Effect of modified dry period lengths and bovine somatotropin on yield and composition of milk from dairy cows

Dry periods of 40 to 60 d have been an industry standard because dry periods <40 d have resulted in reduced milk yields in the subsequent lactation by 10 to 30%. However, recent research has demonstrated no production losses for cows given a 30-d dry period. The current study evaluated milk production effects of shortened or omitted dry periods for cows at mature-equivalent production >12,000 kg of milk and treated with bovine somatotropin (bST). The study used 2 commercial dairies and one university dairy and included 4 treatments. Five multiparous and 5 primiparous cows from each farm were assigned to each treatment: 1) 60-d dry period, label use of bST (60DD); 2) 30-d dry period, label use of bST (30DD); 3) continuous milking, label use of bST (CMLST); and 4) continuous milking with continuous use of bST (CMCST). Per label, bST use started at 57 to 70 d in milk and ended 14 d before drying (60DD and 30DD) or expected calving date (CMLST). In primiparous cows, average milk yields during the first 17 wk of lactation were reduced for cows on treatments 30DD, CMLST, and CMCST vs. the 60DD treatment. (38.3, 35.1, and 37.5 vs. 44.1 +/- 1.3 kg/d, respectively). For multiparous cows, respective milk yields did not differ (46.6, 43.4, 46.5, and 47.7 +/- 2.1 kg/d). Shortened or omitted dry periods may impede mammary growth in primiparous cows, resulting in reduced milk yield in the subsequent lactation. In contrast, a shortened or omitted dry period with either bST protocol did not alter production in multiparous cows treated with bST. Quality aspects of prepartum milk and colostrum require additional characterization. For multiparous cows, milk income generated for short dry periods or for continuous milking might increase their profitability. At 17 wk of the subsequent lactation, estimates of the cumulative net margins of multiparous cows on the 30DD treatment and continuous milking treatments exceeded those of cows on the 60DD treatment by 40 dollars to 60 dollars per cow.     

High levels of the mitochondrial large ribosomal subunit protein 40 prevent loss of mitochondrial DNA in null mmf1 Saccharomyces cerevisiae cells

Members of the YERO57c/YJGFc/UK114 protein family have been identified in bacteria and eukaryotes. The budding yeast Saccharomyces cerevisiae contains two different proteins of this family, Hmf1p and Mmf1p. We have previously shown that Mmf1p is a mitochondrial protein functionally related to its human homologue and able to influence the maintenance of mitochondrial DNA. Deletion of Mmf1 results in loss of the mitochondrial genome. Using a multicopy suppression approach, we have identified a protein of the mitochondrial large ribosomal subunit, MRPL40, which stabilizes mtDNA in Deltammf1 cells. Overexpression of MRPL40 did not prevent loss of mtDNA in a mutant strain lacking the mitochondrial protein Abf2p. Thus, MRPL40 does not have a general effect on mtDNA stability, but it may be specific for the mmf1-null strain. We also show that the Deltamrpl40 cells present a similar phenotype to the mmf1-null strain, having reduced mtDNA stability and growth rate. Furthermore, we observed that rho(+)Deltamrpl40 haploid cells can be obtained when tetrads are directly dissected on medium containing a non-fermentable carbon source. Thus, replication and segregation of the mtDNA can occur in the absence of MRPL40. We also show that another mitochondrial ribosomal protein, MRPL38, is able to overcome the Deltammf1-associated defect. Together, our results suggest a link between Mmf1p and the two mitochondrial ribosomal proteins.     

响应面法优化罗非鱼干制汤汁速酿鱼露工艺

以罗非鱼干制余留的鱼汤为主要原料,采用快速发酵法研究其鱼露发酵工艺,并按响应面试验设计方法优化其发酵工艺。结果表明,最佳发酵工艺条件为发酵温度42 ℃、加盐量10%、大豆固体曲添加量22%、还原糖添加量3%（木糖∶葡萄糖=1∶4）、料液比1∶1（g∶mL）、发酵时间9 d,最优工艺条件下所得样品中氨基酸态氮含量为0.763 g/100 mL。     

麸曲酱香白酒自动化通风制曲技术的应用及工艺总结

针对目前麸曲酱香白酒麸曲生产过程中存在的问题,对曲房和通风池进行改善,实现自动控温、控湿,对白曲、酵母、细菌的自动化通风制曲工艺进行了总结。改善后,白曲糖化力由500 mg/(g·h)提高到了700 mg/(g·h),酵母曲菌数由107 CFU/g曲提高到了109 CFU/g曲,细菌曲糖化力由120 mg/(g·h)提高到了200 mg/(g·h),液化力由原来的1.7 g/(g·h)提高到了4.5 g/(g·h)。     

微波真空干燥辅助不同方法提取红油香椿嫩芽挥发性成分的分析比较

为了分析不同方法提取香椿挥发性成分的差异,采用顶空固相微萃取法（HS-SPME）、超临界二氧化碳法（SFE-CO2）、超声波辅助乙醚法（UWE）提取真空微波干燥处理后的香椿挥发性风味物质,并利用GC-MS对提取的样品进行检测、分析及鉴定。结果表明,顶空固相微萃取法共检测出71种风味物质,主要为烯类、酮类与醇类;超临界二氧化碳法检测出56种风味物质,主要为烯类、醛类与醇类;超声波辅助乙醚法可检测出68种风味物质,主要为烯类。HS-SPME法检测的醛类、含硫类、酮类、醇类、酯类、烃类等相对含量最高,UWE法检测的烯类相对含量最高。HS-SPME法还检测出其它两种方法未检测到的含硫类物质——二丙烯基硫醚和叔十六硫醇,这些物质与其它化合物共同赋予了香椿独特的风味。三种方法在提取香椿挥发性化合物种类、组分、相对含量存在差异,HS-SPME法能最大程度的提取香椿挥发性成分,较真实、全面的反映香椿香气特征。      

超声-微波协同酶法改性小米糠膳食纤维及工艺优化

为提高小米糠水溶性膳食纤维（Soluble dietary fiber,SDF）的得率,本实验以小米糠为材料,对其进行气爆预处理,利用超声-微波协同酶法对气爆预处理小米糠进行改性,分别研究酶添加量、温度、pH、微波功率对小米糠SDF含量的影响,根据单因素实验结果设计Box-Behnken实验,采用响应面法优化改性小米糠SDF的工艺条件。结果表明:气爆条件设定为压力1.0 MPa、时间90 s,最优工艺参数为酶添加量5.85%,温度56℃,pH4.64,微波功率451 W,在此条件下改性小米糠SDF含量为13.117%,比未经改性小米糠SDF含量高出了10.96%。      

苯甲酸降解菌的分离鉴定及其对烤烟幼苗生长的影响

为降低烟草连作对烟叶产量和品质以及烟草生长发育带来的不良影响,通过平板筛选和摇床复筛,从烤烟根系分泌物中筛选出一株能高效降解苯甲酸的菌株。结果表明,根据rDNA-ITS的扩增及序列分析、培养特征及形态特征观察初步鉴定该菌株为黄曲霉(Aspergillus flavus);该菌株培养15 d内,在0~800 μmol/L苯甲酸浓度范围内能够正常生长,800~1600 μmol/L苯甲酸浓度范围内生长受到一定程度抑制;该降解菌在以苯甲酸为唯一碳源的800 μmol/L浓度LBA培养基中菌株干重、降解率均达到最大,菌株干重为0.765 g,降解率为19.98%;菌株在培养至第9天时降解速率达到最快,为8.5 mg/d;烤烟幼苗生长过程中施加降解菌液能在一定程度上降低根系分泌物的抑制作用。该降解菌株在盆栽试验中能够降低根系分泌物对烤烟的自毒作用,使微生物菌株降解烤烟自毒物质来克服连作障碍成为可能。     

助剂配送系统在长车印染企业的改造应用

为提高助剂配送系统在长车印染企业的生产稳定性,在传统助剂配送系统结构的基础上,提出了输送动力改造方案及"一用一备"加料缸设计。同时针对不同助剂提出不同的输送技术方案。实际使用效果表明,通过以上改造,助剂配送系统可充分满足长车生产过程中的助剂加料需求。     

基于主成分分析的玉米DDGS物理特性评价

为对玉米DDGS的物理特性进行分析及量化评价,以国内外8个玉米DDGS为试验材料,测定分析其容重、热物理特性、摩擦特性、粉碎特性及色差指标参数,并运用主成分分析法简化物理特性指标,构架评价体系,得到每种样品的综合得分。结果表明:样品各物理特性指标间存在不同程度的差异;各物理特性指标之间存在不同程度的相关性,比热与热导率呈极显著正相关,与导温系数呈极显著负相关;热导率与平均粒径呈显著正相关;导温系数与容重呈极显著负相关;摩擦系数与休止角呈极显著正相关,与平均粒径呈极显著负相关;L*、b*与平均粒径呈极显著正相关;L*与b*呈极显著正相关。通过主成分分析提取了3个主成分,累积方差贡献率达到87.415%;主成分分析的结果表明进口玉米DDGS的物理特性较好。     

莱茵-埃农氏法和高效液相色谱-示差折光法检测奶粉中乳糖和蔗糖的比较研究

选用市售同种品牌不同年龄段的奶粉,采用莱茵-埃农氏法和高效液相色谱-示差折光检测法对其乳糖和蔗糖进行测定,分析乳糖和蔗糖的差异,并对两种分析方法的结果进行比较,为奶粉中乳糖和蔗糖的检测方法提供依据。结果表明,莱茵-埃农氏法和高效液相色谱-示差折光检测法相比,高效液相色谱-示差折光检测法测定乳糖和蔗糖含量的准确度更高,蔗糖和乳糖的线性范围均为2～12 mg/mL,相关系数分别为0.999 3、0.999 6,精密度实验结果表明,相对标准偏差分别为2.53%、3.81%,平均加样回收率分别为99.70%、101.06%。高效液相色谱-示差折光检测法结果准确、分析时间短、前处理简单,适用于快速测定奶粉中蔗糖和乳糖含量。