十二指肠灌注DL-蛋氨酸对肉牛营养物质消化率和血液指标影响的研究

根据基础日粮+待测氨基酸法,由十二指肠瘘管连续灌注DL-Met,通过日增重、氮平衡试验、小肠营养物质消化率指标和血浆游离氨基酸含量确定基础日粮条件下十二指肠氨酸最佳灌注量。试验结果表明:III组日增重最高,比I组提高15.27%(P<0.05)II组和III组沉积氮、沉积氮/可消化氮显著高于I组(P<0.05),其中III组高于II组;III组尿中尿素氮显著低于I组(P<0.05)。III组小肠氮的表观消化率最高,比I组高5.72%(P<0.05)。III组血浆氨氮显著低于I组(P<0.05)。血浆Cys和MetIV组显著高于其它3组(P<0.05),而Ser和Ile则相反。III组血浆Leu、Lys、BCAA和EAA显著低于其它各组(P<0.05)。肉牛十二指肠蛋氨酸最佳灌注量为13g/d。     

不同保护性蛋氨酸对奶牛挥发性脂肪酸和菌体蛋白的影响

选用3头装有永久性瘤胃瘘管和十二指肠瘘管的荷斯坦奶牛,试验分4个阶段。每个阶段分别饲喂日粮Ⅰ(基础日粮+保护性蛋氨酸Ⅰ30g/d)、日粮Ⅱ(基础日粮+保护性蛋氨酸Ⅱ30g/d)、日粮Ⅲ(基础日粮+保护性蛋氨酸Ⅲ30g/d)和日粮Ⅳ(基础日粮),研究棕榈油脂肪粉包被的蛋氨酸对瘤胃液挥发性脂肪酸和菌体蛋白的影响。结果表明:对挥发性脂肪酸有提高乙酸和丙酸浓度,降低丁酸浓度的趋势,但影响不显著(P>0.05);对菌体蛋白浓度略有提高,影响不显著(P>0.05)。     

饲粮不同蛋氨酸和赖氨酸水平对五龙鹅育成期生产性能及血浆尿酸和游离氨基酸浓度的影响

本试验选用42日龄健康五龙鹅,研究了饲粮中不同蛋氨酸和赖氨酸水平对其育成期生产性能及血浆尿酸和游离氨基酸浓度的影响。试验采用3×3二因子有重复设计,饲粮中蛋氨酸水平为0.33%、0.43%和0.53%,赖氨酸水平为0.7%、0.8%和0.9%。结果表明:①不同蛋氨酸水平对体增重和料重比影响显著(P<0.05),以0.33%水平时的体增重最大,料重比最低;不同赖氨酸水平对体增重和料重比影响不显著(P>0.05),但以0.7%水平体增重较高,料重比较低;不同蛋氨酸和赖氨酸水平对饲料消耗影响均不显著(P>0.05)。蛋氨酸与赖氨酸之间的交互作用对体增重和料重比影响显著(P<0.05)。②不同蛋氨酸水平对血浆尿酸含量影响显著(P<0.05),蛋氨酸水平为0.53%时血浆尿酸含量最高,为0.33%时含量最低;不同蛋氨酸水平对血浆蛋氨酸、赖氨酸、总必需氨基酸和总非必需氨基酸含量的影响均不显著(P>0.05),但对总游离氨基酸含量的影响显著(P<0.05)。不同赖氨酸水平对血浆尿酸含量影响不显著(P>0.05),但当赖氨酸水平为0.7%时血浆尿酸含量最低;不同赖氨酸水平对血浆蛋氨酸、赖氨酸和总必需氨基酸含量的影响均不显著(P>0.05),但对总非必需氨基酸和总游离氨基酸含量的影响显著(P<0.05)。蛋氨酸与赖氨酸间的交互作用对血浆尿酸含量影响极显著(P<0.01),对总游离氨     

瘤胃灌注大豆小肽对鲁西黄牛营养物质消化代谢的影响

试验选用4头安装永久性三位点瘘管的鲁西黄牛阉牛,采用4×4拉丁方试验设计,瘤胃分别灌注1 000 mL0.9%的生理盐水,100、200、300 g/d的大豆小肽,探讨其对肉牛营养物质消化代谢以及氮平衡的影响。结果表明:灌注大豆小肽对日粮脂肪(EE)、粗蛋白(CP)与酸性洗涤纤维(ADF)的表观消化率无影响(P>0.05);300 g/d组显著提高日粮干物质(DM)、有机物(OM)、中性洗涤纤维(NDF)的表观消化率(P<0.05);灌注小肽显著增加了尿氮的排出量(P<0.05),提高氮的表观消化率与氮沉积(P<0.05);200 g/d与300 g/d组显著降低了十二指肠氮流量占进食量的百分比(P<0.05);300 g/d组显著提高了血浆尿素氮和血浆葡萄糖含量(P<0.05)。试验结果表明,灌注大豆小肽能提高日粮营养成分的消化率,增加氮沉积,综合考虑各因素,在本试验中灌注量以200 g/d最佳。     

十二指肠灌注蛋氨酸对肉牛小肠氨基酸消化率的研究

根据基础日粮+待测氨基酸法,由十二指肠瘘管连续灌注DL Met,通过小肠氨基酸消化率确定基础日粮条件下十二指肠蛋氨酸最佳灌注量。试验采用4×4拉丁方设计,试牛饲喂相同的基础日粮,DL 蛋氨酸的浓度为0(Ⅰ组)、9(Ⅱ组)、13(Ⅲ组)和17(Ⅳ组)g/d,预试期12d,正试期7d,采用Cr2O3标记物法测定食糜流通量。结果表明:十二指肠灌注13g蛋氨酸(Ⅲ组)显著增加十二指肠Met、Cys、Pro、Lys以及TAA和EAA流通量(P<0 05),降低回肠Asp、Thr、Glu、Gly、Val、Ile、Phe、Lys和His的流通量,但差异不显著(P>0 05),显著提高Asp、Thr、Ser、Glu、Phe、His、Arg在小肠的表观消化率(P<0 05),证明本试验条件下十二指肠蛋氨酸最佳灌注量为13g/d。     

茉莉花香型贵妃母鸡肌肉中氨基酸含量的分析

本试验是对在日粮中添加茉莉花的贵妃母鸡肌肉中氨基酸含量的分析。选用120日龄贵妃母鸡120只,随机分为4组,每组30只母鸡。在基础日粮中添加茉莉花添加剂,按添加量的不同分为I(0%空白对照组)、II(1%)、III(2%)、IV(4%)4个组,进行为期45d的试验饲养。试验末期对4组贵妃鸡肌肉中氨基酸含量进行测定并作分析。结果表明:添加一定量的茉莉花添加剂能够提高贵妃母鸡胸、腿肌肉中各种氨基酸的含量,但是差异不显著(P0.05)。从胸肌测定结果看,胸肌氨基酸总量从大到小依次是IV(22.90g/100g)III(22.23g/100g)II(22.09g/100g)I(21.42g/100g);胸肌中必需氨基酸总量从大到小依次是IV(9.32g/100g)III(9.29g/100g)II(8.88g/100g)I(8.69g/100g);胸肌中鲜味氨基酸总量从大到小依次是III(8.50g/100g)IV(8.47g/100g)II(8.30g/100g)I(8.18g/100g)。从腿肌测定结果可知,腿肌氨基酸总量从大到小依次是II(21.13g/100g)III(20.91g/100g)IV(20.72g/100g)I(20.68g/100g);腿肌中必需氨基酸总量从大到小依次是II(8.70g/100g)III(8.42g/100g)IV(8.33g/100g)I(8.29g/100g);腿肌鲜味氨基酸总量从大到小依次是III(8.31g/100g)II(8.17g/100g)IV(8.11g/100g)I(8.05g/100g)。说明日粮中添加茉莉花对贵妃母鸡胸、腿肌肉氨基酸含量有所增加。     

复合异位酸对山羊瘤胃消化代谢的影响

试验研究日粮添加复合异位酸对山羊瘤胃消化代谢的影响。采用3×3拉丁方试验设计,选用3头安装有永久性瘤胃和十二指肠近端瘘管,平均体重为(25.4±0.75)kg的健康麻城黑山羊为试验动物。I组为空白对照,饲喂基础日粮I;II、II组分别饲喂含0.3%和0.6%复合异位酸(钠盐形式)的试验日粮。采用Co-EDTA标记法测定小肠食糜流通量。结果表明:各组瘤胃液pH差异不显著(P>0.05)I;I组NH3-N浓度显著低于对照组(P<0.05),显著提高了瘤胃乙酸和总挥发性脂肪酸(TVFA)浓度(P<0.05)并极显著提高了丁酸浓度(P<0.01),极显著提高了中性洗涤纤维(NDF)前胃消失量和消失率33.55%和12.25%(P<0.01);与对照组相比I,II组显著提高了瘤胃乙酸、TVFA浓度和乙酸/丙酸(P<0.05),并极显著提高了丁酸浓度(P<0.01),显著提高了NDF前胃消失率8.19%(P<0.05)。     

生长中期草鱼蛋氨酸需要量的研究

本试验通过研究饲料蛋氨酸水平对生长中期草鱼生长性能和消化吸收能力的影响,旨在确定生长中期草鱼的蛋氨酸需要量。选用平均体重为(259.00±0.48)g的草鱼900尾,随机分为6个处理(每个处理5个重复,每个重复30尾),分别饲喂蛋氨酸水平为2.19、4.72、7.18、9.67、12.21和14.69 g/kg的试验饲料,试验期49 d。结果表明:与蛋氨酸水平为2.19 g/kg时相比,提高饲料中蛋氨酸水平显著地提高了生长中期草鱼的增重、摄食量、饲料效率、特定生长率和蛋白质效率(P<0.05)。当蛋氨酸水平达到7.18 g/kg时,增重和特定生长率达到最大值。蛋氨酸水平显著影响生长中期草鱼的肝胰脏和肠道重量、肝胰脏和肠道蛋白质含量以及肠道长度(P<0.05),对肝体指数没有显著影响(P>0.05)。当蛋氨酸水平≥4.72 g/kg时,肝胰脏和肠道重量以及肠道长度在各处理间差异不显著(P>0.05)。肝胰脏和肠道蛋白质含量分别在蛋氨酸水平为9.67和12.21 g/kg时达到最大值。当蛋氨酸水平为7.18 g/kg时,肝胰脏和肠道胰蛋白酶、糜蛋白酶和脂肪酶活性均达到最大值。当蛋氨酸水平为4.72 g/kg时,肠道淀粉酶活性达到最大值,且与其他处理间差异达到显著水平(P<0.05)。蛋氨酸水平显著影响各肠段Na+,K+-ATP酶、碱性磷酸酶、γ-谷氨酰转肽酶和肌酸激酶活性(P<0.05)。由此得出,饲料中适宜水平的蛋氨酸可以提高生长中期草鱼的生长性能和消化吸收能力。以特定生长率为标识,当饲料胱氨酸含量为1.61 g/kg时,生长中期草鱼(259～498 g)的蛋氨酸需要量为10.41 g/kg饲料或34.71 g/kg蛋白质。     

不同能量蛋白水平日粮对妊娠后期西农萨能羊生产性能和血液生化指标的影响

本试验旨在研究不同能量蛋白水平日粮对妊娠后期西农萨能羊生产性能和血液生化指标的影响,以筛选出妊娠后期母羊最适的营养水平。试验采用2×2两因子完全随机区组试验设计,将60只处于妊娠期90 d、体重(60±2.4)kg的经产母羊随机分成4组,每组15个重复。日粮干物质蛋白水平分别设为14%、16%;能量水平分别为12.2 MJ/kg.DM和13.3 MJ/kg.DM。结果显示,试验母羊血浆总蛋白和尿素氮含量均与粗蛋白摄入量成正比,血浆白蛋白的含量则与之相反(P>0.05)。低蛋白高能量(14%、13.3 MJ/kg.DM)试验组的母羊具有较高产羔率(227%)、成活率(94.118%),该组母羊所产羔羊具有最大平均初生重(4.10±0.14)kg该试验组初乳具有较高乳总干物质(21.73%)、乳脂(7.71%)和乳蛋白含量(9.30%)(P>0.05),较低的乳糖含量(P<0.05)。试验表明,蛋白、能量水平分别为14%、13.3 MJ/kg.DM的日粮为妊娠后期西农萨能母羊最优的日粮组合。     

饲喂水平对育成生长期雄性北极狐生长性能、血液生化指标及机体能量沉积的影响

本试验旨在研究不同饲喂水平对育成生长期雄性北极狐生长性能、血清生化指标及机体能量沉积的影响。试验选取46只85日龄,平均体重为（3 198±281）g的健康雄性北极狐,其中6只北极狐作为试验初屠宰试验对照,另外40只北极狐随机分成4组（每组10个重复,每个重复1只）,分别为自由采食组（AL）（I组）、自由采食量的80%组（IR80）（II组）、自由采食量的60%组（IR60）（III组）和自由采食量的40%组（IR40）（IV组）。预试期7 d,试验期55 d,通过饲养试验、血清学试验、屠宰试验并结合化学分析方法来评定生长性能、血清生化指标及机体能量沉积的各项指标。结果表明：1）IV组100日龄体重极显著低于I和II组（P<0.01）,与III组差异不显著（P>0.05）,IV组115日龄、130日龄、145日龄体重和平均日增重（ADG）极显著低于其他3组（P<0.01）,3组间差异不显著（P>0.05）。随饲喂水平降低,平均干物质采食量（ADMI）呈极显著降低趋势（P<0.01）,III组料重比（F/G）极显著低于I和II组（P<0.01）,与IV组差异不显著（P>0.05）。2）IV组血清葡萄糖（GLU）显著高于III组（P<0.05）,与I和II组差异不显著（P>0.05）;IV组血清胆固醇（CHO）和低密度脂蛋白胆固醇（LDL-C）极显著高于其他3组（P<0.01）,I、II和III组间差异不显著（P>0.05）;IV组血清总蛋白（TP）和白蛋白（ALB）显著高于I和III组（P<0.05）,与II组差异不显著（P>0.05）;对血清甘油三酯（TG）、高密度脂蛋白胆固醇（HDL-C）、球蛋白（GLOB）、免疫球蛋白A（IgA）、M（IgM）和G（IgG）、补体3（C3）和补体4（C4）、胰岛素（INS）均无显著影响（P>0.05）。3）随饲喂水平减少,毛皮脂肪沉积及其产热显著降低,I和II组显著高于III和IV组（P<0.05）,II组毛皮增重和沉积总能量显著高于IV组（P<0.05）,与I和III组间差异不显著（P>0.05）;IV组胴体增重极显著低于其他3组,3组间差异不显著（P>0.05）;对毛皮蛋白沉积及其产热、胴体脂肪沉积及其产热、蛋白沉积及其产热和胴体沉积总能量均无显著影响（P>0.05）。采取适当限饲（IR60）降低了育成生长期北极狐血清中糖脂类指标含量,保证了机体正常的生长和健康状态,提高了饲料转化效率,进而增加了养殖生产效益。     

Effect of intraperitoneal administration of lysine and methionine on mohair yield and quality in Angora goats.

Eight mature Angora wethers (average BW 47.2 kg) were used in a 4 x 4 replicated Latin square design to evaluate responses to intraperitoneal (IP) administration of amino acids. The IP treatments consisted of saline (Control), methionine 1 g/d (Met), lysine 2 g/d (Lys), and methionine + lysine (Met + Lys). The amino acids dissolved in Control were infused continuously for the first 14 d of each 28-d period using peristaltic infusion pumps. Average d-28 grease and clean mohair yields (grams/100 square centimeters), and fiber diameter (micrometers) and length (centimeters) measurements during Control administration were 8.8, 7.6, 40, and 2.3, respectively. Mean clean mohair yield and fiber diameter increased by 5.3% (P less than .039) and 2.5% (P less than .067), respectively, with Met administration but were decreased by 9.2% (P less than .033) and 3.8% (P less than .001), respectively, by Lys administration; however, mean fiber length was increased (P less than .014) 21.7% by Lys infusion. The goats did not exhibit increased grease (P greater than .939) and clean (P greater than .477) mohair yields and fiber diameter (P greater than .619) when treated with Met+Lys. A N balance trial was conducted during d 10 through 14 of each period. Total retained N (grams per day) during Control administration was 18.4 and 24% greater than Met (P greater than .281) and Lys (P less than .061), respectively. When expressed as a proportion of N intake, retained N was lowest (P less than .127) in the Lys infusion group. Jugular blood ammonia N and plasma glucose and total protein concentrations were not affected (P greater than .10) by treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of ammonia load on methionine utilization by growing steers

Seven ruminally cannulated Holstein steers (194 +/- 16 kg) housed in metabolism crates were used in a 6 x 6 Latin square, with one additional steer, to study effects of ruminal ammonia load on methionine (Met) use. All steers received a diet based on soybean hulls (2.6 kg DM/d), ruminal infusions of 200 g/d of acetate, 200 g/d of propionate, and 50 g/d of butyrate, as well as abomasal infusion of 300 g/d of glucose to provide energy without increasing microbial protein supply, and abomasal infusions of a mixture (248 g/d) of all essential AA except Met. Treatments were arranged as a 3 x 2 factorial and included urea (0, 40, or 80 g/d) infused ruminally to supply metabolic ammonia loads and Met (2 or 5 g/d) infused abomasally. Supplementation with the greater amount of Met decreased (P < 0.05) urinary N excretion from 68.8 to 64.8 g/d and increased (P < 0.05) retained N from 22.0 to 27.5 g/d. Urea infusions linearly increased (P < 0.05) urinary N excretions, plasma urea concentrations, and urinary urea excretions, but retained N was not affected. The efficiency of deposition of supplemental Met, calculated by assuming that Met deposition is 2.0% of protein deposition (6.25 x retained N), ranged between 18 and 27% when steers received 0 or 80 g/d of urea, respectively. There were no (P > or = 0.40) effects of treatments on serum insulin or IGF-I concentrations. In our model, increasing ammonia load did not affect whole-body protein deposition in growing steers when Met was limiting.     

ORIGINAL ARTICLE: The effect of dietary methionine levels on endogenous nitrogen and endogenous amino acids flows in growing goats

The effect of dietary methionine (Met) levels on endogenous N and amino acids (AA) flows at different part of the digestive tract of growing goats was determined using a ¹⁵N isotope dilution technique. Three goats (25 ± 2.5 kg) were fitted with the ruminal, duodenal and ileal cannulae and allocated to three dietary treatments in a 3 × 3 Latin square design. The dietary treatments consisted of a total mixed ration containing three levels of Met (0.15%, 0.25% and 0.35%) respectively. It was found that at 0.15% Met level, the lowest flow in endogenous N and total AA at the duodenum and ileum occurred. The endogenous N secretion contributed to 26% and 23% of the duodenal and ileal total N flows, respectively, and the proportions were not affected by the dietary Met levels. The duodenal and ileal flows of endogenous total AA were 11.1, 11.8, 11.3 g/d and 2.9, 3.9, 4.1 g/d respectively. The average real digestibility of N was 65%, 87% and 95% in the forestomach, intestine and whole digestive tract respectively.     

Excess amino acid supply improves methionine and leucine utilization by growing steers

In 2 experiments, 6 ruminally cannulated Holstein steers (205 +/- 23 and 161 +/- 14 kg initial BW in Exp. 1 and 2, respectively) housed in metabolism crates were used in 6 x 6 Latin squares to study the effects of excess AA supply on Met (Exp. 1) and Leu (Exp. 2) use. All steers received a diet based on soybean hulls (DMI = 2.66 and 2.45 kg/d in Exp. 1 and 2, respectively); ruminal infusions of 200 g of acetate/d, 200 g of propionate/d, and 50 g of butyrate/d, as well as abomasal infusion of 300 g of glucose/d to provide energy without increasing the microbial protein supply; and abomasal infusions of a mixture of all essential AA except Met (Exp. 1) or Leu (Exp. 2). Periods were 6 d, with 2-d adaptations and 4 d to collect N balance data. All treatments were abomasally infused. In Exp. 1, treatments were arranged as a 2 x 3 factorial, with 2 amounts of l-Met (0 or 4 g/d) and 3 AA supplements (no additional AA, control; 100 g/d of nonessential AA + 100 g/d of essential AA, NEAA + EAA; and 200 g/d of essential AA, EAA). Supplemental Met increased (P < 0.01) retained N and decreased (P < 0.01) urinary N and urinary urea N. Retained N increased (P < 0.01) with NEAA + EAA only when 4 g/d of Met was provided, but it increased (P < 0.01) with EAA with or without supplemental Met. Both AA treatments increased (P < 0.01) plasma urea and serum insulin. Plasma glucose decreased (P = 0.03) with supplemental Met. In Exp. 2, treatments were arranged as a 2 x 3 factorial with 2 amounts of L-Leu (0 or 4 g/d) and 3 AA supplements (control, NEAA + EAA, and EAA). Supplemental Leu increased (P < 0.01) retained N and decreased (P < 0.01) urinary N and urinary urea N. Both AA treatments increased (P < 0.01) retained N, and they also increased (P < 0.01) urinary N, urinary urea N, and plasma urea. Serum insulin increased (P = 0.06) with supplemental Leu and tended (P = 0.10) to increase with both AA treatments. Supplementation with excess AA improved Met and Leu use for protein deposition by growing cattle.     

Supplemental methionine and urea for gestating beef cows consuming low quality forage diets

A study was conducted to evaluate Met requirements of late-gestation beef cows consuming low quality forages on the premise that inadequate supply of metabolizable AA may limit protein accretion during pregnancy. Five ruminally cannulated, multiparous late-gestation beef cows (490 +/- 27 kg), of predominantly Angus (> or =75%) with Hereford and Simmental breeding, were used in a 5 x 5 Latin square experiment to evaluate the effects of postruminal dl-Met supplementation on N retention, serum metabolites, and plasma AA concentrations during the third trimester of pregnancy. The basal diet was fed individually, and weights of refusals were recorded for N intake determination. Treatments consisted of no urea, urea (0.053 +/- 0.002 g/kg of BW daily), urea + 5 g of Met/d, urea + 10 g of Met/d, and urea + 15 g of Met/d. Cows were adapted to the experimental diet 30 d before the beginning of the study, with periods lasting for 14 d; 4 d to allow for clearance of the previous treatment effects, 4 d for adaptation to the treatments, and 6 d for total fecal and urine collection. Blood samples were collected every 4 h on d 13 of each period for analysis of serum metabolites and plasma AA. Inclusion of urea increased DM and OM intakes (urea vs. no urea; P = 0.05), but no further improvement in intake was observed with inclusion of Met. Serum urea concentrations increased with inclusion of urea (P = 0.03) and responded quadratically (P = 0.06) when Met was added, with the lowest concentration observed in the urea + 5 g of Met/d treatment. More N was retained with the inclusion of urea (P = 0.04), and N retention increased linearly (P = 0.07) with inclusion of Met. Plasma Met concentration increased linearly (P < 0.01) with inclusion of Met. These data suggest that Met was a limiting AA and that supplementation of a combination of urea and 5 g/d of rumen-protected Met to low quality, forage diets will improve N retention and promote protein accretion during late pregnancy.     

Effects of rumen-protected methionine and lysine on ruminant performance and nutrient metabolism

Four trials were conducted to determine the effects of supplemental rumen-protected methionine (RPMet) and lysine (RPLys) on lamb N metabolism and steer feedlot performance. In trial 1, 20 Suffolk-sired, crossbred lambs (avg weight 32 kg) were fed diets containing no supplemental methionine (Met) and lysine (Lys), .03% RPMet, .05% RPLys or .03% RPMet + .05% RPLys. Lambs fed .03% RPMet + .05% RPLys had a 33% increase in N retention compared with lambs fed no supplemental Met and Lys. In trial 2, to verify the protection and availability of these amino acids, five Targhee lambs (avg weight 35 kg) were fed corn-soybran flake diets supplemented with urea and were assigned in a 5 X 5 Latin square to one of the following treatments: 1) control; 2) .03% RPMet + .05% RPLys offered in the diet; 3) .03% RPMet + .05% RPLys abomassally infused; 4) .03% non-protected Met + .05% non-protected Lys offered in the diet and 5) .03% Met + .05% Lys abomasally infused. Treatments 2, 3 and 5 decreased (P less than .05) urinary N (g/d) and increased N retention (P less than .05) compared with the control diet (treatment 1). Increases (P less than .05) in plasma Met and Lys concentrations indicated that the amino acids were protected and available for animals at the site of absorption. In trial 3, 40 crossbred Angus steers (avg weight 247 kg) were fed diets composed of 53% corn silage and 47% concentrate and supplemented with soybean meal to 11.3% crude protein. Steers that were fed diets containing .19% RPMet + .11% RPLys had greater daily gain (P less than .05) than those fed diets containing no supplemental amino acids, .11% RPMet + .01% RPLys, and .15% RPMet + .06% RPLys (1.39 vs 1.23, 1.22 and 1.20 kg/d, respectively). Similar improvements in feed conversion resulted and increases in plasma Met concentrations followed the same trend. In trial 4, 40 crossbred Angus steers (avg weight 368 kg) were fed corn grain-corn silage diets supplemented with urea. Treatments were: no supplemental amino acids; .05% RPMet + .01% RPLys; .10% RPMet + .04% RPLys; and .15% RPMet + .07% RPLys. No differences in steer performance resulted due to supplemental RPMet and RPLys (P greater than .05). The results of these trials suggest that the RPMet and RPLys used in this study are protected from ruminal degradation, are available post-ruminally and can improve lamb N balance and growing steer performance.     

Effects of energy level on methionine utilization by growing steers

We evaluated the effect of energy supplementation on Met use in growing steers. Six ruminally cannulated Holstein steers (228 +/- 8 kg of BW) were used in a 6 x 6 Latin square and fed 2.8 kg of DM/d of a diet based on soybean hulls. Treatments were abomasal infusion of 2 amounts of Met (0 or 3 g/d) and supplementation with 3 amounts of energy (0, 1.3, or 2.6 Mcal of GE/d) in a 2 x 3 factorial arrangement. The 1.3 Mcal/d treatment was supplied through ruminal infusion of 90 g/d of acetate, 90 g/d of propionate, and 30 g/d of butyrate, and abomasal infusion of 30 g/d of glucose and 30 g/d of fat. The 2.6 Mcal/d treatment supplied twice these amounts. All steers received basal infusions of 400 g/d of acetate into the rumen and a mixture (125 g/d) containing all essential AA except Met into the abomasum. No interactions between Met and energy levels were observed. Nitrogen balance was increased (P < 0.05) by Met supplementation from 23.6 to 27.8 g/d, indicating that protein deposition was limited by Met. Nitrogen retention increased linearly (P < 0.05) from 23.6 to 27.7 g/d with increased energy supply. Increased energy supply also linearly reduced (P < 0.05) urinary N excretion from 44.6 to 39.7 g/d and reduced plasma urea concentrations from 2.8 to 2.1 mM. Total tract apparent OM and NDF digestibilities were reduced linearly (P < 0.05) by energy supplementation, from 78.2 and 78.7% to 74.3 and 74.5%, respectively. Whole-body protein synthesis and degradation were not affected significantly by energy supplementation. Energy supplementation linearly increased (P < 0.05) serum IGF-I from 694 to 818 ng/mL and quadratically increased (P < 0.05) serum insulin (0.38, 0.47, and 0.42 ng/mL for 0, 1.3, and 2.6 Mcal/d, respectively). In growing steers, N retention was improved by energy supplementation, even when Met limited protein deposition, suggesting that energy supplementation affects the efficiency of AA use.     

赖氨酸、蛋氨酸和苏氨酸对犊牛生长性能和血清生化指标的影响

本试验旨在研究赖氨酸、蛋氨酸和苏氨酸对犊牛生长性能和血清生化指标的影响.选取24头新生荷斯坦犊牛进行8周饲养试验,按照体重和出生时间相近原则分为4组,采用4种氨基酸模式的代乳粉,分别为氨基酸平衡组(PC组)、扣除赖氨酸组(PC-Lys组)、扣除蛋氨酸组(PC-Met组)、扣除苏氨酸组(PC-Thr组),扣除量均为对照组...     

Effects of rumen-protected methionine supplementation and bacterial lipopolysaccharide infusion on nitrogen metabolism and hormonal responses of growing beef steers

Metabolic demand for sulfur-containing AA increases during inflammation in nonruminants. Therefore, Met supplementation may alleviate the negative effects of infection on N balance. Effects of gram-negative bacterial lipopolysaccharide (LPS) and supplemental dietary Met on N balance, serum hormones and haptoglobin, and plasma urea-N and AA were evaluated in 20 Angus-cross steers (BW = 262 +/- 6.3 kg). Treatments (2 x 2 factorial) were infusion of no LPS (-LPS) or a prolonged low dose of LPS (+LPS) and dietary supplementation of no (-MET) or 14 g/d (+MET) of rumen-protected Met (providing 7.9 g/d of dl-Met). Steers were adapted to a roughage-based diet (DMI = 1.4% of BW daily) and supplemental Met for 14 d, and were then infused (1 mL/min via intravenous catheter) with LPS on d 1 (2 microg/kg of BW) and 3 (1 microg/kg of BW) of a 5-d collection period. Blood was collected on d 1, before LPS infusion, and at 2, 4, 6, 8, 10, 12, and 24 h after LPS challenge. Diet samples, feed refusals, feces, and urine were collected daily for 5 d. Rectal temperature and serum concentrations of cortisol, prolactin, tumor necrosis factor-alpha, and haptoglobin increased, whereas thyroxine and triiodothyronine decreased for +LPS vs. -LPS steers (LPS x h; P < 0.01). Plasma urea-N was greater for +LPS than -LPS steers (LPS; P = 0.03), and serum IGF-1 was not affected (P > or = 0.26) by LPS or Met. Plasma concentrations of Thr, Lys, Leu, Ile, Phe, Trp, Asn, Glu, and Orn decreased, plasma Ala increased, and Gly and Ser initially increased, then declined in +LPS vs. -LPS steers (LPS x h; P < or = 0.04). Plasma Met was greater for +MET than -MET steers before LPS infusion, but declined in +MET steers after LPS infusion (LPS x Met x h; P < 0.01). By design, DMI was not different, but DM digested was less (P = 0.04) for +LPS than -LPS steers. Infusion of LPS did not affect (P > or = 0.24) N intake, fecal N excretion, or N digested, but resulted in greater (P < 0.01) urinary N excretion and less (P < 0.01) N retention. The absence of an LPS x Met interaction (P = 0.26) for N retention indicates that supplemental Met does not improve the N utilization of growing beef steers exposed to a gram-negative bacterial endotoxin. Decreases in plasma concentrations of several essential AA in +LPS steers suggest that metabolic demand for these AA likely increased in steers exposed to endotoxin.