Pasture and forage crop systems for non-irrigated dairy farms in southern Australia. 2. Inter-annual variation in forage supply,and business risk     

D.F. Chapman  S.N. Kenny  D. Beca  I.R. Johnson 《Agricultural Systems》2008

Inter-annual climatic variability poses a substantial management and profitability challenge for pasture-based dairy producers in southern Australia. The effects of a range of seasonal scenarios on the production and profit of non-irrigated dairy farm systems using several different forage bases were investigated for two regions in southeast Australia using a systems modeling approach. For the Terang district, seasonal scenarios were constructed around combinations of early, average or late autumn rains, and short, average or long spring flushes. For the higher-rainfall Ellinbank district, scenarios were constructed around either above- or below-average summer–autumns or winter–springs.  相似文献   

Comparison of two pasture growth models of differing complexity     

R. Howard Skinner  Michael S. Corson  C. Alan Rotz 《Agricultural Systems》2008

Two pasture growth models that shared many common features but differed in model complexity were refined for incorporation into the Integrated Farm System Model (IFSM), a whole-farm model that predicts effects of weather and management on hydrology, soil nutrient dynamics, forage and crop yields, milk or beef production, and farm economics. Major differences between models included the explicit representation of roots in the more complex model and their effects on carbon partitioning and growth. The simple model only simulated aboveground processes. The overall goal was to develop a model capable of representing forage growth and ecosystem carbon fluxes among multiple plant species in pastures while maintaining a relatively simple model structure that minimized the number of required user inputs. Models were compared to observed yield data for 12 site-years from three experiments in central Pennsylvania, USA. Both models underestimated observed yield by 6% when averaged across site-years. However, the simple model provided a better fit to the one-to-one line between observed and simulated yield than did the complex model. The models also showed similar relationships between yield and gross primary productivity (GPP), despite the fact that the complex model was specifically developed to optimize simulation of GPP. The simple model predicted much greater shoot respiration and carbon partitioning to above ground plant tissues, but less shoot senescence than the complex model. Published data on the proportion of GPP consumed in aboveground or total plant respiration exhibit a wide range of values, making it impossible to determine which model provided the best representation of respiration rates and, thus, of the entire carbon budget.  相似文献   

草鱼的低盐-高水分冷冻半干制品耐藏性研究   总被引：1，自引：0，他引：1  

吴平华  殷俊峰 《安徽农业科学》2008,36(26)

[目的]探讨草鱼加工成低盐-高水分冷冻半干制品的可适性及其耐藏性。[方法]通过腌制、干燥、包装、速冻和冻藏将市售新鲜的草鱼加工成低盐-高水分冷冻半干制品,研究冻藏过程中鱼体水分含量、盐分含量、系水力和其感官品质的变化。[结果]相对于擦干鱼体对照组,腌制、干燥后的试验组鱼体失水更慢,系水力下降较慢。随着冻藏时间的延长,2组鱼体的感官品质均下降,但试验组鱼体的下降速度更慢。冻藏过程中,2组鱼体的盐分含量变化较小,但对照组鱼体的盐分含量有缓慢上升趋势。[结论]草鱼较适合制成低盐-高水分冷冻半干制品,耐藏性较好,且在盐渍和干燥过程中增加了制品的风味,具有较好的口感。  相似文献   

外源酶对草鱼鱼种生长及饲料表观消化率的影响     

黄峰  施培松  文华  魏开建  严安生 《安徽农业科学》2008,36(3):1057-1059,1125

[目的]探讨酶制剂在水产动物饲料中得到合理利用的途径。[方法]在饲料中添加木聚糖酶(01、503、00 mg/kg),N-蛋白酶(0、50、100 mg/kg)、淀粉酶(02、004、00 mg/kg)和纤维素酶(02、004、00 mg/kg)4种单体纯酶,并采用L9(34)正交设计法,将4种单体酶配制成复合酶制剂,研究外源酶制剂对草鱼鱼种的生长及饲料表观消化率的影响。[结果]4种单体酶对草鱼鱼种生长影响的主次顺序为木聚糖酶>淀粉酶>N-蛋白酶>纤维素酶;外源复合酶对饲料干物质和粗蛋白表观消化率有一定的影响,且影响力大小依次为木聚糖酶>纤维素酶>淀粉酶>N-蛋白酶。外源复合酶的适宜配方为:木聚糖酶300 mg/kg、淀粉酶200~400 mg/kg、N-蛋白酶0~50 mg/kg和纤维素酶0~200 mg/kg。[结论]饲料中添加外源复合酶可提高草鱼的特定生长率和增重率,提高草鱼对饲料的消化率。  相似文献   

休牧对云南退化山地草甸草群结构的影响   总被引：3，自引：1，他引：2  

殷振华  毕玉芬  李世玉 《草地学报》2008,16(6):630-635

为探明休牧对云南退化山地草甸的恢复和改良作用,对3年休牧封育进行监测。结果表明:休牧封育对恢复退化山地草甸植被有明显的效果;休牧封育后植株的高度明显提高;封育3年,轻、中和重度退化草地的草层高度分别较对照区提高了7、16和16倍;封育后群落组成发生显著变化,禾本科牧草比例上升,杂类草明显下降;封育提高了草地群落优良牧草的比率;封育3年即可恢复草地;封育是恢复退化山地草甸的一项有利于畜牧业可持续发展的良好措施。  相似文献   

草鱼肠道胰蛋白酶同工酶GT-A的动力学和热力学性质     

刘忠义 《西北农林科技大学学报(自然科学版)》2008,36(1):211-217

【目的】研究草鱼肠道胰蛋白酶的化学组成和酶学性质,以便深入了解该酶的特性并探讨其工业应用潜力。【方法】用生物化学方法结合仪器分析,测定了草鱼消化道胰蛋白酶同工酶GT-A的氨基酸组成,分析了其动力学和热力学性质。【结果】GT-A的最大反应速度(Vmax)和米氏常数(Km)值分别为2 000 min-1和21.21μmol,生理转化效率(Vmax/Km)较高,为94.3 min-1.μmol-1;其Arrhenius活化能很低,为17.22 kJ/mol。差示扫描量热分析(DSC)表明,其热变性温度为66.3℃,Ca2+的存在可将该酶的热变性温度提高到73.0℃。氨基酸分析表明,草鱼胰蛋白酶GT-A的芳香族氨基酸含量很低,形成二硫键的潜力极低。紫外扫描发现,GT-A在205 nm附近有最大紫外吸收,而在280 nm附近的吸收很微弱。【结论】GT-A具有冷水性鱼消化蛋白酶的部分特性,且其生理转化效率高而活化能低,具有很好的利用前景。  相似文献   

基于能值分析的蜜柚园生草模式生态经济效益评价   总被引：2，自引：2，他引：0  

罗旭辉  卢新坤  刘岑薇  张丽君  陈恩  Gordon W. Price  翁伯琦 《中国生态农业学报》2019,27(12):1916-1924

蜜柚是福建省平和县优势特色产业,目前面临发展困境。生草栽培是推动蜜柚绿色发展的重要途径,为科学评价蜜柚园生草模式的生态经济效益,本文应用能值分析法测评平和县五寨镇前岭村蜜柚园生草模式和蜜柚园清耕模式的能值自给率、能值投资率、净能值产出率、环境负载率、有效能产出率和能值反馈率。结果表明：2017-2018年蜜柚园生草模式、蜜柚园清耕模式的能值自给率均为0.003,能值投资率分别为339.291、295.763,净能值产出率均为1.003,环境负载率分别为0.348、0.321,有效能产出率为4.57E-7 J·sej^-1、2.90E-7 J·sej^-1,能值反馈率为0.002、0.000。与清耕模式相比,生草模式能值总投入下降9.21%,不可更新环境资源下降76.71%,购买能值比重大,显示更高的能值投资率;同时商品果能值提高1.00E+17 sej·hm^-2,能量产出提高4.60E+10 J·hm^-2,表现出更强的经济活力。劳动力能值投入占能值总投入70.45%~72.90%,其中采摘、日常管理、水肥施用比重大。生草模式在除草环节增加劳动力投入1.31E+16 sej·hm^-2,但通过减少农药施用、水肥施用和有机肥搬运节约劳动力,同时优化日常管理,生草模式总劳动力投入降低了3.30E+16 sej·hm^-2,基于能值的劳动生产率提高17.50%。生草模式使有机肥、劳动力等可更新资源购买量减少,环境负载率增加0.027。蜜柚园生草模式实现了柚树增产、柚农增收、蜜柚园增绿,为蜜柚产业供给侧结构性改革提供赋能路径。  相似文献   

新疆沙尔套山天然草地主要混合牧草营养指标近红外光谱分析     

张凡凡  尉小霞  段宏伟  于磊  张文举 《草地学报》2019,27(3):661-667

为了对新疆沙尔套山天然草地主要牧草营养指标进行快速、无损检测,本试验采用近红外光谱技术（Near infrared reflectance spectroscopy,NIRS）,进行修正偏最小二乘回归法（Modified partial least squares,MPLS）,结合散射处理、导数、平滑等不同的光谱预处理和数学处理方法,建立了32种主要牧草（草粉）的粗蛋白（Crude protein,CP）、中性洗涤纤维（Neutral detergent fiber,NDF）、酸性洗涤纤维（Acid detergent fiber,ADF）、粗灰分（Ash）、钙（Ca）和磷（P）的校正模型。结果表明：CP、NDF、ADF、Ash、Ca和P的交叉检验决定系数（R²）分别为0.82,0.80,0.78,0.50,0.72和0.65,交叉验证标准误差（Standard error of cross validation,SECV）分别为2.36,6.17,3.87,0.85,0.24和0.07,交叉验证相对分析误差（Relative percent deviation of cross validation,RPDCV）分别为2.78,2.26,2.39,1.92,2.39和1.65。最后结合外部验证集对各矫正模型进行验证。试验得出CP、NDF、ADF外部验证相对分析误差分别为2.67,2.20和2.28,相关性分别为0.66,0.73和0.84,其模型精确度和验证准确度还有待提高;利用近红外光谱检测技术不能建立Ash、Ca和P的检测模型。  相似文献   

草鱼BPI/LBP基因的克隆及特征研究     

杨春荣  苏建国  黄腾 《西北农林科技大学学报(自然科学版)》2011,39(8):8-14

【目的】克隆草鱼杀菌通透性增加蛋白/脂多糖结合蛋白（Bactericidal permeability-increasing protein/LPSbinding protein,BPI/LBP）基因的cDNA全长,分析其结构特征,研究其表达规律,为进一步探明其功能奠定基础。【方法】首先用同源克隆及快速扩增cDNA末端技术(RACE),克隆草鱼BPI/LBP基因的cDNA全长,然后用生物信息学方法分析BPI/LBP基因的结构特征,最后用半定量RT-PCR检测BPI/LBP基因在草鱼不同组织（血、脑、眼睛、前肠、中肠、后肠、鳔、鳃、头肾、中肾、心脏、肝胰脏、肌肉、皮肤和脾脏）中的表达模式。【结果】草鱼BPI/LBP cDNA全长1 568 bp,编码473个氨基酸,其中包括18个氨基酸组成的信号肽、BPI1结构域（BPI/LBP/CETP N-terminal domain）和BPI2结构域（BPI/LBP/CETP C-terminal domain）。该蛋白的分子质量为51 551 u,等电点为8.69。氨基酸序列同源性分析结果显示,草鱼与鲤鱼BPI/LBP的同源性最高（90%）,其次为虹鳟（73%）、斑点叉尾鮰（73%）、香鱼（72%）等。在系统进化树中,草鱼BPI/LBP首先与鲤科的鲤鱼聚为一类。通过半定量RT-PCR分析可知,草鱼BPI/LBP基因在被检测的15个组织中都有表达,其中在鳃中的表达量最高,其次为头肾、中肾等。【结论】成功克隆了草鱼BPI/LBP基因的cDNA全长,该基因在草鱼体内不同组织中广泛表达。  相似文献   

Evaluation of post-emergence herbicides for the control of wild oat (Avena fatua L.) in wheat and barley in Argentina     

J.A. ScursoniMaría P. Catanzaro  Julieta QuirogaFlorencia Goldar 《Crop Protection》2011,30(1):18-23

Wild oat (Avena fatua L.) is the most troublesome weed in cereal crops in Argentina. With the aim of studying the effects of different herbicides, doses, and wild oat growth stage at application on weed control and crop yield, field experiments were conducted in wheat and barley crops during three growing seasons in the south of Buenos Aires Province, Argentina. Treatments were post-emergence applications of new herbicide, pinoxaden + cloquintocet mexyl (5%-1.25%), at doses that ranged from 20 g to 60 g a.i. pinoxaden ha⁻¹, applied at two to three leaves and the beginning of tillering of wild oat. In addition, standard treatments were included and applied at the same wild oat growth stages. Diclofop methyl at 511 g a.i. ha⁻¹ and fenoxaprop-p-ethyl at 55 g a.i. ha⁻¹ were applied in barley. In wheat, diclofop methyl was replaced by clodinafop-propargyl + cloquintocet mexyl (24%-6%) at 36 g a.i. clodinafop-propargyl + 9 g cloquintocet mexyl ha⁻¹ and in 2008/09 wheat experiments, iodosulfuron plus metsulfuron methyl (5%-60%) at 3.75 g a.i. ha⁻¹ + 3 g a.i. ha⁻¹ also was included. In both crops, pinoxaden at 30 g a.i. ha⁻¹ and at higher rates, fenoxaprop-p-ethyl and clodinafop-propargyl gave the best control of wild oat. In 2006/07 wheat crops, treatments applied at tiller initiation provided better control than the early timing averaged across herbicides. However, wheat yield generally was greater with early application. In barley, wild oat control and crop yield were similar regarding time of application. Variations in crop yield were correlated with grain number m⁻² both in wheat and barley, but relationships between both grain number and spikes m⁻² and with grains per spike were identified only in wheat.  相似文献