乳品安全中的牛乳过敏

牛乳过敏是婴幼儿中一种常见的食物过敏,严重危害婴幼儿健康。对牛乳过敏的机理、牛乳中的过敏原成分、牛乳过敏原的检测、加工对牛乳过敏原的影响作了详细的介绍。     

Management,operational, animal health,and economic characteristics of large dairy herds in 4 states in the Upper Midwest of the United States

Recent trends in dairy farm structure in the United States have included a decreasing number of farms, although farm size has increased, especially the share of milk production from very large herds (>2,500 cows). The objectives of this observational study were to describe common management practices; to characterize labor and operational structure; to measure some aspects of animal health, including lameness, hock lesions, mortality, and mastitis incidence; and to summarize cost of production on farms with more than 2,500 cows in 4 states in the Upper Midwest of the United States. The study included 15 dairy farms in Minnesota, Wisconsin, Iowa, and South Dakota. Farms were visited twice, once each year, and on-farm herd records were collected for those 2 yr. On-farm herd records were used to investigate mortality, culling, pregnancy rate, and clinical mastitis incidence. At least 1 high-producing pen of mature cows and 1 pen of fresh cows were scored for locomotion. Likewise, at least 1 pen of high-producing mature cows was scored for cleanliness and hock lesions. Median herd size was 3,975 cows (range = 2,606–13,266). Milk sold per employee was 1,120,745 kg and the number of cows per employee was 105. Eighty percent of the farms had Holstein cows, 13% had Jersey, and 7% had Jersey-Holstein crosses. All farms used artificial insemination as the sole form of breeding and 100% of the farms used hormonal synchronization or timed artificial insemination programs in their reproductive protocols; 21-d pregnancy rate was 21.7%. Median lameness prevalence was 18.3% and median severe lameness prevalence was 5.1%. Median hock lesion prevalence was 17.4% and median severe hock lesion prevalence was 1.9%; mortality rate was 7.4%. Clinical mastitis incidence was 62.5 cases per 100 cow-years. Feed costs accounted for approximately 53% of the total cost of producing milk, followed by labor at 11%, interest and depreciation expenses at 10%, and replacement costs at 9.5%. Herds in the top 50th percentile for profitability had a net income of $2.40 per hundredweight of milk sold compared with $0.95 per hundredweight for herds in the bottom 50th percentile. Although results of this study were helpful in understanding how large dairy systems operate in the Upper Midwest, more research is yet needed with a larger number of farms and wider variety of management practices to identify factors within these large farms that promote optimal animal health and profitability.     

乳与乳制品中四种动物源性成分鉴定方法的研究

目的 针对小众乳与乳制品的掺假的现象,构建乳与乳制品中动物源性成分检测方法。方法 设计合成了牛、羊、驴、水牛的特异引物探针,优化乳与乳制品中核酸提取方法,对设计的荧光PCR方法进行了特异性、灵敏度、适用性进行验证。结果 该方法对于常见动物物种具有较强特异性和灵敏度,牛、羊、驴、水牛的检测灵敏度分别为0.001、0.01、0.01、0.01 ng。此外,该方法适用性较强,在各类乳与乳制品样品中均能检出标识动物源性成分和掺伪动物源性成分。结论 本研究构建的检测方法,特异性、灵敏度、检出限等指标均能满足日常实验需要,可为监管与检验提供有力的技术支撑。     

我国乳品质量安全的影响因素分析

近年来,国内外乳品质量安全事件频发,乳品质量安全问题引起社会各界的高度关注。本文通过对乳品供应链中产、加、销各环节的研究,分析影响我国乳品质量安全的因素,并提出相应的对策建议,对提高乳品质量安全以及保证人们的身体健康和生命安全具有十分重要的意义。     

Environment,nutrition, and management practices for far-off,close-up,and fresh cows on Canadian dairy farms—A retrospective descriptive study

The complex and interrelated management components of dairy farming are associated with health, production, and profitability of the herd, yet there is limited objective data on current management practices of the far-off, close-up, and fresh periods across Canadian dairy farms. We aimed to describe management practices of Canadian dairy farms by using a pre-existing risk assessment tool and outline potential management opportunities. Upon veterinarians' or producers' request, a transition management risk assessment (The Vital 90, Elanco) was performed by trained observers (n = 10) during farm visits (n = 78) between August 2014 and March 2018. Most farms were in Ontario (n = 64), whereas the remaining were in Alberta (n = 5), British Columbia (n = 4), Manitoba (n = 1), Prince Edward Island (n = 2), Newfoundland (n = 1), and Saskatchewan (n = 1). The study included 79 questions about nutrition, pen management, and cow comfort of the dry (approximate ranges: far-off, ?60 to ?20 d in milk; close-up, ?20 to 0 d in milk) and fresh (0–30 d in milk) periods. The herds averaged 125 milking cows, and most had 2 defined dry groups (81%). Freestall (FS; 54%) and straw-bedded loose pack (BP; 81%) were the most common housing systems observed in the far-off and close-up periods, respectively. Heifers and cows were housed together in 56, 80, and 59% of the far-off, close-up, and fresh pens, respectively. A large proportion of the far-off (FS: >100% stocking density; BP: <9.3 m²/cow; 41%), close-up, and fresh pens (FS: >80% stocking density; BP: <13.9 m²/cow; 52 and 49%, respectively) were overstocked. Poor water access was observed across all periods (65, 58, and 24% of the far-off, close-up, and fresh, respectively). Only a few farms had proper heat abatement systems in place (absence of properly functioning soakers or fans; <10% in the dry and 15% in the fresh periods). Cows were able to sort their ration in 60% of the dry period pens and 31% of the fresh pens. In 73% of the farms, fresh cow health monitoring protocols were not in place. Colostrum cows and sick cows were housed together in 40% of the farms; 59% separated the newborn from the dam within 2 to 12 h of birth with colostrum harvested immediately thereafter. This work describes prevalent management practices in the dry and fresh periods and highlights areas for potential improvement. Future research should focus on the associations between management choices and health performance of dairy farms.     

Functional milks and dairy beverages

During the last decade, consumers' approach to healthy foods has changed dramatically, and today enhancing the health span of consumers through consumption of healthy food is more important than simply enhancing their life span. Rising medical costs are the prime factor forcing people to find cheaper and effective means of protecting their health. This fact has led to an increase in consumers' interest in functional foods. Dairy products occupy a significant space in the functional foods market and dairy-based functional beverages are a growing segment of this sector. This article reviews recent scientific, technological and commercial developments in the functional dairy-based beverage sector.     

Calf management risk factors on dairy farms associated with male calf mortality on veal farms

The objective of this cross-sectional herd-level study was to assess the association of calf management practices on source dairy farms with mortality risk on veal farms. From April to October 2016, 52 source dairy farms supplying male calves to 2 veal operations were visited once. A questionnaire was administered that covered all areas of calf management, calves between 1 and 10 d of age were examined using a standardized health scoring system, and blood was taken to evaluate passive transfer of immunoglobulins. The mortality risk for calves from each dairy farm was calculated based on the number of male calves sold from the dairy farm and that died during 2016 at the veal operations. The mean mortality risk was calculated for both veal farms and, based on the veal facility-adjusted mortality risk, dairy farms were classified as high- or low-mortality source farms. Using the information gathered at the 52 source dairy farms, a logistic regression model was used to assess factors associated with being a high-mortality source farm. Suppliers to veal farm 1 had a mean mortality risk of 9.6% and suppliers to veal farm 2 had a mean mortality risk of 4.2%. The lower mortality risk at veal farm 2 was partially influenced by a shorter period of observation. Of the 182 calves examined during the single visit to the source dairy farms, 41% of male calves and 29% of female calves had at least one identifiable health abnormality. The risk of failure of passive transfer on source dairy farms was low, with only 13% of calves tested having <10 mg of IgG/mL of serum. The subset of calves examined at the source dairy farm was not followed prospectively to the veal farms. Using a tube feeder or pail to feed colostrum, bedding male calves on wood shavings or chopped straw at the source dairy farm, and the herd veterinarian not routinely and actively inquiring about the health and performance of calves during regular herd visits were significantly associated with the farm being classified as a high-mortality source dairy farm. Checking the calving pen at an interval of every 3 h or more during the day was associated with a lower probability of being classified as a high-mortality source dairy farm. The results of this study suggest that there are management practices on the source farm that contribute to the risk of mortality on veal farms.     

The Canadian National Dairy Study 2015—Adoption of milking practices in Canadian dairy herds

Several studies have investigated which management practices have the greatest effect on udder health, but little information is available on how broadly the recommended milking practices are adopted across Canada. The National Dairy Study 2015 was designed to gather dairy cattle health and management data on dairy farms across Canada. The objectives of the present study were to describe the current proportions of adoption of milking practices on Canadian dairy farms, and identify factors associated with their use on farms. A bilingual questionnaire measuring use of various practices, including an udder health-specific section, was developed and sent to all Canadian dairy farms. The questions in the udder health section of the questionnaire were adapted from a bilingual questionnaire previously validated and containing questions regarding general milking hygiene and routine, and on-farm mastitis management. Chi-squared tests were used to investigate simple associations between adoption of practices and various explanatory variables including region, milking system, herd size, and bulk tank somatic cell count. In total, 1,373 dairy producers completed the survey. The regional distribution of the participants was representative of the Canadian dairy farm population, and milk quality was, on average, similar to nonparticipants. Overall, Canadian dairy producers followed the recommendations for milking procedures, but some were more extensively used than others. Fore-stripping, cleaning teats, wiping teats dry, using single-cow towels, and use of postmilking teat disinfectant were widely adopted. Use of gloves and glove hygiene, use of a premilking teat disinfectant, and use of automatic takeoffs were not as extensively implemented. Adoption percentages for several practices, including use of gloves, use of a premilking teat disinfectant, teat drying methods, and use of automatic takeoffs were significantly associated with milking system, herd size, and region. It would be helpful to explore the reasons why producers choose to adopt or ignore recommended milking practices as most are easy to include in the routine and are fairly inexpensive.     

Good nutritional practice from producer to consumer

Today we manage food safety through good practices at different levels of food production, distribution, and consumption. The paper analyses current good practices, parameters involved in the food safety circle along the food supply chain, and consumer dilemmas. As a result of the current situation the new approach called "Good Nutritional Practice" (GNP) is proposed to balance the food safety systems. It is shown how important it is to integrate actual the food safety solutions within GNP, which includes consumers, and is based on a model that covers subsystems from other relevant good practices (nine good practices along the food supply chain). It has been shown that present maintenance of food safety in the food supply chain can be easily broken down, because of the different kinds of barriers or a simple misunderstanding among stakeholders including consumers.     

建立乳品质量安全追溯体系的必要性及建议

乳品质量安全追溯体系作为乳品质量安全管理的有效手段,越来越受到有关部门和广大消费者的关注。本文从乳品的重要营养作用、乳品行业的重要经济作用、乳产品的特殊性,以及乳品质量安全追溯体系的重要保障作用等方面论证了建立乳品质量安全追溯体系的必要性,并针对体系建设提出一些政策建议。     

Fixation and Staining Milkfat Globules in Cream for Transmission and Scanning Electron Microscopy

Three methods were evaluated for fixing and staining milkfat globule (MFG) specimens from dairy cream (CREAM) for examination by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). CREAM-agarose gel mixtures were fixed in glutaraldehyde and OsO₄ vapors; treated with a mordant; fixed and stained with imidazole-buffered OsO₄, ferricyanide OsO₄, or tricomplex OsO₄; partially dehydrated; en bloc stained; and embedded and thin-sectioned for TEM, or critical point-dried and mounted on stubs for SEM without metal coating. The three methods exhibited varing degrees of presenting MFG and MFG membranes for visualization by thin-section TEM and SEM.