet with either supplemental DL‐methionine or L‐lysine hydrochloride (each 20 g/kg diet). DL‐methionine depressed gain and resulted in considerable excretion of methionine in urine. Lysine had little effect on weight gain or urinary lysine.