Use of the Lachema Bio-La-Test for the determination of urea in milk

The content of urea in milk was studied as a parameter of dairy cow nutrition. It is possible to use for the analysis whole milk where the values are lower by 5.96% than in defatted milk (this fact must be borne in mind when the results are interpreted). Protein can be removed from whole milk within 24 hours after sampling provided that it was placed in a refrigerator within four hours from milking to be stored there at 4 degrees C. In such a case the decrease in urea level is not greater than 4%. No significant differences were found between urea concentration in milk collected by stripping and that in bulk milk. It is not recommended to take samples at the end of milking because such milk contains less urea. Urea concentration in the bulk milk samples corresponds to the average urea concentration in the milk samples taken from dairy cows in the stable.     

The role of conserved forages in the nutrition of the dairy cow

Forages are universally popular ingredients in dairy rations because of (1) their agronomic properties, (2) their economy as sources of energy and essential nutrients, and (3) their physiological role in digestion. The contribution that forages make in support of milk production is limited by the cow's capacity for feed intake, especially in early lactation. While varying greatly from cow to cow, feed intake is more highly correlated to daily milk yield in mid-lactation than earlier. Factors affecting intake of forage are discussed. Early harvesting in combination with proper conservation are shown to maximize the potential of forage for supporting milk production.The effects of forage quality and quantity in mixed diets are discussed in relation to rumen fermentation and milk yield response. It is emphasized that although liberal grain feeding is needed to attain high milk yield, restricted forage allowance may seriously affect milk yield and milk composition. It is concluded that the importance of forages generally declines compared to concentrates with increased milk production but that liberal feeding of high quality forages is needed to maintain normal digestion and high milk yield under practical farm conditions.     

内蒙古阿拉善盟双峰驼驼乳理化性质研究

本文研究了10峰内蒙古阿拉善盟双峰驼不同泌乳时间驼乳的一般理化性质。其比重及pH值与已有报道的单峰驼驼乳结果基本一致,而酸度(%)高于单峰驼。电导率与乳中Na+、K+和Cl-含量之和有关,随三者之和的增减而增减。驼乳的蛋白质、脂肪、乳糖、干物质、灰分和钙的含量均高于牛乳,磷的含量比牛乳略低。驼乳的缓冲性与牛乳有差异:当乳样先酸化后用碱回滴时,驼乳和牛乳分别在pH4.4～6.6和pH5.0～6.6范围内出现典型的“弧形线”,驼乳的最大缓冲作用发生在pH近似4.4处,牛乳的最大缓冲作用在pH近似5.1处,但驼乳在pH4.9处仍有一个缓冲峰。双峰驼驼乳的酒精稳定性(75±2.0)%稍低于牛乳的酒精稳定性(77±1.0)%,驼乳与牛乳的酒精稳定性的变化趋势基本一致,加入Na+、K+都引起酒精稳定性降低,游离Ca2+浓度的降低或pH值的上升都会导致酒精稳定性的增加。     

我国生鲜乳价格形成机制的剖析、问题及建议

生鲜乳价格形成机制是奶业利益联结机制的核心问题。本文重点围绕购销双方关系,从生鲜乳购销合同形式、生鲜乳指标检测、生鲜乳计价体系、生鲜乳交易结算方法等方面对我国生鲜乳价格形成机制进行剖析。在此基础上探讨当前生鲜乳价格形成机制中面临的价格形成基本由乳品企业制定、奶牛养殖场（户）寻求公平交易的诉求无处表达、生鲜乳协商价格的约束力不强、生鲜乳交易的监督机制有待完善等问题。提出了建立公平、公正、公开的生鲜乳价格形成机制,建立有制度保障的生鲜乳价格协商机制,探索“生鲜乳购销合同”协商机制,建立公开、透明的生鲜乳计价体系,建立生鲜乳第三方检测制度等5个方面的对策建议。     

饲粮组成对牛乳中乳蛋白及乳脂肪合成与调控机理影响的研究进展

牛乳中的营养物质对人类健康有着相当大的益处,乳蛋白和乳脂肪作为牛乳营养品质的物质基础,还与奶牛生产性能息息相关,受到人们的广泛关注。本文从牛乳中基本营养物质的种类和功能出发,重点介绍了饲粮组成的改变及添加植物提取物、微量元素、微生态制剂等对乳蛋白及乳脂肪合成与调控机理的影响,为科学合理地调整饲粮营养组成,提高牛乳中乳蛋白率和乳脂率提供理论依据。     

日粮组成对牛奶中乳成分合成与调控机制影响的研究

牛奶中乳蛋白和乳脂肪含量的高低直接关系到牛奶的品质和风味。牛奶中乳蛋白主要可以分为酪蛋白和乳清蛋白两种类型,其合成代谢过程均受到mTOR信号分子通路、JAK-STAT信号分子通路、GCN2-eIF2a信号分子通路的影响。牛奶中乳脂肪主要为三酰基甘油酯、磷脂等,对于牛奶的营养和风味均有重要影响,其受到脂肪酸相关酶ACACA、FAS、SCD1的调控。饲料营养是影响牛奶中乳蛋白和乳脂肪的关键因素之一,包括精粗饲料配比及饲料添加剂的应用等方面。本文对牛奶中乳蛋白和乳脂肪的合成调控机理,及日粮组成对其的影响机制进行阐述,为改善乳品质提供参考。     

乳的合成过程及其在生产中的应用技术

乳脂、乳蛋白和乳糖是牛奶中的主要营养成分，也是影响牛奶品质的主要因素，通过营养调控途径可以有效改善牛奶中的乳脂率、乳蛋白率和乳糖含量，本文阐述了牛奶中乳脂、乳蛋白和乳糖三大营养物质的合成过程、作用机理以及生产中的实践应用技术。     

牛奶风味影响因素的研究进展

牛奶风味的影响因素包括多个方面,其主要取决于复杂的风味活性物质。一些风味活性物质直接来源于奶牛的饲料成分,但有些风味活性物质的来源还不确定。介于风味活性物质的复杂性,一些相关的信息较少,主要有两个假设,一是来源于动物所采食的饲料成分,一是消化产物的衍生物。     

光诱导乳脂肪氧化的研究进展

脂肪是牛乳中重要的营养成分之一,其中的不饱和脂肪酸,尤其是多不饱和脂肪酸容易被氧化.随着市场上越来越多透明包装的出现,光诱导乳脂肪的氧化成为导致牛乳品质劣化及酸败的重要原因之一,这不仅影响牛乳风味,而且氧化产物对人类健康造成巨大威胁.本文综述乳脂肪光氧化的机理、主要影响因素及评价方法.为抑制乳制品光氧化、保证乳制品质量...     

OIE标准全乳iELISA与国标全乳环状试验在奶牛布鲁氏菌病检测中的研究

从不同地区采集奶样,将OIE诊断试验中用于牛布病诊断的全乳iELISA与国标中的MRT进行比对。在检测的526份样品中,全乳iELISA检出93份阳性,国内MRT抗原检出31份阳性,英国卫桥的MRT抗原检出44份阳性(检测数为264份);对其中一个地区的31份奶品,除了抗体的检测外,同时进行了奶样的细菌分离、奶样提取DNA的检测,全乳iELISA与乳样DNA提取均检出21份阳性,且一一对应,国内MRT抗原只检出10份阳性。结果表明全乳iELISA敏感性好,操作方便快捷,具有血清学检测所不具备的许多突出优点。     

日粮营养水平对奶牛乳蛋白合成的影响及其作用机理的研究进展

乳蛋白作为乳中重要的组成成分,含有人体所需的几乎所有必需氨基酸。然而,奶牛乳蛋白的合成受很多因素影响,如日粮组成、遗传因素、饲养环境等,但具体影响机制尚不明确。因此,研究乳蛋白合成机理,结合营养调控措施提高其在乳中的含量,成为目前研究的热点和重点。作者就目前日粮营养水平对奶牛乳蛋白合成的影响及其作用机理的研究进行了综述。     

高钙牛奶稳定性研究

钙强化后的高钙牛奶可以提供更多利于人体的钙质,研究了制备高钙牛奶时所需要的钙源、乳化剂以及增稠剂,采用正交试验确定了复配稳定剂的成分及用量,并利用粒径分析仪对高钙牛奶稳定性进行了研究.     

Risk behaviours for milk-borne diseases transmission along the milk chain in The Gambia and Senegal

The objective of this study was the characterisation of the traditional milk chain in Western Region (The Gambia) and Kolda (Southern Senegal); and the analysis of milk chain actors' risk behaviours for milk-borne diseases transmission. For this purpose, cattle herds involved in milk production, milk collectors, milk vendors and small-scale milk processing units were surveyed in the two study sites. A similar general milk chain organisation was found in the two sites with some particularities in farm management, compliance with hygienic measures at different levels, treatment of milk and milk consumption patterns. This results in a variable degree of risk of consumers' exposure to milk-borne diseases. Although the quality of the milk has been improved with the development of small-scale milk processing units, serious efforts are still needed with respect to pasteurisation procedure and to change the mindset of consumers who prefer in their majority drinking raw milk, fresh or soured, without any prior treatment.     

特色乳的功能活性研究进展

与牛乳相比,特色乳的营养物质含量丰富,具有多种生物活性,如抗菌活性、抗肿瘤活性和缓解疲劳作用等,但消费者对特色乳的营养价值了解较少,其产量、市场占比与消费量均较低.目前特色乳研究主要集中在对营养成分的分析及单一的功能活性,忽略了特色乳中所有功效成分的整体效果,对特色乳的功能活性成分、生理作用及作用机制缺少系统研究.本文...     

乳清蛋白在婴儿食品中的应用进展

母乳是婴儿最理想的食品。但是当母乳不足时,婴儿就需要补充婴儿配方食品。目前大部分的婴儿配方食品是来源于牛乳的。母乳与牛乳来源的婴儿配方食品在组成上最主要的区别是乳清蛋白的成分。主要讨论母乳与牛乳在蛋白上的区别以及在婴儿食品中添加乳清蛋白的优点。     

Effects of season and agro-ecological zone on the microbial quality of raw milk along the various levels of the value chain in Uganda

Dairy production in Uganda is pasture-based and traditional Ankole cattle make up 80% of the cattle herd, reared in both pastoral and agro-pastoral ecological zones. Regardless of the zone, milk quality is lowest in production basin during the dry season when ambient temperatures are highest and water is scarce. Poor hygiene and quality management contributed to the deterioration of raw milk quality during its storage and delivery to the final consumer, and concealed the seasonal effect when milk reached urban consumption areas. Poor milk quality is a challenge for the Ugandan Dairy Development Authorities who wish to make the milk value chain safe. This study provides baseline information for the implementation of an HACCP-based system to ensure the hygienic quality of milk from the farm to the market place.     

复原乳鉴别指标的研究进展

复原乳是炼乳和全脂乳粉与水勾兑成的原料乳,随着乳制品需求的增加,往其中掺入复原乳现象日益严重,因此复原乳的检测成为牛乳质量的重要指标之一,被广大生产厂家和消费者所重视。本文重点介绍乳制品中荧光物质、热处理产物、乳果糖含量和蛋白质理化性质等4类复原乳鉴别指标的研究进展。     

山羊乳中环鸟苷酸与泌乳

本试验对不同产乳量的健康奶山羊乳中环鸟苷酸(cGMP)和核糖核酸(RNA)的含量及葡萄糖-6-磷酸脱氢酶(G-6-PDH)的活性进行了测定,并分析了它们与产乳量之间的关系。结果表明:乳中cGMP和RNA的含量均与产乳量极显著相关(P<0.01)。高产羊与低产羊之间乳中cGMP含量存在显著差异(P<0.05)。因此认为,cGMP有促进乳生成作用。     

Factors influencing the content of urea in the milk of ewes

In total records of 363 East Friesian breed of sheep and 15 Lacaunes from 15 flocks located in Lower Austria, Upper Austria and Styria were available to investigate the influences on milk urea content. In one flock different groups of ewes were fed with low, medium and high amounts of energy and protein, but constant protein and energy ratio. The milk urea levels exhibited to statistically significant differences but the tendency of the feeding effect could be confirmed. Additional parameters influencing the urea content of milk of ewes are: herd specific factors, stage of lactation, mastitis, preservation and different analytical methods. The content of urea in milk is not suitable for assessment of the energy/protein-ratio of ewes with mastitis problems. Due to the special composition of sheep milk it is important to take account of the analytical method for determination of urea. Thus milk urea of one flock should be evaluated but not of individual sheep. In spite of these influence factors the determination of milk urea is a valuable tool for assessment of the energy and protein intake.     

羊奶及其制品稳定性的研究进展

对羊奶的热稳定性、酒精稳定性、凝乳特性及羊奶制品(羊奶粉、羊奶酸奶)稳定性的影响因素进行综述.研究表明:温度、pH值、离子浓度等对羊奶的稳定性都有显著的影响.温度在120～140℃范围内时,随着加热温度的升高,羊奶的热稳定性明显降低;30～80℃范围内,酒精稳定性随温度的升高而降低.pH6.7时,羊乳的热稳定性最好,pH6.4～7.2时,随pH值升高,羊乳的酒精稳定性增强.无机盐离子Ca2+对羊奶热稳定性和酒精稳定性的影响作用相似,稳定性均随Ca2+浓度的增大而降低.对于羊奶制品,降低水分活度可以提高其贮藏稳定性,乳清蛋白和酪蛋白含量的增加会降低酸奶贮藏期间的滴定酸度、黏度及持水性.另外,发酵酸奶所用稳定剂的不同、贮藏温度的不同也会影响制品的稳定性.