牛奶中抗生素残留规律研究

为了解新疆地区奶牛生产中常用抗生素类药物在牛奶中的残留情况,本试验按照新疆地区奶牛生产中抗生素类药物的使用方法及剂量进行投放,并采集牛奶样品进行检测。结果表明,青霉素钾在牛奶中的残留规律为：停药1d〉5d〉3d;头孢噻呋钠为：停药3d〉5d〉1d;链霉素为：停药1d〉3d〉5d;长效土霉素在牛奶中的残留量在停药1～11d一直维持在175μg／kg左右。本试验中除了长效土霉素外,其他药物的残留量均低于中国和欧共体（EEC）规定的标准残留限量。     

Evaluation of certification in the Milk and Dairy Beef Quality Assurance Program and associated factors on the risk of having violative antibiotic residues in milk from dairy farms in Michigan

OBJECTIVE: To determine whether certification in a Milk and Dairy Beef Quality Assurance Program (MDBQAP) was associated with a reduced risk of having antibiotic residues in milk and to define specific management factors that may have predisposed dairy farms to having violative antibiotic residues in milk. SAMPLE POPULATION: 124 dairy farms in Michigan that had > 1 violative residue in milk during 1993 and 248 randomly selected control farms in Michigan that did not have violative residues in milk during 1993. PROCEDURE: A pretested structured questionnaire was mailed to case and control farms. A conditional multivariate logistic regression model was developed to determine risk factors associated with having a violative antibiotic residue in milk. RESULTS: Certification in the MDBQAP did not significantly reduce the risk of having a violative antibiotic residue. Annual treatment of > 10% of a herd for metritis was associated with a reduced risk of having a violative residue. Evidence suggested that a routine request for a milk processor to perform residue testing was associated with a decreased risk of having had a violative antibiotic residue, but routine on-farm residue testing was associated with an increased risk of having had a residue. CONCLUSIONS AND CLINICAL RELEVANCE: MDBQAP certification was associated, although not significantly, with a reduced risk of having violative antibiotic residues in milk. Risk factors significantly associated with violative antibiotic residues are addressed by various critical control points in the MDBQAP and may be indicators for strengths and weaknesses of MDBQAP.     

乳房淋巴结内注射胸腺五肽治疗奶牛隐性乳房炎的研究

将患隐性乳房炎的奶牛30头随机分为5组,3个试验组奶牛分别在乳房淋巴结内注入低、中、高剂量的胸腺五肽（TP-5）;阳性药物对照组奶牛在乳房内灌注＂乳炎＂（主要含林可霉素和新霉素）;空白对照组,不作任何处理。治疗前和治疗后1、2、3周采集奶样进行细菌学检查和体细胞计数（SCC）。停药后4d之内每天采样进行牛奶抗生素残留检测。结果表明,和空白对照组比较,经药物治疗后各组感染乳区有不同程度减少,牛奶SCC减少的幅度依次为阳性药物对照组〉TP-5高剂量组〉TP-5中剂量组〉TP-5低剂量组。＂乳炎＂治疗组在停药后3d之内可以在牛奶中检测到抗生素残留,而TP-5则没有。因此,TP-5对奶牛隐性乳房炎具有治疗作用,并且不会在牛奶中造成有害的残留。     

Use of the food animal residue avoidance databank

In its extra-label drug use policy, the FDA states, as one of the criteria for permitting extra-label drug use, that a significantly extended time period be assigned for drug withdrawal prior to marketing meat, milk or eggs. The phrase "significantly extended time period" is taken to mean, at minimum, the amount of time necessary for any drug residues to deplete to subtolerance levels; however, determination of this period is left to the discretion of the veterinarian responsible for the extra-label drug use. The extended period will vary for each drug, dose, species, and route of administration. Therefore, it is unrealistic to assume that the practitioner can make a rational determination of extended drug withdrawal times without more information than is available through textbooks and professional journals. FARAD was specifically designed to provide veterinarians with the information required to determine extended withdrawal times, and thus prevent residues when drugs are used in an extra-label manner. FARAD can provide valuable residue avoidance assistance to veterinarians when drugs are administered in an extra-label manner, but it is not the answer to the national drug residue problem. Most residues result from failure to observe label-recommended withdrawal times, whereas less than 20% are thought to result from extra-label drug use. A substantial armamentarium of approved drugs is available to the veterinarian to treat most diseases in beef cattle, swine, and broiler chickens; thus, extra-label drug use in these species is unnecessary under most conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence of antimicrobial residues in raw table eggs from farms and retail outlets in Enugu State,Nigeria

The use of antimicrobial agents in poultry production results in their accumulation in the body tissues and products such as milk and egg. The subsequent accumulation of these drugs and their metabolites in body cells is known as drug residue. This study was designed to determine the prevalence of antimicrobial residues in eggs from poultry farms and retail outlets in Enugu State, Nigeria. Eggs from 25 selected commercial farms and ten retail outlets were screened for the prevalence of antimicrobial residue. Also, structured questionnaires were administered to 25 commercial farms in the state to determine the management practices and the most widely used antimicrobial drugs in farms and possible association between the management practices and the occurrence of antimicrobial residues in eggs from these farms. All the 25 farms surveyed use oxytetracycline. Eggs from nine of the surveyed farms tested positive for antimicrobial residue and three of the ten surveyed farms also tested positive for antimicrobial residue. No association was observed (p 0.05; Fisher’s exact test) between the occurrence of antibiotic residues in eggs and farm size, feed source and housing systems. This study was able to demonstrate the presence of antimicrobial residues in eggs destined for human consumption. Drugs like nitrofurans which has been banned for use in food animals are still very much in use in Enugu State, Nigeria. Antibiotics given as feed additives may give rise to drug residues in food animals.     

Farming practices in Sweden related to feeding milk and colostrum from cows treated with antimicrobials to dairy calves

Background

Milk produced by cows in receipt of antimicrobial therapy may contain antimicrobial residues. Such antimicrobial-containing waste milk must be withdrawn from human consumption and is therefore sometimes used as calf feed. Unfortunately, this approach might promote selection of antimicrobial resistant bacteria in the calves’ intestinal microbiota. The objectives of this study were therefore to obtain an overview of waste milk feeding practices on Swedish dairy farms and to investigate if these practices were associated with certain farm characteristics. A representative group of 457 Swedish dairy farmers participated in a web-based survey with questions about the use of colostrum and milk from cows treated with antimicrobials at dry off or during lactation, respectively, as calf feed.

Results

Colostrum (milk from the first milking after calving) and transition milk (milk from the second milking to the fourth day after calving) from cows treated with antimicrobials at dry off was fed to calves on 89% and 85% of the farms in the study, respectively. When antimicrobial therapy was given to cows during lactation, 56% of the farms fed milk that was produced during the course of treatment to calves, whereas milk that was produced during the subsequent withdrawal period was fed to calves on 79% of the farms. Surveyed farmers were less prone to feed such milk if the antimicrobial therapy was due to mastitis than other infections. In Sweden, a majority of antimicrobial treatments during lactation are systemic administration of benzylpenicillin and thus, the bulk of waste milk in Sweden is likely to contain residues of this drug. Feeding waste milk to calves was more common on non-organic farms, and on farms located in Southern Sweden, and was less common on farms with cows housed in cold free stalls barns.

Conclusions

Waste milk that may contain antimicrobial residues is, at least occasionally, used as feed for calves on a majority of surveyed Swedish dairy farms. Future work should focus on the effect of waste milk feeding on the occurrence of antimicrobial resistant bacteria in the calves’ intestinal microbiota.     

Screening food-borne and zoonotic pathogens associated with livestock practices in the Sumapaz region,Cundinamarca, Colombia

Hazardous practices regarding antibiotics misuse, unsanitary milking procedures, and the commercial sales of raw milk and unpasteurized dairy products are currently being practiced by livestock farmers in the Sumapaz region (Colombia). The purpose of this study was to screen for food-borne and zoonotic pathogens associated with local livestock practices. We evaluated 1098 cows from 46 livestock farms in the Sumapaz region that were selected by random. Of the total population of cattle, 962 animals (88%) were tested for bovine TB using a caudal-fold tuberculin test and 546 (50%) for brucellosis by a competitive ELISA. In the population tested, 23 cows were positive for Brucella sp. representing a 4.2% seroprevalence and no cases of bovine tuberculosis were found. In addition, food-borne contamination with Escherichia coli and Staphylococcus aureus was assessed together with antibiotic susceptibility for ten different antibiotics in milk samples from 16 livestock farms. We found that 12 of the farms (75%) were contaminated with these food-borne pathogens. Noteworthy, all of the isolated pathogenic strains were resistant to multiple antibiotics, primarily to oxytetracycline and erythromycin. Our findings suggest that livestock products could be a source of exposure to Brucella and multidrug-resistant E. coli and S. aureus strains as a result of unhygienic livestock practices in the Sumapaz region. Training in good farming practices is the key to improving safety in food production.     

呼和浩特地区牛乳及其乳制品中兽药残留现状调查

旨在了解呼和浩特地区牛乳及其乳制品中兽药残留现状。采用现场调查、问卷调查等方法,调查了65家经销奶产品超市及60家奶产品特产经销店乳制品的销售情况,调查了139名呼和浩特市市民对牛乳及其乳制品的食用情况;调查了35个牛场驻场兽医及10名相关专家在临床上的兽药使用现状。采用回顾性调查方法,调查了2014—2015年内蒙古有关权威部门采用LC-MS-MS、ELISA等方法对呼和浩特地区370份牛乳进行兽药残留检测的结果。采用HPLC方法,检测了呼和浩特地区74份牛乳制品样本中的兽药残留。调查结果显示,呼和浩特市被调查的对象中96.41%的消费者食用牛乳及其乳制品,56.11%的消费者关注乳制品中兽药残留问题;呼和浩特地区牛乳总销量的94.46%来自于呼和浩特地区奶牛场,5.54%来自于其他地区;94.44%的牛场有专职兽医;20%的被调查牛场有超量使用兽药的情况,85.71%的被调查牛场有用药记录,94.29%的被调查牛场严格执行兽药休药期;100%的牛场对所产牛乳进行抗菌药物检测;目前呼和浩特地区兽医临床最常用的4种抗菌药物分别为青霉素、氨苄西林、阿莫西林及头孢噻呋,其他有庆大霉素、甲硝唑等。实验室检测结果显示,呼和浩特地区2014—2015年生产的牛乳中兽药残留均为阴性,市售乳制品样本中亦未检出残留。呼和浩特各辖区生产、流通的牛乳及其乳制品均符合动物性食品中兽药最高残留限量要求。     

Association between measures of milk quality and risk of violative antimicrobial residues in grade-A raw milk

OBJECTIVE: To determine whether bulk-tank standard plate counts or plate loop counts and bulk-tank somatic cell counts (SCC) were associated with detection of violative antimicrobial residues in milk from dairy cattle. DESIGN: Longitudinal study. PROCEDURE: Information for 1994 through 1997 was obtained from a large milk marketing cooperative that operated in multiple states throughout the northeastern and midwestern United States (16,831 herd-years of information from 6,546 farms) and from the Ohio Department of Agriculture Grade-A Milk Certification Program (12,042 herd-years of information from 4,022 farms). Data were analyzed by use of multivariate logistic regression. RESULTS: For both data sets, odds that a violative antibiotic residue would be detected increased as mean SCC for the herd-year increased. Standard plate counts and plate loop counts were not associated with odds that a violative antibiotic residue would be detected. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study suggested that the odds that a violative antibiotic residue would be found in bulk-tank milk increased as mean SCC for the herd-year increased. This suggests that management practices that would be expected to influence SCC may also influence the risk of antibiotic residue violations.     

Residue persistence in sheep milk following antibiotic therapy

Drug residues in milk supplies may have public health implications and can interfere in the manufacture of dairy products, such as cheese. In Spain, most ewe milk production is destined for cheese making, often using raw milk. This study analyses the main factors influencing antibiotic depletion time in lactating dairy sheep. 42, Manchega ewes were distributed into three groups, each receiving a different treatment (cephalexin intramammary infusion, penicillin G intramuscular, and oxytetracycline intravenous injections). During and after the recommended withdrawal period, milk samples were taken at each milking. A microbiological inhibition test (Brilliant Black Reduction, BRT) was used to screen all samples and antibiotic withholding times were established using a logistic regression model. The response to the BRT method in milk from individual ewes treated showed that the effect of the milking order was significant (P<0.001) with the three antibiotics. However the only influence on milk yield was with the intramammary treatment (P<0.005). The BRT method was found to be very sensitive, particularly to the two beta-lactamic antibiotics.     

Microbiological screening test validation for detection of tylosin excretion in milk of cows with low and high somatic cell counts

Antibiotic residues in milk above tolerance levels interfere with dairy product processing and pose potential health risks to consumers. Residue avoidance programmes include, among other components, the observance of withdrawal times indicated in label instructions. Persistence of antibiotics in milk following treatment is influenced by drug, dosage, route of administration, body weight and mammary gland health status. Compositional changes that take place during intramammary infection (IMI) can affect antibiotic excretion in milk, thus modifying milk withdrawal time. The objectives of this study were to validate sensitivity and specificity of a qualitative microbiological method (Charm AIM-96) to detect tylosin in bovine composite milk and to determine the influence of subclinical IMI in tylosin excretion following intramuscular administration. For test validation, two groups of approximately 120 cows were used; one received a single intramuscular injection of tylosin tartrate at a dose of 20 mg/kg, while the other group remained as untreated control. Test sensitivity and specificity were 100% and 94.1% respectively. To determine the influence of subclinical IMI in tylosin excretion, two groups of seven cows, one with somatic cell counts (SCC) < or =250 000 cells/ml and the other with SCC > or =900 000, were administered a single intramuscular injection of tylosin tartrate at a dose of 20 mg/kg. Milk samples were obtained every 12 h for 10 days following treatment. Milk tylosin excretion averaged between 5 and 9 days for cows with low and high SCC respectively (P < 0.0001). Compositional changes in cows with high SCC most likely affect the pharmacokinetic characteristics of tylosin, extending the presence of the antibiotic in milk, thus influencing milk withdrawal times.     

The use of antibiotics on small dairy farms in rural Peru

Very little is known about the use of antibiotics on small dairy farms in lower/middle-income countries. The use of these drugs can have profound impacts on animal health, farmer income and public health. A survey of 156 farmers was conducted in Cajamarca, a major dairy-producing center in the highlands of Peru characterized by small farms (<15 cows) to assess patterns and determinants of antibiotic use and farmers’ knowledge of antibiotics. The reported incidence of disease on these farms was relatively low (0.571 episodes of disease per cow-year), but more than 83% of the reported episodes were treated with antibiotics. The most commonly used antibiotics were oxytetracycline, penicillin and trimethoprim-sulfamethoxazole drugs; antiparasitic drugs were also used to treat what were likely bacterial infections. An increased incidence of treated disease was significantly associated with smaller farm size, lower farmer income, the previous use of the Californian Mastitis test on the farm and antibiotic knowledge. Farmers’ knowledge of antibiotics was assessed with a series of questions on antibiotics, resulting in a “knowledge score”. Increased knowledge was significantly associated with the use of antibiotics for preventative reasons, the purchase of antibiotics from feed-stores, the experience of complications in animals after having administered antibiotics, the number of workers on the farm and the educational level of the farmer. Overall, antibiotics appeared to be used infrequently, most likely because therapeutic interventions were sought only when the animal had reached an advanced stage of clinical disease. Few farmers were able to define an antibiotic, but many farmers understood that the use of antibiotics carried inherent risks to their animals and potentially to the consumers of dairy products from treated animals. The results of this study are useful for understanding the patterns of antibiotic use and associated management, demographic and knowledge factors of farmers on small dairy farms in rural Peru.     

Testing for antibiotic residues in milk

Milk from dairy farms in England and Wales has been tested regularly for antibiotic residues since 1965. The sensitivity of the test organism was 0.02 iu/ml penicillin or equivalent until the change to 0.01 iu/ml in January 1986. In 1984-85, 99.6 per cent of the 2,000,000 milk samples tested passed the test and there was an average of 695 failures per month. From 7500 on-farm investigations over the two years 1983-85 the most frequent reasons suggested by farmers for their test failures were not withholding milk for the full withdrawal period (19.3 to 16.5 per cent) and accidental transfer of milk (16.3 to 16.7 per cent). Lactating and dry cow intramammary antibiotic preparations were held responsible for rather over 50 per cent and 25 per cent respectively of the failures in both years.     

Abusive use of antibiotics in poultry farming in Cameroon and the public health implications

1. The types and methods of use of antibiotics in poultry farms in Cameroon, residual levels and potential microbial resistance were determined.

2. A questionnaire-based survey identified the different antibiotics used and high-performance liquid chromatography (HPLC) was used to determine residual levels of antibiotics.

3. Pathogens were isolated, identified by use of commercial API kits and minimum inhibition concentration (MIC) was determined.

4. Oxytetracyclin, tylocip and TCN (oxytetracycline, chloramphenicol and neomycin) were the most frequently used antibiotics. Antibiotics screened by HPLC were chloramphenicol, tetracycline and vancomycin. All of them except vancomycin were detected, and the concentration of these antibiotics was higher than the maximum residual limits (MRL) set by regulatory authorities.

5. No residues of various antibiotics were found in egg albumen or yolk. The concentration of tetracycline was significantly higher in liver (150 ± 30 µg/g) than in other tissues.

6. Foodborne pathogens, including Salmonella spp., Staphylococcus spp., Listeria spp., Clostridium spp. and Escherichia spp., were identified. Most of the pathogens were resistant to these various antibiotics tested.

7. These findings imply the need for better management of antibiotic use to control sources of food contamination and reduce health risks associated with the presence of residues and the development of resistant pathogens by further legislation and enforcement of regulations on food hygiene and use of antibiotics.

     

Intramammary application of ozone therapy to acute clinical mastitis in dairy cows

The infusion of ozone into the inflamed quarter of cows with clinical mastitis was performed and the efficacy of ozone therapy was evaluated. Ozone was infused into the inflamed quarter via a teat canal using ozone gas generating equipment. Nineteen Holstein cows with acute clinical mastitis were divided into two groups: 15 cows treated with ozone therapy, and 4 cows treated with antibiotic therapy. Systemic and local clinical signs, California Mastitis Test scores, the mastitis causing pathogens, electronic conductivity of milk, and somatic cell counts in milk from ozone- and antibiotic-treated quarters, were compared between the groups. Sixty percent (9/15) of cows with acute clinical mastitis treated with ozone therapy, did not require any antibiotics for recovery. This newly developed ozone therapy method was proven to be effective, safe, and cost effective, and carries no risk of drug residues in milk.     

Depletion of gentamicin in the milk of Holstein cows after single and repeated intramammary and parenteral treatments

Twenty-four healthy Holstein cows, 2.72 ± 0.64 (mean ± SD) years old, weighing 603.96 ± 73.22 kg (mean ± SD), and representing various levels of milk production, were used to determine the depletion of gentamicin (GT) in milk. The cows had not received antibiotics or other drugs that could interfere with study for at least 60 days before the beginning of the investigation. The cows were divided into six groups (n = 4) and treated with single (treatments A, B and C) or repeated (treatments D, E and F) doses of GT. Cows were acclimated for 7 days before administration of GT and milked twice a day at 12-h intervals (06.00 hours, 18.00 hours) throughout the duration of the study. Control milk samples were obtained after the arrival of the cows and assayed to establish their GT free status. On day 1 of each treatment, a baseline milk sample was collected from the milk produced (06.00 hours) by each cow. A single dose of GT was administered intramammarlly (A, i.m.m. left front quarter, 500 mg), intravenously (B, i.v., 5 mg/kg body weight) or intramuscularly (C, i.m., 5 mg/kg body weight). Cows in treatments D (i.m.m., 500 mg), E (i.v., 5 mg/kg body weight) and F (simultaneous i.m.m. 500 mg plus i.v. 5 mg/kg body weight) were treated twice a day for 5 consecutive days just after the morning and evening milkings. Milk samples from individual cows were collected every day after each milking during and after dosing until GT concentration in the milk was below the safe level of ± 30 ng/mL. The concentration of GT in milk was determined by a high-performance liquid chromatographic procedure. Depletion of GT to a concentration ± 30 ng/mL occurred at the seventh (84 h), third (36 h), third (36 h), eleventh (132 h), third (36 h) and nineteenth (228 h) post-dosing milking, for cows in treatments A, B, C., D, E and F respectively. The highest mean ± SEM) concentrations of GT were 14 710 ± 1213.89, 167.87 ± 46.94 and 91.62 ± 14.55 ng/mL measured in the first milking post dosing (12 h) for cows in treatment A, B and C respectively; for cows in treatments D, E and F, during the dosing period, they were 14067.50 ± 2989.09, 446.07 ± 100.92, and 22900 ± 2843.66 ng/mL and occurred at the seventh, third and eighth milking respectively. Because GT is not approved for use in dairy cattle and because of the long depletion time associated with some possible treatments, illegal and extra-label use is likely to cause residues in milk.     

Evaluation of enzyme-linked immunosorbent assays performed on milk and serum samples for detection of neosporosis and leukosis in lactating dairy cows

Serum and milk samples from 1229 cows on 22 Ontario dairy farms were individually tested for antibodies specific for bovine leukosis virus (BLV) and Neospora caninum by enzyme-linked immunosorbent assay (ELISA). Antibodies against BLV were present in 361 serum samples (29.4%) and 369 milk samples (30.0%). Comparing the 2 tests, agreement was almost perfect (k = 0.86; 95% CI = 0.83 to 0.90) and the proportions of samples positive were not significantly different (P = 0.56). Both tests identified the same 3 herds free of bovine leukosis virus. Antibodies against N. caninum were detected in 138 serum samples (11.2%), and 111 milk samples (9.0%). Agreement between the 2 tests was moderate (k = 0.52; 95% CI = 0.43 to 0.59). Four herds were free of neosporosis by the serum test, while 10 herds were negative by the milk test. The ELISA on milk samples facilitates sample collection to classify herds free of BLV; the milk N. caninum ELISA was less reliable in predicting herd-level infection.     

Antibiotic residues in milk following bulbar subconjunctival injection of procaine penicillin G in dairy cows

OBJECTIVE: To determine whether, and at what time, penicillin enters milk at a concentration that is detectable following bulbar subconjunctival injection in lactating dairy cows. DESIGN: Randomized clinical trial. ANIMALS: 66 Holstein cows that were at least 2 weeks past calving and had not been treated with antibiotics in the preceding 30 days. PROCEDURE: Cows were randomly assigned to receive a treatment of 1 ml (300,000 units) procaine penicillin G by bulbar subconjunctival injection or remain untreated. Composite milk samples were collected immediately before treatment and 4, 10, 16, 22, 28, and 40 hours after treatment. Milk samples were tested by use of a commercial test for beta-lactam antibiotics. RESULTS: Among penicillin-treated cows, the first positive test results were observed 4 hours after treatment, and the last positive result was observed 22 hours after treatment. The percentages of positive test results before treatment and at 4, 10, 16, 22, 28, and 40 hours after treatment were 0, 9, 87, 42, 8, 0, and 0%, respectively. None of the untreated cows had positive test results for beta-lactam antibiotics at any sampling time. CONCLUSIONS AND CLINICAL RELEVANCE: Penicillin was detected in milk for up to 22 hours after a single subconjunctival injection of procaine penicillin G in cows. This result should be considered when recommending milk withholding periods following the administration of penicillin by this route in lactating dairy cows.     

Vaccination using phase I vaccine is effective to control Coxiella burnetii shedding in infected dairy cattle herds

The effectiveness of the vaccination of dairy cows combined or not with antibiotics (i.e. oxytetracycline) to control Coxiella burnetii (Cb) shedding at herd level was investigated in 77 Q fever clinically affected herds. In addition to nulliparous heifers’ vaccination, one out of the four following medical strategies was randomly assigned to dairy cows in each herd: vaccination (using a phase I vaccine) alone, vaccination combined with oxytetracycline, oxytetracycline alone or nothing. Their effectiveness to reduce Cb load in quarterly samples of bulk tank milk (BTM) and of pooled milk of primiparous (MP) was assessed through logistic hierarchical models. A significant reduction in Cb load was observed in herds where the vaccination of ≥80% of dairy cows was implemented; whereas the use of antibiotics was uneffective. Our findings support the interest of a whole vaccination strategy and provide evidence for decreasing the use of antibiotics in dairy cattle herds.