氨基酸与母猪营养

母猪饲养是养猪生产中最重要的环节之一。母猪的营养尤其是蛋白质和氨基酸营养不仅直接影响仔猪的生长性能,而且也对母猪的使用年限和繁殖性能会产生很大影响。母猪蛋白质及氨基酸营养受品种、胎次、母猪体况、产仔数、泌乳量、采食量、哺乳期长短等诸多因素影响,增大了母猪氨基酸营养的研究难度。同时母猪个体较大、研究成本高、试验群体偏小、数据采集困难以及试验误差较大等问题也限制了母猪蛋白质及氨基酸营养的系统研究。本文对母猪的氨基酸营养进行综述,旨在为养猪生产实践中母猪日粮的合理配制提供参考。     

支链氨基酸对泌乳母猪的营养研究进展

支链氨基酸 (BCAA)是畜禽的必需氨基酸 ,有着重要的营养生理作用 ,对泌乳母猪尤其显著。本文着重阐述BCAA　　对泌乳母猪生产性能方面的影响 ,泌乳母猪对BCAA的需要量及缬氨酸需要量研究模式。     

添加缬氨酸和异亮氨酸对哺乳母猪及其仔猪生产性能的影响

本试验旨在探讨在哺乳母猪日粮中添加缬氨酸和异亮氨酸对母猪及其仔猪生产性能、母猪采食量和乳成分的影响.试验选用健康、体况、预产期相近的第2胎法系JALAX母猪144头,分成3个处理组,即对照组、试验A组和试验B组,每个处理48头母猪.对照组饲喂基础日粮,试验A组饲喂添加低水平支链氨基酸日粮(基础日粮 缬氨酸0.26% 异亮氨酸0.06%),试验B组饲喂添加高水平支链氨基酸日粮(基础日粮 缬氨酸0.36% 异亮氨酸0.14%).试验从母猪妊娠108 d进产房开始,到仔猪21日龄断奶时结束.试验结果表明:(1)添加缬氨酸和异亮氨酸提高了仔猪的断奶窝重、断奶窝增重、平均日增重和21日龄仔猪成活率,但以试验A组的效果较好,和对照组比,上述指标分别提高了23.10%(P<0.01)、30.45%(P<0.01)、19.26%(P<0.05)和7.16%(P<0.05);(2)添加缬氨酸和异亮氨酸提高了哺乳母猪哺乳11～15 d,16～21 d以及哺乳全期的采食量,试验A组比对照组分别提高了35.61%(P<0.01)、27.72%(P<0.01)和24.21%(P<0.01),试验B组虽然与对照组之间差异不显著(P>0.05),但有提高的趋势;(3)添加缬氨酸和异亮氨酸极显著提高了泌乳第1天、第7天和第15天乳中乳脂、乳蛋白、总固形物、非乳脂固体的含量(P<0.01),极显著降低了乳糖的含量(P<0.01),但以试验A组的效果最好;(4)添加缬氨酸和异亮氨酸极显著提高了初乳(泌乳第1天)的总必需氨基酸、总非必需氨基酸以及总氨基酸的含量(P<0.01),但对第7天和第15天乳中氨基酸含量影响不显著.因此,日粮中添加缬氨酸和异亮氨酸可以提高哺乳母猪的日采食量和改善母猪乳品质,从而提高哺乳仔猪的生长性能.     

Properties of acetolactate synthase from sulfonylurea-resistant Scirpus juncoides Roxb. var. ohwianus T. Koyama

Properties of acetolactate synthase (EC 4.1.3.18; ALS) from sulfonylurea-resistant (SUR) Scirpus juncoides Roxb. var. ohwianus T. Koyama were studied biochemically and physiologically in comparison with those from sulfonylurea-susceptible weed (SUS). GR₅₀ values for growth inhibition and I₅₀ values for ALS inhibition by imazosulfuron were determined for both SUR and SUS. Imazosulfuron controlled the SUS above 80% at the dosage more than 10 g a.i./ha but did not control the SUR at the even great dosage of 1000 g a.i./ha. The rates required for 50% growth inhibition of the SUR relative to the SUS (R/S ratio) were 271-fold. The I₅₀ value for inhibition of ALS from the SUS was 15 nM, compared to I₅₀ of >3000 nM for inhibition of ALS from the SUR. These results suggest that a resistance may due to an altered ALS that is insensitive to imazosulfuron. The K_m (pyruvate) value of ALS from the SUR was similar to the K_m for ALS from the SUS, suggesting that a mutation resulting in resistance does not change the affinity of the enzyme for pyruvate. The specific activity of the SUR ALS was similar to that of the SUS ALS, which indicates that resistance is not an over-expression of the enzyme. ALS activity from both biotypes was inhibited by isoleucine, valine, and leucine in this order. However, the SUR ALS was less sensitive to inhibition by valine than the SUS ALS.     

有关母猪缬氨酸的研究进展

缬氨酸是对母猪泌乳性能尤为重要的一种支链氨基酸,也对乳腺的生长发育具有极其重要的意义。缬氨酸具有改善母猪和仔猪生产性能,提高母猪乳汁质量,氧化供能,提高动物机体免疫力及调节动物体内蛋白质代谢等功能。本文综述了缬氨酸在母猪上的主要生理功能、缬氨酸与其他支链氨基酸的关系以及母猪氨基酸的限制顺序和母猪对缬氨酸的需要量。     

缬氨酸转氨酶工程菌的构建及表达条件的优化

[目的]构建缬氨酸转氨酶基因(avtA)的大肠杆菌工程菌,并优化其表达条件。[方法]将avtA基因插入到载体pET32a中,构建表达质粒pET32a-avtA,通过纸层析检测酶活性,SDS-PAGE凝胶电泳检测目的蛋白,并通过考察培养基中蛋白胨浓度、IPTG诱导浓度和诱导时间来优化其表达条件。[结果]成功构建了缬氨酸转氨酶基因的大肠杆菌工程菌,其最佳表达条件为:培养基中蛋白胨浓度为12g/L,IPTG浓度为0.4 mmol/L,诱导时间为8 h。[结论]缬氨酸转氨酶工程菌具有良好的应用前景。     

Multiple effects of a naturally occurring proline to threonine substitution within acetolactate synthase in two herbicide-resistant populations of Lactuca serriola

Two populations of Lactuca serriola L. with resistance to acetolactate synthase (ALS)-inhibiting herbicides were discovered in wheat fields at two locations more than 25 km apart in South Australia. Both resistant populations carried a single base change within a highly conserved coding region of the ALS gene that coded for a single amino acid modification within ALS. The modification of proline 197 to threonine resulted in an enzyme that was highly resistant (>200-fold) to inhibition by sulfonylurea herbicides and moderately resistant to triazolopyrimidine and imidazolinone herbicides. The herbicide-resistant ALS was also less sensitive to inhibition by the branched-chain amino acids valine and leucine. In addition, the resistant enzyme had a lower K_m for pyruvate. However, extractable ALS activity was similar between resistant and susceptible plants. The substitution of threonine for proline 197 within ALS has multiple impacts on ALS enzyme activity in L. serriola that may influence the frequency of this resistant allele in the environment.     

Dietary Valine Requirement of Fingerling Catla catla

A 12-week feeding trial was conducted to determine the dietary valine requirement of fingerling Catla catla (3.50 ± 0.15 cm, 0.63 ± 0.04 g). Seven casein gelatin-based diets (33% crude protein; 3.34 kcal/g digestible energy) containing graded levels of valine (0.51%, 0.69%, 0.91%, 1.12%, 1.31%, 1.49%, 1.71% dry diet) were fed to triplicate groups of fish to apparent satiation at 08:00, 12:30, and 17:30 h. Absolute weight gain (AWG), feed conversion ratio (FCR), specific growth rate (SGR%), protein efficiency ratio (PER), protein productive value (PPV), valine retention efficiency (VRE), valine gain (VG), energy retention efficiency (ERE), and carcass protein improved significantly (P < 0.05) with the increasing concentrations of dietary valine from 0.51% to 1.12%. Quadratic regression analysis of AWG, PPV, DPD, VG, ERE, and carcass protein at 95% maximum (Y_95%max) response against varying levels of dietary valine yielded the requirement at 1.04%, 1.03%, 1.05%, 1.04%, 1.01%, and 0.98% of dry diet, respectively. It is recommended that inclusion of valine at 1.02% of dry diet, corresponding to 3.09% of dietary protein, is optimum in formulating valine-balanced feeds for fingerling C. catla.     

草鱼幼鱼对缬氨酸需要量的研究

试验选用体重(9.5±0.3)g的草鱼幼鱼,随机分成6个组,每组3个重复,每个重复20尾;以花生仁粕、酪蛋白及明胶为蛋白质源,分别饲喂缬氨酸水平为7.3～22.3 g/kg的6组等氮半精制饲料(粗蛋白质含量为32%),经70 d的生长试验研究其日粮缬氨酸的最适需求量.试验结果表明:日粮缬氨酸水平对草幼鱼的增重率、特定生长率、蛋白质效率、肌肉RNA/DNA比率、鱼体常规成分组成、消化酶活性、肝胰脏谷草-谷丙转氨酶和谷氨酸脱氢酶活性以及血液学指标都有显著的影响(P<0.05).随日粮缬氨酸水平的增加,增重率,特定生长率、蛋白质效率及肌肉RNA/DNA比率均呈先升后降趋势,均在16.3 g/kg组达到最大值(P<0.05).以增重率、特定生长率、肌肉RNA/DNA比率为基础对饲料缬氨酸水平进行二次回归分析,确定草鱼幼鱼日粮(32%粗蛋白质)缬氨酸适宜需要量分别为15.6、15.1及16.0 g/kg(日粮基础)或48.8、47.2及50.0 g/kg(日粮蛋白质基础).     

亮氨酸和缬氨酸在绵羊骨骼肌和肾组织中的分解代谢

本研究测得5头15月龄体重33.5±2.5千克的美利奴羯羊血浆、骨骼肌和肾组织中游离分支氨基酸含量为:缬氨酸含量>亮氨酸含量)异亮氨酸含量。组织中游离分支氨基酸含量略高于血浆中含量。不同组织(骨骼肌和肾)中分支氨基酸转氨酶(EC 2.6.1.42)在作用底物(亮氨酸或缬氨酸)相同时的Km值相近似,但Vmax却呈现较大的差异。组织中游离亮氨酸和缬氨酸在不同含量水平下的转氨基分解量显著不同(P<0.01)。当组织中游离亮氨酸和缬氨酸含量在1.5～5倍于正常组织水平范围内变化时,分解量的增加幅度为0.5～3倍。实验结果初步表明,酶的活性诱导作用是绵羊组织中分支氨基酸代谢性拮抗作用机制之一。