牛肉、牛奶中可的松和氢化可的松含量分析

采用液相色谱-串联质谱技术分析我国部分地区市售牛肉、牛奶中可的松和氢化可的松的含量水平。均质的牛肉或牛奶样品在乙酸-乙酸钠缓冲液中酶解后用甲醇提取,提取液用石墨化碳黑固相萃取小柱和氨基固相萃取小柱净化,洗脱液氮吹至干并用甲醇溶液定容,液相色谱-串联质谱测定。采用SPSS?21.0软件进行数据分析。对采自我国9?省市的346?份牛肉和牛奶样品进行检测,分析牛肉和牛奶中可的松和氢化可的松的存在水平。牛肉和牛奶中均检出可的松和氢化可的松,检出率在86.1%～100.0%之间,检出含量范围为0.02～74.88?μg/kg。牛肉中可的松和氢化可的松的含量平均值（中位数）分别为1.69（1.14）?μg/kg和12.16（8.14）?μg/kg,牛奶中可的松和氢化可的松的含量平均值（中位数）分别为0.23（0.23）?μg/kg和0.72（0.72）?μg/kg。牛肉和牛奶中氢化可的松与可的松的含量均呈显著正相关。     

QuEChERS/高效液相色谱-串联质谱测定婴幼儿配方奶粉中氢化可的松和氟氢可的松醋酸酯

建立了婴幼儿配方奶粉中氢化可的松和氟氢可的松醋酸酯激素残留的高效液相色谱-串联质谱（HPLC-MS/MS）测定方法。样品经水分散后以乙腈提取,氯化钠盐析,以N-丙基乙二胺（primary secondary amine,PSA）和中性氧化铝（Al2O3-N）净化,Waters XBridge C18色谱柱分离,电喷雾正离子扫描,多反应监测（MRM）模式检测,基质匹配标准溶液外标法定量。在优化条件下,目标化合物在3个加标水平（1.25、5.00、12.50 μg/kg）下的平均回收率为80.6%~102.1%,相对标准偏差（RSD）为1.64%~4.22%,方法检出限（LOD）为0.40 μg/kg,方法定量限（LOQ）为1.25 μg/kg。应用本方法对28批次婴幼儿配方奶粉进行测定,发现2批次样品检出氢化可的松。方法简便快速、灵敏度高、重现性好,能满足婴幼儿配方奶粉中氢化可的松和氟氢可的松醋酸酯激素残留的快速检测要求。     

液相色谱-串联质谱法测定饲料中氢化可的松

目的 建立液相色谱-串联质谱法(liquid chromatography-tandem mass spectrometry,LC-MS/MS)测定饲料中氢化可的松含量的分析方法.方法 饲料样品中的氢化可的松经甲醇提取、石墨化碳黑固相萃取柱结合氨基固相萃取柱净化,配制基质匹配标准溶液,外标法定量.色谱采用乙腈(A)和0...     

气相色谱法测定丁酸氢化可的松乳膏中三氯叔丁醇含量

目的用气相色谱法测定丁酸氢化可的松乳膏中三氯叔丁醇含量。方法采用聚乙二醇为固定液的毛细管柱(DB-WAX,30m×0.32mm,0.5μm),程序升温,初始温度90℃,以50°℃/min的速率升温至200℃,保持0.5 min;检测器为氢火焰离子化检测器(FID),温度250℃,进样口温度220℃,载气为氮气,流速5.0 mL/min,进样量1μL。结果三氯叔丁醇进样量在0.010～0.101μg(r=0.999 9)范围内有良好的线性关系,平均加样回收率(n=9)100.40%。结论此法灵敏度高,操作简便,准确可靠,可用于测定丁酸氢化可的松乳膏中三氯叔丁醇的含量。     

牛初乳中乳铁蛋白的分离和纯化

利用超滤、盐析和层析三种方法,采用单因素实验和正交实验对酸牛乳清中的乳铁蛋白进行分离和纯化,得到盐析的最佳条件为:先以50%硫酸铵除去杂蛋白,然后在30°C,pH8.5,80%硫酸铵进行盐析。用CM-SephadexC-100进行层析,进样量为2mL,洗脱液pH为7.4时可以得到乳铁蛋白纯品。SDS-PAGE凝胶电泳结果表明,牛初乳中乳铁蛋白的纯度为92%,分子量大约为78000±2000Da。      

牛初乳中乳铁蛋白的分离和纯化

利用超滤、盐析和层析三种方法,采用单因素实验和正交实验对酸牛乳清中的乳铁蛋白进行分离和纯化,得到盐析的最佳条件为:先以50%硫酸铵除去杂蛋白,然后在30°C,pH8.5,80%硫酸铵进行盐析。用CM-SephadexC-100进行层析,进样量为2mL,洗脱液pH为7.4时可以得到乳铁蛋白纯品。SDS-PAGE凝胶电泳结果表明,牛初乳中乳铁蛋白的纯度为92%,分子量大约为78000±2000Da。     

膜分离牛初乳中乳铁蛋白的工艺参数研究

研究采用膜分离技术分离牛初乳中乳铁蛋白的工艺条件,并摸索出膜污染的解决办法。以牛初乳为原料,采用单因素试验和二次通用旋转组合设计法优化膜分离乳铁蛋白的工艺条件,并进行响应面分析,比较水法、碱法和水法结合碱法清洗膜的方法。结果显示:提取乳铁蛋白的最适温度38℃、操作压力0.19 MPa、pH 6.9。在此条件下得到膜通量53.2 L/m2.h,膜效能0.79 g/m2.min。膜清洗采用水洗10 min,0.5 mol/L NaOH与4%NaClO混合液清洗15 min,膜通量恢复率可以达到95%以上。     

牛初乳冻干粉和常乳冻干粉的降血糖及抗氧化作用

目的:研究牛初乳冻干粉（LBC）和常乳冻干粉（LM）降血糖及抗氧化作用。方法:采用生化分析方法测定自由基清除活性及IGFs和胰岛素含量。建立小鼠四氧嘧啶糖尿病模型,分别给予降糖灵（100 mg/kg）、LM（600 mg/kg）和LBC（100 mg/kg、600 mg/kg）,以正常小鼠作对照。30 d后,测定血糖、糖耐量及抗氧化等指标。结果:LBC清除O₂^-·,DPPH·的EC₅₀值为245.3,167.2μg/m L,IGF-1、IGF-Ⅱ和胰岛素含量分别为1146.5、1303.0、128.4 ng/g。LM对羟自由基有一定清除作用,IGFs含量显著低于LBC,未检出胰岛素。LBC对糖尿病小鼠病症有明显改善;能显著降低血糖水平,降低血清MDA和TC含量;能提高糖耐量和血液SOD活性。LM对血糖水平和抗氧化指标无明显改善。结论:LBC比LM具有更高的降糖活性和自由基清除活性,对糖尿病小鼠有降血糖及抗氧化作用。      

牛初乳及过渡乳中类胰岛素生长因子-I含量测定及其变化

牛初乳及过渡乳中类胰岛素生长因子-I(IGF—I)含量随产后泌乳的进行急剧下降，泌乳前5d，初乳中的IGF—I以游离形态为主，游离IGF—I比例由71．1％下降到50.64％；之后过渡中的IGF-I主要以结合形态为主，结合态IGF—I的比例由51.41％上升到60.1％。从初乳到过渡乳中IGF—I存在形态的变化具有重要的生物学意义。     

牛初乳的功能性研究和在食品中的最新应用

牛初乳？因为其富含免疫球蛋白而在当今备受青睐和关注,但是,牛初乳对于人类健康上所能起到的功能及其在食品上的应用至今仍备受辩驳和争议,同时对其功能也经历了或大肆吹捧或一棒打死的情况？使得牛初乳产品的销售在市场上也屡次经历了大起大落。[编按]     

Genetic parameters of colostrum traits in Holstein dairy cows

The main objective of this study was to assess the genetic background of colostrum yield and quality traits after calving in Holstein dairy cows. The secondary objective was to investigate genetic and phenotypic correlations among laboratory-based and on-farm–measured colostrum traits. The study was conducted in 10 commercial dairy herds located in northern Greece. A total of 1,074 healthy Holstein cows with detailed pedigree information were examined from February 2015 to September 2016. All cows were clinically examined on the day of calving and scored for body condition. All 4 quarters were machine-milked, and a representative and composite colostrum sample was collected and examined. Colostrum total solids (TS) content was determined on-farm using a digital Brix refractometer. Colostrum fat, protein, and lactose contents were determined using an infrared milk analyzer, and energy content was calculated using National Research Council (2001) equations. Dry period length (for cows of parity ≥2), milk yield of previous 305-d lactation (for cows of parity ≥2), age at calving, parity number, season of calving, time interval between calving and first colostrum milking, and milk yield were recorded. Each trait (colostrum yield and quality traits) was analyzed with a univariate mixed model, including fixed effects of previously mentioned factors and the random animal additive genetic effect. All available pedigrees were included in the analysis, bringing the total animal number to 5,662. Estimates of (co)variance components were used to calculate heritability for each trait. Correlations among colostrum traits were estimated with bivariate analysis using the same model. Mean percentage (±SD) colostrum TS, fat, protein, and lactose contents were 25.8 ± 4.7, 6.4 ± 3.3, 17.8 ± 4.0, and 2.2 ± 0.7%, respectively; mean energy content was 1.35 ± 0.3 Mcal/kg and mean colostrum yield was 6.18 ± 3.77 kg. Heritability estimates for the above colostrum traits were 0.27, 0.21, 0.19, 0.15, 0.22, and 0.04, respectively. Several significant genetic and phenotypic correlations were derived. The genetic correlation of TS content measured on-farm with colostrum protein was practically unity, whereas the correlation with energy content was moderate (0.61). Fat content had no genetic correlation with TS content; their phenotypic correlation was positive and low. Colostrum yield was not correlated genetically with any of the other traits. In conclusion, colostrum quality traits are heritable and can be amended with genetic selection.     

Relationship between intramammary infection and antibody concentrations in Jersey and Holstein colostrum

Feeding calves a high-quality and antibody-rich colostrum is an important management practice for supporting calf health and productivity. Colostrum quality and antibody concentrations are highly variable between cows and among quarters within a cow. Intramammary infections often occur during the time of colostrum formation; however, it is unknown if these infections ultimately affect colostrum quality and antibody concentrations. The objective of this study was to determine if antibody concentrations and Brix percentage in colostrum from infected mammary glands (quarters) differed from uninfected. In 2 cross-sectional studies, colostrum samples were aseptically collected at first milking from 110 Holstein and 89 Jersey cows at 3 Holstein and 4 Jersey commercial dairy farms in Ohio. A total of 771 quarter samples were collected, underwent bacteriological culture, and were measured for Brix percentage with a digital refractometer. When 1 infected and 1 uninfected quarter existed among the fore or rear quarters within a cow, IgG₁, IgG₂, IgA, and IgM antibody concentrations were determined via ELISA for the paired quarters (n = 82). Overall, for Holstein cows, Brix percentages were greater in multiparous than primiparous cows (30.5 vs. 23.7 ± 2.1 SEM), but an opposite pattern was observed for Jersey cows (24.3 vs. 27.2 ± 1.2 SEM). Uninfected quarters in both Holstein and Jersey multiparous cows had greater Brix percentage than colostrum from infected quarters; this pattern was absent for Holstein and Jersey primiparous cows. For Holstein cows, concentrations of IgG₁, IgG₂, and IgA were greater in multiparous cows than primiparous cows; quarter-infection status did not significantly influence antibody concentrations. For Jersey samples, antibody concentrations did not differ between primiparous and multiparous cows and were not significantly affected by quarter-infection status. The results of these works indicate that infection status at parturition does not markedly affect colostrum antibody concentrations and quality, and that other factors at the local level of the mammary gland more greatly influence colostrogenesis and antibody transport into the mammary gland during colostrogenesis.     

荷斯坦奶牛初乳中酶及激素的含量变化研究

在荷斯坦奶牛分娩后1～8 d采集当天乳样,分析了乳中部分酶的活力和激素的含量变化。结果表明,碱性磷酸酶的活力在1 d中最高,达到5.39 U(P<0.05),而后随着时间延长酶的活力下降;-γ谷氨酰转肽酶在1 d达到1002.08 U(P<0.05),而后活力开始下降,7 d达到602.76 U;黄嘌呤氧化酶和乳酸脱氢酶的活力分别在40～120 U和20～40 U之间变化,各天之间无显著性差异(P>0.05);瘦素的质量浓度在2.30～5.14 ng/mL之间变化,各天之间无显著差异(P>0.05);胰岛素的含量1 d为最高2043.40 u IU/mL(P<0.05),随时间呈逐渐下降趋势;皮质醇的质量浓度1 d最高为95.77 ng/mL(P<0.05),总体呈下降趋势;泌乳素的质量浓度1 d为9.06 ng/mL,而后逐渐下降,各天之间无显著差异(P>0.05)。     

Effects of enriching IgG concentration in low- and medium-quality colostrum with colostrum replacer on IgG absorption in newborn Holstein calves

Ingestion and absorption of greater quantities of IgG are required to increase serum IgG levels in newborn calves. This could be achieved by adding colostrum replacer (CR) to maternal colostrum (MC). The objective of this study was to investigate whether low and high-quality MC can be enriched with bovine dried CR to achieve adequate serum IgG levels. Male Holstein calves (n = 80; 16/treatment) with birth body weights (BW) of 40 to 52 kg were randomly enrolled to be fed 3.8 L of the following combinations: 30 g/L IgG MC (C1), 60 g/L IgG MC (C2), 90 g/L IgG MC (C3), C1 enriched with 551 g of CR (60 g/L; 30-60CR), or C2 enriched with 620 g of CR (90 g/L: 60-90CR). A subset of 40 calves (8/treatment) had a jugular catheter placed and were fed colostrum containing acetaminophen at a dose of 150 mg/kg of metabolic body weight, to estimate abomasal emptying rate per hour (kABh). Baseline blood samples were taken (0 h), followed by sequential samples at 1, 2, 3, 4, 5, 6, 8, 10, 12, 24, 36, and 48 h relative to initial colostrum feeding. Results for all measurements are presented in the following order, unless otherwise stated: C1, C2, C3, 30-60CR, and 60-90CR. Serum IgG levels at 24 h were different among calves fed C1, C2, C3, 30-60CR, and 60-90CR: 11.8, 24.3, 35.7, 19.9, and 26.9 mg/mL ± 1.02 (mean ± SEM), respectively. Serum IgG at 24 h increased when enriching C1 to 30-60CR, but not from C2 to 60-90CR. Similarly, apparent efficiency of absorption (AEA) values for calves fed C1, C2, C3, 30-60CR, and 60-90CR were different: 42.4, 45.1, 43.2, 36.3, and 33.4% ± 1.93, respectively. Enriching C2 to 60-90CR reduced AEA, and enriching C1 to 30-60CR tended to decrease AEA. The kABh values for C1, C2, C3, 30-60CR, and 60-90CR were also different: 0.16, 0.13, 0.11, 0.09, and 0.09 ± 0.005, respectively. Enriching C1 to 30-60CR or C2 to 60-90CR reduced kABh. However, 30-60CR and 60-90CR have similar kABh compared with a reference colostrum meal (90 g/L IgG, C3). Even though kABh was reduced for 30-60CR, results indicate that C1 has the potential to be enriched and achieve acceptable serum IgG levels at 24 h without affecting AEA.     

Comparison of total and free cortisol in bovine serum and milk or colostrum

Total (free plus protein-bound) and free cortisol concentrations in paired samples of serum and skim milk or colostrum were determined by specific radioimmunoassay after extraction or ultrafiltration. For 11 cows in established lactation mean total cortisol concentrations +/- SE in serum and milk were 4.5 +/- .7 ng/ml and .35 +/- .06 ng/ml, respectively. Concentrations of free cortisol in serum and milk were about .3 ng/ml, which is at the lower limit of the present assay. Following 200 IU Synacthen injection to 5 cows, total cortisol in serum and milk rose to 67 +/- 6.0 ng/ml and 11.4 +/- 1.5 ng/ml by 8 h postinjection, while free concentrations increased to 4.3 +/- .7 ng/ml and 6.5 +/- .8 ng/ml in serum and milk, respectively. Eight additional cows were sampled at 1 to 2 d after parturition, and total cortisol in serum and colostrum was 16.6 +/- 1.6 ng/ml and 4.4 +/- 1.3 ng/ml, and free cortisol was 2.4 +/- .4 ng/ml and 1.8 +/- .5 ng/ml, respectively. Free cortisol concentrations in colostrum or in milk from cows in established lactation, before or after adrenal stimulation, are directly related to free cortisol concentrations in the blood, while the bound cortisol in milk is more related to these two stages of lactation rather than the bound hormone in the blood. Measurement of free cortisol in milk should allow the monitoring of changes in plasma free cortisol in studies of stress in dairy cows.     

Relationship of Temperature and Humidity to Conception Rate of Holstein Cows in Hawaii

Weather data and breeding records for a Holstein herd of 1300 cows in Hawaii were evaluated to determine effects of climate on reproductive performance. The dairy is in a coastal climate near latitude 21°N. Average maximum temperature, relative humidity, and resulting temperature-humidity index for the warmest month of the year were 31 C, 44%, and 79. Average minimum temperature and attending values for the same period were 20 C, 96%, and 68. From late April to November, conception rates were correlated negatively with the average temperature-humidity index of each day of the estrous cycle beginning 11 days prior to breeding. Slopes of regression lines differed, suggesting varying sensitivity of conception rate to heat stress on different days of the cycle. The temperature-humidity index of the 2nd day prior to breeding was most closely correlated with conception rate. Conception rates declined from 66% to 35% as the index increased from 68 to 78. Only the temperature-humidity index of the 2nd day prior to breeding had a significant partial correlation coefficient when the index of the 2nd and 1st day prior to breeding, the day of breeding, and the day following breeding were each evaluated with the index of the others held constant.     

Management and production factors influencing immunoglobulin G1 concentration in colostrum from Holstein cows

Immunoglobulin G1 concentration was measured in 919 first milking colostrums from Holstein cows during a 4-yr period on a commercial dairy farm. Sources of variation analyzed for effect on colostral IgG1 concentration were season of calving, lactation number, dry period length, intercalving interval, complete lactation milk and fat production, weight of first milking colostrum, and time from calving to first milking. Weight of first milking colostrum was the variable most highly correlated (negatively) with colostral IgG1 concentration (r = -.29). Weight of first milking colostrum and lactation number of the cow were the most significant discriminators between colostrum of low and high IgG1 concentration. The implications of these results for colostrum feeding management are discussed.     

Dopamine antagonist alters serum cortisol and prolactin secretion in lactating Holstein cows

The role of dopamine in regulating glucocorticoid and prolactin secretion was investigated in lactating Holstein cows by characterizing serum cortisol and prolactin responses to fluphenazine, a dopamine receptor antagonist. Twelve anovulatory cows received an intravenous bolus injection of either saline (n = 6) or 0.3 mg of fluphenazine/kg of body weight (n = 6) in wk 2 postpartum. Blood samples were collected every 30 min for 4 h before and 4 h after saline or fluphenazine injection. Serum progesterone concentration was 0.13 ± 0.1 ng/mL and did not differ between groups. No difference in serum cortisol concentrations was detected between groups before treatments. Fluphenazine increased serum cortisol concentrations within 30 min after fluphenazine administration (>30 ng/mL) and concentrations remained elevated throughout the sampling period. Cortisol remained unchanged in saline-treated cows (<10 ng/mL). Prolactin concentrations also increased after fluphenazine administration (103.1 ± 3.1 ng/mL), but were unaffected by saline (18 ± 3.1 ng/mL). Prolactin concentrations remained elevated throughout the sampling period in fluphenazine-treated cows. Our results indicated that a dopamine antagonist increased cortisol, suggesting that endogenous dopamine, at least in part, regulates cortisol and prolactin secretion. These effects are regulated through dopamine receptors in anovulatory lactating dairy cows during the early postpartum period.     

Epidemiology of bovine colostrum production in New York Holstein herds: Prepartum nutrition and metabolic indicators

Colostrum yield and quality are influenced by prepartum nutrition and the metabolic status of the cow; however, data considering these associations on multiple dairy farms are limited. Our objective was to identify cow-level prepartum metabolic indicators, as well as farm-level nutritional strategies associated with colostrum yield and the indicator of colostrum quality, Brix %. A convenience sample of 19 New York Holstein dairies (median: 1,325 cows; range: 620 to 4,600 cows) were enrolled in this observational study. Records for individual colostrum yield and Brix % were collected by farm personnel between October 2019 and February 2021. Farms were visited 4 times, approximately 3 mo apart, to obtain feed samples of the prepartum diets, collect blood samples from 24 pre- and postpartum cows, respectively, and determine prepartum body condition score. Feed samples were submitted for analysis of chemical composition, and particle size was determined on-farm using a particle separator. Prepartum serum samples (n = 762) were analyzed for glucose and nonesterified fatty acid concentrations. Whole blood from postpartum cows was analyzed for herd prevalence of hyperketonemia (proportion of samples with β-hydroxybutyrate ≥1.2 mmol/L). A cohort of primiparous (PP; n = 1,337) and multiparous (MPS; n = 3,059) cows calving ± 14 d of each farm visit were included in the statistical analysis. Animals calving in this period were assigned results for the close-up diet composition and herd prevalence of hyperketonemia collected from the respective farm visit. Greatest colostrum yield from PP and MPS cows was associated with moderate starch [18.6–22.5% of dry matter (DM)] and a moderate herd prevalence of hyperketonemia (10.1–15.0%). Greatest colostrum yield from MPS cows was associated with moderate crude protein (13.6–15.5% of DM) and a less severe negative dietary cation-anion difference (DCAD; >−8 mEq/100 g), whereas greatest colostrum yield from PP cows was associated with low crude protein (≤13.5% of DM). In addition, a moderate proportion of the diet with particle length ≥19 mm (15.3–19.1%) was associated with lowest colostrum yield from PP and MPS cows. Highest colostrum Brix % was associated with prepartum dietary factors of low neutral detergent fiber (≤39.0% of DM) and high proportion of the diet with particle length ≥19 mm (>19.1%). In addition, low starch (≤18.5% of DM) and low and moderate DCAD level (≥−15.9 mEq/100 g) were associated with greatest Brix % from PP cows, whereas moderate DCAD (−15.9 to −8.0 mEq/100 g) was associated with greatest Brix % from MPS cows. Prepartum serum nonesterified fatty acid concentration ≥290 µEq/L was associated with increased colostrum yield, but prepartum serum glucose concentration and body condition score were not associated with colostrum yield or Brix %. These data provide nutritional and metabolic variables to consider when troubleshooting colostrum production on farms.     

Predicting Milk Yield of Holstein Cows from 306 to 395 Days in Milk

Prediction equations were determined to estimate daily milk yield from 306 to 395 d in milk for forecasting herd milk sales from Holstein cows in lactation >305 d. Data were test day milk weights for 65,322 primiparous and 119,220 pluriparous lactations of > 305 d from the Southern US. A forecast model was developed using same lactation 305 d milk yield (in classes of 500 kg increments) that gave similar predicted daily yields as models utilizing last sample milk weight information. This model has the advantage of early forecasting of later milk using projected 305-d yields.Reduced forecast models ignoring days pregnant, yield class, or both accounted for 95, 68, and 59%, and 91, 67, and 56% as much variation in daily milk as the full model for the primiparous and pluriparous cows. Percentage of 305-d milk yielded in mo 11, 12, and 13, depending on 305-d yield class, ranged from 7.1 to 7.0%, 6.2 to 6.0%, and 5.4 to 5.0%, and 5.4 to 5.0%, 4.3 to 3.9%, and 3.3 to 3.0% for first parity and pluriparous cows calving in winter and 125 d open. Cows not calving in winter or with more than 125 d open yielded more milk in extended lactation. These percentages are larger than generally assumed in studies of days open, thus indicating that cost of days open may have been overestimated.