高效液相色谱法测定蜂王浆中羟甲基糠醛含量

建立了测定蜂王浆中羟甲基糠醛含量的固相萃取-反相高效液相色谱法.蜂王浆样品用水溶解提取,提取液用亚铁氰化钾溶液和乙酸锌溶液沉降蛋白后,再用C18固相萃取小柱净化.羟甲基糠醛用甲醇从C18小柱上洗脱,氮吹浓缩至近干,残渣用流动相溶解,过0.45μm滤膜后,用高效液相色谱仪在285nm测定.本方法线性范围为0.1～20mg/L,线性相关系数R2=0.9993;在0.2～10mg/kg添加水平时,回收率在87.2%～93.1%之间,相对标准偏差为0.9%～3.4%,方法检出限为0.2mg/kg.     

高效液相色谱法测定奶粉中酪蛋白磷酸肽的含量

采用高效液相色谱(HPLC)法对奶粉中酪蛋白磷酸肽(CPP)含量进行测定,样品通过调节p H、超声提取、离心分离和浓缩等方式进行前处理,C18柱分离,流动相为乙腈+0.1%TFA和水+0.1%TFA,梯度洗脱,检测波长215 nm,以保留时间定性,外标法定量,并与钡-乙醇沉淀法测定的结果进行对比。结果表明,HPLC检测CPP与杂质分离效果良好,线性范围0.1~2.0 mg/m L,加标0.1%~0.3%,回收率97.59%~100.00%;并测定多个厂家奶粉中的微量CPP,与实际添加量较接近,适用性良好,表明该方法简便,准确度和灵敏度高,其检测限为15.34 mg/kg、定量限为51.14mg/kg,适用于奶粉中微量CPP含量检测。钡-乙醇沉淀法测定奶粉中CPP含量结果与实际差别太大,不适用于奶粉中CPP含量的测定。     

运动功能饮料中合成着色剂测定及全自动固相萃取仪的应用

建立了应用全自动固相萃取仪进行样品净化,高效液相色谱DAD检测器测定运动功能饮料中6种合成着色剂的方法。样品用去离子水稀释,经过固相萃取小柱净化后,经高效液相色谱仪DAD检测器测定。结果表明:6种合成着色剂3个水平(0.001、0.005、0.050g/kg)加标回收率为94.5%~100.9%,相对标准偏差为0.32%~1.02%(n=6),检出限分别为柠檬黄0.05mg/kg、日落黄0.1mg/kg、胭脂红0.1mg/kg、诱惑红0.1mg/kg、苋菜红0.1mg/kg、亮蓝0.1mg/kg。此方法具有简单、快速、准确等优点,适用于运动饮料中柠檬黄、日落黄、胭脂红、诱惑红、苋菜红和亮蓝的同时测定。     

冷蒸气原子吸收光谱法测定接装纸中的Hg

为建立微波消解-冷蒸气原子吸收光谱法测定接装纸中Hg含量的方法,考察了微波消解、盐酸(反应介质)浓度、硼氢化钠(还原荆)浓度和载气流速等测定条件对测定结果的影响,并采用该方法测定16个国产接装纸样品中的Hg含量.结果表明:①采用HNO3-HCI-H2O2-HF体系微波消解样品,样品消解完全;②Hg测定的最佳反应条件为硼氢化钠浓度0.3%(质量分数),载液中盐酸浓度5%(体积分数),载气流速为95 mL/min;③Hg的检出限为0.016 μg/L,重复性RSD≤3.0%,回收率为90.0%～98.0%;④16个接装纸样品中的Hg含量均低于0.6 mg/kg,其中有2个样品未检出,含量为0～0.1 mg/kg的样品有6个,含量为0.1～0.5 mg/kg的样品有7个,含量为0.599 mg/kg的样品只有1个.     

涡旋振荡提取-高效液相色谱-紫外检测法测定铁叶酸片中的叶酸含量

摘要：目的建立涡旋振荡提取-高效液相色谱-紫外检测法（high performance liquid chromatography-ultraviolet, HPLC-UV）快速测定保健食品铁叶酸片中叶酸含量的分析方法。方法样品研磨成粉后,取样0.1 g, 加入0.3%的氨溶液25 mL,之后立即在旋涡混合器中涡旋振荡提取3 min。静置3 min后取上清液,滤膜过滤后,结合HPLC-UV方法进行含量检测。结果改进后的涡旋振荡提取法相比于常规的超声及加热提取法,前处理时间更短,提取效率更高,而且能够良好的避免基质中亚铁离子对含量测定的影响。叶酸在0.0054~0.2143 mg/mL浓度范围内线性良好（r2=0.9999）,实际样品平均回收率为98.18%~99.88%,相对标准偏差为0.89%~1.12%（n=6）。结论此改进后的方法准确、高效、简便、重现性良好,适用于保健食品铁叶酸片中叶酸含量的测定。     

SPE-HPLC测定黄瓜、番茄中敌菌灵和异菌脲残留量

建立采用固相萃取-高效液相色谱法同时测定黄瓜、番茄中敌菌灵和异菌脲农药残留量的分析方法。样品用乙腈均质法提取盐析后脱水,经SPE固相萃取净化,浓缩仪浓缩后进液相色谱分离与检测,外标法定量。对样品进行添加回收率试验,添加浓度分别为0.1、0.5、1.0 mg/kg,敌菌灵和异菌脲2种农药的回收率在82.5%~102.8%之间,标准偏差(RSD)在2.95%~8.68%之间,最低检出限为0.02 mg/kg。该方法满足黄瓜、番茄中敌菌灵和异菌脲农药残留量的检测要求。     

高效液相色谱法测定黄瓜果实中6-苄基腺嘌呤残留量

建立了测量黄瓜果实中6-苄基腺嘌呤残留量的高效液相色谱法。样品经甲醇提取,C_(18)固相萃取柱净化,浓缩定容后上样分析。该方法在0.04～10.0 μg/mL范围内线性良好,R~2为0.999 8,检出限为0.1 mg/kg,定量限为0.2 mg/kg,精密度为0.90%,回收率在86.77%～96.45%范围内,重复性为3.69%。该方法适用于黄瓜果实中6-苄基腺嘌呤残留量的测定。     

电感耦合等离子发射光谱法测定乳制品中的铝含量

目的建立电感耦合等离子发射光谱法测定乳制品中铝的分析方法,并进一步优化样品前处理方法。方法采用微波消解法处理牛奶和乳扇样品,电感耦合等离子发射光谱测定样品中的铝含量,并进行了连续测定7次的精密度实验和加标回收准确度实验。结果铝元素在0～10 mg/L范围内线性关系良好,方法的检出限是0.6 mg/kg,定量限是1.8 mg/kg,其精密度为5.09%～6.05%,加标回收率94%～101.92%。通过测定市售乳制品发现,牛奶中铝含量正常,乳扇中铝含量偏高。结论本方法简便准确,为研究乳制品中金属元素含量提供一定参考。     

高效液相色谱法测定固体饲料中的二氢吡啶

目的建立一种高效液相色谱测定固体饲料中二氢吡啶含量的分析方法。方法样品经乙腈超声提取、高速离心后旋蒸浓缩,以乙腈和超纯水为流动相,采用高效液相色谱-二极管阵列检测器对固体饲料中二氢吡啶进行检测。结果二氢吡啶在0.26~140μg/m L浓度范围内线性关系良好(r~20.999),回收率在81.6%~94.6%之间,相对标准偏差为0.3%~4.0%,方法检出限为0.04 mg/kg。结论本方法具有前处理简便、准确度高、精密度高和可靠性好等优点,可适用于畜禽饲料、水产饲料等常温下为固态的饲料基质中二氢吡啶的检测。     

固相萃取-高效液相色谱法测定饼干中的维生素B12

目的建立固相萃取-高效液相色谱法测定饼干中维生素B12的分析方法。方法样品中的维生素B12用0.1mol/L乙酸钠溶液(pH=4.5)提取,二乙烯苯和N-乙烯基吡咯烷酮共聚物(N-vinylpyrrolidonecopolymer)HLB固相萃取柱净化, 10%的乙腈水溶液定容后用高效液相色谱仪测定。结果维生素B12含量在0.5～10 mg/L线性关系良好,线性相关系数r=0.9999,检出限为0.1 mg/kg。在精密度实验中,相对标准偏差为0.74%～3.75%,在0.3、0.8、1.7mg/kg的添加水平下,加标回收率为93.9%～99.4%。结论该方法准确、高效,适合饼干中维生素B12的测定。     

最佳进给速度

任何制造方法的目标是在最低的材料、能源、设备和工时消耗下,从销售产品中取得最高收入。在木材加工工业中,当锯割木材时,下列参数在使用时特别重要,它在机器与机器之间可能有很大的变化:     

Weather influences feed intake and feed efficiency in a temperate climate

A key goal for livestock science is to ensure that food production meets the needs of an increasing global population. Climate change may heighten this challenge through increases in mean temperatures and in the intensity, duration, and spatial distribution of extreme weather events, such as heat waves. Under high ambient temperatures, livestock are expected to decrease dry matter intake (DMI) to reduce their metabolic heat production. High yielding dairy cows require high DMI to support their levels of milk production, but this may increase susceptibility to heat stress. Here, we tested how feed intake and the rate of converting dry matter to milk (feed efficiency, FE) vary in response to natural fluctuations in weather conditions in a housed experimental herd of lactating Holstein Friesians in the United Kingdom. Cows belonged to 2 lines: those selected for high genetic merit for milk traits (select) and those at the UK average (control). We predicted that (1) feed intake and FE would vary with an index of temperature and humidity (THI), wind speed, and the number of hours of sunshine, and that (2) the effects of (1) would depend on the cows' genetic merit. Animals received a mixed ration, available ad libitum, from automatic feed measurement gates. Using >73,000 daily feed intake and FE records from 328 cows over 8 yr, we found that select cows produced more fat- and protein-corrected milk, and had higher DMI and FE than controls. Cows of both lines decreased DMI and fat- and protein-corrected milk but, importantly, increased FE as THI increased. This suggests that improvements in the efficiency of converting feed to milk may partially offset the costs of reduced milk yield owing to a warmer climate, at least under conditions of mild heat stress. The rate of increase in FE with THI was steeper in select cows than in controls, which raises the possibility that select cows use more effective coping tactics. This is, to our knowledge, the first longitudinal study on the effects of weather on FE. Understanding how weather influences feed intake and efficiency can help us to develop management and selection practices that optimize productivity under unfavorable weather conditions. This will be an important aspect of climate resilience in future.     

Temporal feed restriction and overstocking increase competition for feed by dairy cattle

Dairy cows are often overstocked. Some managers are now using “slick bunk” (i.e., feeding for 0% orts) management to save on feed costs, but this reduces the time that cows have access to feed. Both practices may increase competition and affect feeding behavior in dairy cows. The aim was to determine the effects of temporal and spatial restrictions on the feeding and competitive behavior of group-housed cows. Treatments were 2 levels of stocking (2:1 versus 1:1 cows:feed bin) and 2 levels of feed access time (14 versus 24 h/d access). Eight groups (each of 6 cows) were tested on each of the 4 treatment combinations for 1 wk, with treatment order assigned using a replicated 4 × 4 Latin square design. Dry matter intake (DMI), feeding time, and feeding rate were measured for the last 4 d of each week, and data were summarized daily and for the 2-h period immediately after the morning feeding. Displacements were recorded for 2 h after the delivery of morning feed (peak feeding period) and 2 h following the afternoon milking. The DMI did not decline when temporal access was restricted (27.0 vs. 25.7 ± 0.5 kg/d), and was not affected by overstocking (26.4 ± 1.9, mean ± SD). Cows with restricted temporal access spent less time feeding (190.9 vs. 207.9 ± 6.1 min). Overstocked cows that were temporally restricted had greater feeding rates during the day (156 vs. 137 ± 4 g/min) and especially during the peak feeding period (175 vs. 146 ± 4 g/min) compared with cows that were not restricted. In the peak feeding period, overstocked cows had reduced DMI (3.0 vs. 3.4 ± 0.1 kg/h) and feeding times (20.8 vs. 25.8 ± 1.0 min/h) and increased feeding rates (161 vs. 138 ± 4 g/min). Cows with restricted temporal access had greater DMI (3.9 vs. 2.6 ± 0.2 kg/h) and time spent feeding (27.3 vs. 19.2 ± 1.3 min/h) during the peak feeding period compared with cows that had continuous access to feed. Restricting temporal access in conjunction with overstocking resulted in the greatest increase in daily displacements (15.0 vs. 3.8 ± 1.4 displacements/d); the majority of these occurred during the peak feeding period. Adequate space and time to access feed is essential to minimize feed bunk competition in indoor group housing systems.     

使用饲料添加剂要注意其拮抗作用

列举了生产中常用的几种添加剂在使用过程中可能发生的拮抗作用，并对此提出了有效建议。     

Risk of cross-contamination due to the use of antimicrobial medicated feed throughout the trail of feed from the feed mill to the farm

The cross-contamination of non-medicated feed with residues of antimicrobials causes an animal and public health concern associated with the potential for the selection and dissemination of resistance in commensal bacteria and potentially zoonotic bacteria. To identify the extent of this situation, we built a risk model that provides a way to estimate the percentage of cross-contaminated feed in total and at the different levels at which cross-contamination may occur (i.e. the feed mill, the transport truck, the farm), for different levels of antimicrobial medicated feed produced in a country per year. The model, estimated that when antimicrobial medicated feed represents a hypothetical x_i = 2% of the total feed produced in a country per year, then 5.5% (95% CI = 3.4%; 11.4%) of the total feed produced in a year could be cross-contaminated with different levels of antimicrobials due to practices related to medicated feed. In detail, 1.80% (95% CI = 0.2%; 7.7%) of the total feed produced in such a country would be cross-contaminated due to antimicrobial carryover occurring at the feed mill level, 1.83% (95% CI = 1.3%; 2.0%) at the transport truck level and 1.84% (95% CI = 1.2%; 2.0%) at the farm level. The model also demonstrated that even in cases where antimicrobial medicated feed would be produced in end-of-line mixers or a fine dosing system on trucks, the risk of cross-contamination would not be negligible; the percentage of cross-contaminated feed produced in a country (where x_i = 2%) per year would be 3.7% (95% CI = 2.9%; 4.0%) and 2.4% (95% CI = 1.6%; 2.7%), respectively. It is hard to reduce the risk to zero as it is the result of factors occurring at different levels. Thus, the use of antimicrobial medicated feed should be avoided as much as possible to reduce selection pressure.     

香蕉皮发酵饲料的研究

以香焦皮为主要原料,并添加少鼠尿素、甘薯粉和麸皮.将其混合后,调节水分,经过双螺杆挤压机挤压膨化,得到的产品,再接种一定量的产朊假丝酵母进行发酵.通过对尿素添加量、甘薯添加量、麸皮添加量、接种量和发酵时间对发酵饲料粗蛋白含量的影响进行研究,在单因素试验的基础上,采用4因素3水平的正交试验,确定了挤压香焦皮最适的发酵工艺为:尿素添加量3%、甘薯添加量10%、麸皮添加量25%、接种量10%,发酵时间3d.发酵后的饲料蛋白含量达到27.87%,可以有效地提高饲料中蛋白含量,用于生产蛋白饲料.     

The effects of feed bunk competition on the feed sorting behavior of close-up dry cows

The objectives of this research were to describe the feed sorting, feeding behavior, and feed intake of cows consuming a close-up ration and to determine if these behaviors are affected by competition for access to the feed bunk. Thirty-six dry Holstein cows, consuming a close-up total mixed ration diet, were assigned to 1 of 2 treatments: 1) noncompetitive (1 cow/feed bin) or 2) competitive (2 cows/feed bin). Dry matter intake, feeding behavior, and sorting behavior were monitored for each feed bin on 4 separate days during wk 2 and 3 before the anticipated calving dates of the cows. Fresh feed and orts were sampled daily from each bin and were subjected to particle size analysis. The particle size separator consisted of 3 screens (18, 9, and 1.18 mm) and a bottom pan resulting in 4 fractions (long, medium, short, and fine). Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. Regardless of treatment, the cows sorted against long particles and for short and fine particles. Competition at the feed bunk had no effect on the sorting behavior, dry matter intake, or feeding time of the cows, but did dramatically increase the feeding rate of the cows. The competitively fed cows also had fewer meals per day, and tended to have larger and longer meals. Our results suggest that increased competition at the feed bunk promotes feeding behavior patterns that will likely increase the between-cow variation in composition of total mixed ration consumed.     

Aflatoxin contamination in shrimp feed and effects of aflatoxin addition to feed on shrimp production

One hundred fifty samples of shrimp feed were collected from the eastern and southern regions of Thailand, and aflatoxins B1, B2, G1, and G2 (AFB1, AFB2, AFG1, and AFG2) in them were analyzed. AFB1 contamination ranged from a nondetectable level (< 0.003 ppb) to 0.651 ppb. Metabolites of AFB1 were less abundant than AFB1. To study the effects of aflatoxin in feed on shrimp production, black tiger shrimp were divided into four groups of 30 shrimp per group, tested in triplicate, and fed diets containing 0 (control), 5, 10, or 20 ppb of AFB1 for 10 consecutive days. After 7 or 10 days of consumption on each diet, the shrimp were weighed and sacrificed for laboratory examination. AFB1 and its metabolites were not detected in shrimp muscle. The mortality rate was slightly higher in the AFB1-treated groups than in the control group. The body weight of the surviving shrimp was decreased to 46 to 59% of the initial body weight in the AFB1-treated groups but not in the control group. Histopathological findings indicated hepatopancreatic damage by AFB1 with biochemical changes of the hemolymph. These results show that aflatoxin contamination in shrimp feed may cause economic losses by lowering the production of shrimp. Feed contaminated at the level of 20 ppb or lower (i.e., at the observed natural contamination level) may pose a very low risk, if any, to human health.