牛乳体细胞数与乳蛋白含量相关性的研究

对呼和浩特郊区一牧场30头荷斯坦乳牛进行6个月单个采样，共得427个有效样本，检测乳样中体细胞数、酪蛋白（包括α-酪蛋白、β-酪蛋白、κ-酪蛋白）、乳清蛋白、总蛋白、游离氨基氮、酪蛋白／总蛋白和乳清蛋白／总蛋白。结果表明，乳中总蛋白、游离氨基氮含量及乳清蛋白／总蛋白与SCC呈显著正相关；酪蛋白／总蛋白与SCC呈显著负相关；乳清蛋白含量与SCC呈极显著正相关。酪蛋白、α-酪蛋白／酪蛋白、β-酪蛋白／酪蛋白、κ-酪蛋白／酪蛋白与SCC的相关性不显著。酪蛋白含量与总蛋白含量呈极显著的正相关，与游离氨基氮含量、乳清蛋白／总蛋白呈极显著的负相关。乳清蛋白含量与游离氨基氮、总蛋白含量呈极显著正相关。     

牛乳体细胞数与乳中离子含量相关性的研究

对呼和浩特市郊区一牧场30头荷斯坦乳牛进行6个月跟踪采样,共得427个有效样本。根据体细胞数的高低将乳样分成五个不同的组,分别测定样本的氯、钾、钠、游离钙、总钙含量。结果表明:牛乳中氯、钠的含量与SCC呈显著的正相关(p＜0．001);游离钙含量与SCC有一定的负相关(p＜0．05);总钙、钾离子的含量与SCC的相关性不显著(p＞0．05)。乳中体细胞数和乳中氯、钾、钠、游离钙、总钙含量与月份没有相关性(p＞0．05)。氯与总钙有显著的正相关性(p＜0．001);乳中氯离子与钠离子之间;总钙与游离钙之间有一定的正相关(p＜0．05);钠离子与总钙之间有显著的正相关(p＜0．01)。其余离子之间相关性均不显著(p＞0．05)。     

鲜牛乳中体细胞数检测方法探讨

体细胞数是衡量鲜牛乳卫生状况的重要指标之一，体细胞数的提高会使牛乳中蛋白酶和解脂酶升高，使乳清蛋白含量升高，酪蛋白含量降低，从而使乳制品的货架期缩短，乳制品的风味发生改变。本文通过显微镜检测法、4％NaOH凝乳试验法两种方法的比较试验，探讨在实际生产中鲜牛乳体细胞敖的最佳检测方法及检测时限，以帮助乳制品生产企业加强对牧场的监管和在收购鲜牛乳的过程中快速、准确评判鲜牛乳的品质，确保生产出优质的乳制品供应市场。     

水牛乳体细胞数与理化性质关系的研究

测定麽拉水牛、尼里-拉菲水牛、高代三品种杂交水牛、一代杂交水牛乳中的体细胞数(Somatic Cell Count,SCC)及其理化性质,分析水牛乳SCC与理化性质之间的关系,探讨了水牛乳SCC水平对理化性质的影响。结果表明:在不同SCC水平下,水牛乳蛋白质、脂肪、总固形物、冰点、酒精阳性率变化不显著,水牛乳非脂固形物、乳糖、酸度、比重随着SCC的升高而显著降低,隐性乳房炎患病率随着SCC的升高而显著增加;在所测样品中,麽拉、尼里-拉菲水牛乳SCC>30×104mL-1,三品种杂交以及一代杂交水牛乳的SCC>50×104mL-1时,非脂固形物、乳糖、酸度、比重均值以及隐性乳房炎患病率变化更显著。     

牛乳体细胞数的检测方法

讨论了体细胞数与乳腺炎的关系以及体细胞数对牛乳成分及产奶量损失的影响。主要介绍了4种常用的体细胞数的检测方法，即加利福尼亚细胞数测定法(CMT)，威斯康辛乳腺炎试验(WMT)，电子体细胞计数法(DHI)和直接镜检法(CMSCC)。     

ATP生物发光技术快速检测牛乳体细胞数

探索利用ATP生物发光技术快速检测牛乳体细胞数的可行性.利用ATP生物发光技术测定牛乳体细胞ATP浓度,根据体细胞中ATP的浓度与体细胞数成正比的原理,推算出牛乳中的体细胞数,并与显微镜计数法对比,分析两种方法之间的相关性.结果表明:ATP生物发光技术的检测结果与显微镜计数法有很好的相关性,是一种快速、简便的检测牛乳体细胞的方法.     

牛奶体细胞数与产奶性能相关性分析

本试验运用2003年DHI报表体系,对西安市奶牛繁育中心的良种奶牛场110头左右的荷斯坦泌乳牛奶样进行分析,然后统计体细胞数和产奶性能的相关性.结果表明不同胎次,不同月份体细胞数与日产奶量和乳脂率负相关程度,和与乳蛋白率正相关的程度不同.其中,一胎牛体细胞数与日产奶量的相关系数差异极显著所占比例较大(60%);二月、八月、九月、十一月及十二月体细胞数与日产奶量相关系数差异显著和极显著比例较大(分别为75%、75%、50%、50%、50%);二月体细胞数与乳蛋白率相关系数显著比例较大(75%);八月、九月、十月及十一月体细胞数与乳脂率相关系数显著比例较大(分别为50%、75%、75%、75%).说明胎次对体细胞数与产奶性能的相关的影响相对较小,月份的影响相对较大.     

牛乳体细胞数与内源酶的关系

对某牧场30头荷斯坦奶牛的434个奶样进行体细胞数、NAG酶、过氧化物酶、过氧化氢酶、脂酶、游离脂肪酸含量的测定。结果表明,夏季牛乳中体细胞数高于秋季,九月份达到最高水平;随着牛乳体细胞数升高,NAG酶、过氧化物酶、过氧化氢酶、脂酶、游离脂肪酸含量变化极显著（P〈0.01）;除过氧化物酶与脂酶呈显著正相关（P〈0.05）外,体细胞数、其他内源酶及游离脂肪酸间均呈极显著正相关（P〈0.01）。     

牛乳中体细胞数与乳成分和部分理化性质的相关性研究

对呼和浩特郊区一牧场30头荷斯坦乳牛进行6个月单个采样,共得452个有效样本,检测乳样包括:体细胞数、脂肪、蛋白质、乳糖、总固形物、细菌总数、比重、黏度、电导率、氯糖数、滴定酸度和pH值。结果表明,蛋白质质量分数与牛乳中的体细胞数(Somatic CellCount,SCC)SCC呈显著正相关(P<0.05);乳糖含量与SCC呈显著负相关(P<0.001);脂肪、总固形物质量分数、电导率、氯糖数与SCC呈极显著正相关(P<0.001)。细菌总数、比重、黏度、滴定酸度、pH值与SCC的相关性不显著。从5～10月,乳中体细胞数有逐渐降低趋势,9月骤然升高,其中5月和9月样品平均体细胞数较高,分别为78×104 mL-1和96×104 mL-1。10月份样品平均体细胞数最低为28×104 mL-1。     

不同体细胞数的原料乳品质变化的比较研究

通过分析比较5组不同体细胞数(SCC)原料乳的主要成分和特性(蛋白质、脂肪含量、酪蛋白的含量等)、脂肪分解情况(脂肪酶活力、游离脂肪酸及其占总脂肪的比例)以及蛋白质水解程度(水溶性氮、非蛋白氮占总氮的比例以及酪蛋白构成)的变化情况,探讨不同SCC对原料乳品质的影响。结果表明：当SCC小于4.0×105个/mL时,原料乳的成分没有显著的差异(P＞0.05);随着SCC的增大,原料乳的脂肪水解程度增强,但SCC小于4.0×105个/mL的两组原料乳的脂肪水解程度没有显著差异(P＞0.05);不同SCC原料乳的酪蛋白构成表现不同,其蛋白质水解程度(WSN/TN,NPN/TN)随SCC的增大而增加,但SCC在4.0×105 个/mL以下的两组原料乳的蛋白水解程度没有显著差异(P＞0.05)。     

生乳中体细胞数对乳品质量安全的影响研究进展

体细胞数增加会改变乳成分、影响牛乳风味及缩短乳制品货架期,并且使乳中抗生素和药物残留的风险增加。乳中体细胞数是衡量乳畜健康、乳品质量与安全的标准,也是国际判定隐形乳房炎的重要指标。为了保障乳品质量和安全,许多国家规定了生乳中体细胞数的限量。本文从体细胞数和乳品质量与安全的关系、不同国家对生乳中体细胞数的限量及影响体细胞数的因素和体细胞数的检测方法等方面作一综述。     

精料和饱和脂肪酸对奶牛生产性能和乳中脂肪酸组成的影响

为研究高精料和饱和脂肪酸对泌乳早期奶牛生产性能和乳中脂肪酸组成的影响。选择产后55 d左右的泌乳高峰期奶牛30头,根据随机区组设计原则,按照产奶量、胎次和泌乳天数将奶牛分为对照组(C)、高精料组(HC)和饱和脂肪酸组(FA),分别饲喂以干物质为基础含精料40%,60%和40%添加3%饱和脂肪酸的等蛋白日粮。结果 HC组产奶量(26.53±3.72)kg/d和FA组产奶量(26.98±3.36)kg/d显著高于C组(24.43±2.63)kg/d。FA组乳脂含量显著高于HC组(P≤0.05),HC组有低于C组的趋势(P=0.15)。FA组短链脂肪酸的含量显著低于C组(P≤0.05),HC组与C组差异不显著;HC组长链脂肪酸的含量显著低于FA组(P≤0.05),与C组差异不显著。HC组饱和脂肪酸含量显著高于FA组(P≤0.05)、FA组单不饱和脂肪酸含量显著高于C组和HC组(P≤0.05)、HC组多不饱和脂肪酸高于C组(P≤0.05)、各组间共轭亚油酸(10c12t CLA)含量差异不显著。结论为饲喂高精料日粮能够提高产奶量、降低乳脂率、增加乳脂中中链饱和脂肪酸和多不饱和脂肪酸含量。日粮添加饱和脂肪酸能够提高产奶量、增加乳脂率、增加单不饱和脂肪酸含量。     

Transmission Electron Microscopy Study of Casein Micelle in Raw Milk with Different Somatic Cell Count Levels

The relationship between elevated raw milk somatic cell count (SCC) and casein micelle dimension was investigated by transmission electron microscopy (TEM). Milk samples collected from the dairy cattle with three different levels of SCC (<200,000, 200,000 to 800,000, and >800,000 cells/ml) were studied by TEM. The results indicated that an increase in SCC resulted in a decrease in the casein micelle size with an increase in their aggregation. The present research supported the hypothesis that elevated proteolytic activity, reduced secretary ability of the mammary glands, lower electrostatic and steric repulsion as well as different mineral contents of mastitic milk could affect casein micelle properties.     

气相色谱法快速测定牛奶中脂肪酸

牛奶中高级脂肪酸经甲酯化后，利用气相色谱法测定，结果表明十二碳以上的长链脂肪酸的线性范围好，相关系数为r=0．9991以上，回收率在89．0％～109％之间。方法简便，快速。     

体细胞数对半硬质山羊奶干酪品质影响的研究

山羊奶特殊的顶浆分泌机制使正常山羊奶的体细胞数要高于正常牛奶和绵羊奶.因此,有必要探讨高体细胞数对山羊奶成分及其半硬质干酪品质的影响.本研究针对三组不同体细胞数(＜5×105/ml、5×105～1×106/ml和1×106～1.5×106/ml)非乳房炎山羊奶的分析结果表明该范围内的体细胞数对山羊奶的成分,半硬质干酪的产量和成分均无显著的影响.但是,在60d和120d成熟之后,高体细胞数的干酪具有最高的水溶性氮占总氮的比率和12%三氯乙酸可溶性氮占总氮的比率;同时,高体细胞数导致成熟干酪的硬度和咀嚼性降低,弹性、内聚性和粘性都显著增高.本研究结果将为山羊奶体细胞形成机制的研究和山羊奶分级体系的建立提供有用的数据信息.     

Somatic cell count during and between milkings

The objectives of the study were to determine 1) how sampling time between milkings affects the sensitivity and specificity of somatic cell count (SCC) as an indicator for intramammary infection (IMI) status, and 2) which cells are responsible for the diurnal variation in SCC. Six Prince Edward Island, Canada, dairy herds were selected. Quarter samples for SCC were collected immediately before the a.m. milking (pre-a.m.), halfway through the a.m. milking, immediately after the a.m. milking, every 60 min after detachment of the milking unit, and immediately before the p.m. milking (pre-p.m.). Compared with the geometric mean SCC at the pre-a.m. milking, SCC of quarters with no IMI between milkings was higher up to 7 h after milking. The pre-p.m. SCC was significantly lower than the pre-a.m. SCC in quarters with no IMI. Specificity of SCC at a cutoff of 200,000 or 500,000 cells/mL as an indicator for IMI status declined substantially after the a.m. milking. In quarters with elevated SCC, the proportion of polymorphonuclear leukocytes was larger immediately after milking. For accurate interpretations of SCC tests—whether by a laboratory, portable SCC device, or the California Mastitis Test—veterinarians, researchers, and udder health advisors should take milk samples immediately before milking.     

Effect of Dietary Starch or Micro Algae Supplementation on Rumen Fermentation and Milk Fatty Acid Composition of Dairy Cows

Two experiments with rumen-fistulated dairy cows were conducted to evaluate the effects of feeding docosahexaenoic acid (DHA; C22:6 n-3)-enriched diets or diets provoking a decreased rumen pH on milk fatty acid composition. In the first experiment, dietary treatments were tested during 21-d experimental periods in a 4 × 4 Latin square design. Diets included a control diet, a starch-rich diet, a bicarbonate-buffered starch-rich diet, and a diet supplemented with DHA-enriched micro algae [Schizochytrium sp., 43.0 g/kg of dry matter intake (DMI)]. Algae were supplemented directly through the rumen fistula. The total mixed ration consisted of grass silage, corn silage, soybean meal, and a standard or glucogenic concentrate. The glucogenic and buffered glucogenic diet had no effect on rumen fermentation and milk fatty acid composition because, unexpectedly, no reduced rumen pH was detected. The algae diet had no effect on rumen pH but provoked decreased butyrate and increased isovalerate molar proportions in the rumen. In addition, algae supplementation affected rumen biohydrogenation of linoleic and linolenic acid as reflected in the modified milk fatty acid composition toward increased conjugated linoleic acid (CLA) cis-9 trans-11, CLA trans-9 cis-11, C18:1 trans-10, C18:1 trans-11, and C22:6 n-3 concentrations. Concomitantly, on average, a 45% decrease in DMI and milk yield was observed. Based on these drastic and impractical results, a second animal experiment was performed for 20 d in which 9.35 g/kg of total DMI of algae were incorporated in the concentrate and supplemented to 3 rumen-fistulated cows. Algae concentrate feeding increased rumen pH, which was associated with decreased rumen short-chain fatty acid concentrations. Moreover, a different shift in rumen short-chain fatty acid proportions was observed compared with the first experiment because molar proportions of butyrate, isobutyrate, and isovalerate increased, whereas acetate molar proportion decreased. The milk fatty acid profile changed as in experiment 1. However, the decrease in DMI and milk yield was less pronounced (on average 10%) at this algae supplementation level, whereas milk fat percentage decreased from 47.9 to 22.0 g/kg of milk after algae treatment. In conclusion, an algae supplementation level of about 10 g/kg of DMI proved effective to reduce the milk fat content and to modify the milk fatty acid composition toward increased CLA cis-9 trans-11, C18:1 trans, and DHA concentrations.