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1.
Anaerobic digestion is considered as a promising method to manage animal waste with antibiotic‐resistant bacteria. Current research was conducted to investigate the survival of multidrug‐resistant bacteria (MDRB) resistant to three groups of antibiotics: (i) cefazolin, neomycin, vancomycin, kanamycin (group 1); (ii) penicillin, oxytetracycline, ampicillin, streptomycin (group 2); and (iii) cefazolin, neomycin, vancomycin, kanamycin, penicillin, oxytetracycline, ampicillin, streptomycin (group 3), in anaerobic digestion of dairy manure and co‐digestion of dairy manure and waste milk at 37°C and 55°C for 22 days, respectively. The population densities of three groups of MDRB on peptone, tryptone, yeast and glucose agar plates incubated at 30°C for 7 days before and after digestion showed 100% destruction in both digestates at thermophilic temperature. Overall reduction of more than 90% of three groups of MDRB was observed in mesophilic digestion with no significant differences (P > 0.05) between manure and milk mixture. Co‐digestion of dairy manure and waste milk always produced significantly (P < 0.05) higher total gas and methane gas than digestion of manure alone at both temperatures. Gas production in each case was significantly (P < 0.05) higher in thermophilic digestion than in mesophilic digestion. The results demonstrate that thermophilic co‐digestion of dairy manure and waste milk offers more benefits in terms of the environment and economy.  相似文献   

2.
本次调研共收集了华北地区99家奶牛场的用水及粪污处理情况数据进行了分析总结。结果表明,①85.9%的牛场以深井水作为水源,其中61.2%的牛场对用水进行消毒处理,43.5%的牛场安装有水表并记录用水情况。②在牛场用水中,牛的饮水量所占比例最高,达60%以上;其次为挤奶厅用水,约占20%。③夏季牛场头均饮水量、挤奶厅用水量、喷淋用水量均显著高于春秋冬季(P<0.05),夏季的头均总用水量比春秋冬季增加了33%(P<0.01)。随着牛场存栏量的增大,奶牛头均总用水量显著减少(P<0.05)。④年产奶量较高的牛场每产1kg牛奶饮水量、挤奶厅用水量显著降低(P<0.01),致使每千克产奶量的总用水量减少52%(P<0.01),用水效率提高。⑤随着养殖规模的增大,牛场雨污分离设施与干湿分离设施配备率分别显著增至62%、72%(P<0.05,P<0.01)。由此可得,存栏量越大、年产奶量越高,牛场每产1kg牛奶用水量越低,用水效率越高,而且配备的雨污分离设施、干湿分离设施比例越高,这些均有利于减少单位产奶量的粪污产生量及其处理压力。  相似文献   

3.
本研究评估了日粮添加不同水平的废弃咖啡渣对乳山羊瘤胃发酵、泌乳性能和采食行为的影响。试验选择平均泌乳量为(1.2±0.30)kg、平均泌乳天数为(35.5±9.0)d的40头乳山羊,按照体重分为4组,每组10头。对照组浓缩料不添加废弃咖啡渣,处理组日粮废弃咖啡渣添加水平为2%、4%和8%。对照组与处理组补饲的粗饲料为苜蓿草。试验结果:随着日粮废弃咖啡渣添加水平的升高,乙酸、丁酸和乙酸与丙酸比值表现为显著线性升高(P<0.05),而丙酸、异丁酸、戊酸、异戊酸和支链脂肪酸浓度表现为显著线性降低(P<0.05)。乳山羊每天产奶量、乳蛋白质、乳糖量随着废弃咖啡渣水平的升高表现为显著二次曲线升高(P<0.05),同时泌乳占比方面,产奶量也表现为显著的二次曲线升高(P<0.05)。试验期间,乳山羊每天的采食时间随着废弃咖啡渣添加水平的升高显著升高(P<0.05),而反刍时间表现为二次曲线升高趋势(P=0.06)。结论:浓缩料中废弃咖啡渣添加水平不超过10%时,可以改善瘤胃乙酸和丁酸含量,提高乳产量和乳成分。  相似文献   

4.
The objective of this study was to investigate the effect of solid–liquid separation on anaerobic digestion of dairy manure in semi‐continuous stirred tank reactors. Reactors fed with liquid fraction of dairy manure (screened liquid manure) were kept in water baths at mesophilic (Run 1) and thermophilic (Run 3) temperatures, respectively, while reactors fed with water diluted manure and kept at mesophilic (Run 2) and thermophilic (Run 4) temperatures as control reactors. The performances of reactors were compared in terms of biogas and methane production, and digestate characteristics. The methane yields obtained from screened manure were higher than those from diluted manure at both mesophilic and thermophilic temperatures, while the highest methane yield was 185 L/kg VSadded under thermophilic temperature. Solid–liquid separation also had improved the effect on digestate fertilizer characteristics. Among four digestates from reactors, the highest contents of nutrients, N (4.12 g/kg) and P (2.36 g/kg) were found in Run 3, while the highest content of K (3.42 g/kg) was found in Run 1. These results showed the benefits of solid–liquid separation of dairy manure on process performance and digestate characteristics.  相似文献   

5.
Increasing feed costs and the desire to improve environmental stewardship have stimulated renewed interest in improving feed efficiency of livestock, including that of US dairy herds. For instance, USDA cost projections for corn and soybean meal suggest a 20% increase over 2010 pricing for a 16% protein mixed dairy cow ration in 2011, which may lead to a reduction in cow numbers to maintain profitability of dairy production. Furthermore, an October 2010 study by The Innovation Center for US Dairy to assess the carbon footprint of fluid milk found that the efficiency of feed conversion is the single greatest factor contributing to variation in the carbon footprint because of its effects on methane release during enteric fermentation and from manure. Thus, we are conducting research in contemporary US Holsteins to identify cows most efficient at converting feed to milk in temperate climates using residual feed intake (RFI), a measure used successfully to identify the beef cattle most efficient at converting feed to gain. Residual feed intake is calculated as the difference between predicted and actual feed intake to support maintenance and production (e.g., growth in beef cattle, or milk in dairy cattle). Heritability estimates for RFI in dairy cattle reported in the literature range from 0.01 to 0.38. Selection for a decreased RFI phenotype can reduce feed intake, methane production, nutrient losses in manure, and visceral organ weights substantially in beef cattle. We have estimated RFI during early lactation (i.e., to 90 d in milk) in the Beltsville Agricultural Research Center Holstein herd and observed a mean difference of 3.7 kg/d (P < 0.0001) in actual DMI between the efficient and inefficient groups (±0.5 SD from the mean RFI of 0), with no evidence of differences (P > 0.20) in mean BW, ADG, or energy-corrected milk exhibited between the 2 groups. These results indicate promise for using RFI in dairy cattle to improve feed conversion to milk. Previous and current research on the use of RFI in lactating dairy cattle are discussed, as well as opportunities to improve production efficiency of dairy cattle using RFI for milk production.  相似文献   

6.

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.  相似文献   

7.
The aim of this study was to investigate the phenotypic and genotypic diversity and anti‐microbial resistance among staphylococci of dairy herds that originated from Paraiba State, north‐eastern Brazil, a region where such studies are rare. Milk samples (n = 552) were collected from 15 dairy farms. Isolates were evaluated for anti‐microbial susceptibility by Kirby–Bauer disc diffusion method. Confirmation of methicillin‐resistant Staphylococcus aureus (MRSA) was performed using multiplex PCR targeting mecA and nuc genes in addition to phenotypic assay based on PBP‐2a latex agglutination. Clonal relatedness of isolates was determined by pulsed‐field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) genotyping. Staphylococci were detected in 269 (49%) of the samples. Among these, 65 (24%) were S. aureus. The remaining 204 isolates were either coagulase‐negative staphylococci (n = 188; 70%) or coagulase positive other than S. aureus (n = 16; 6%). Staphylococci were cultured in seven (35%) of the 20 hand swab samples, from which five isolates were S. aureus. The isolates were most commonly resistant against penicillin (43%), ampicillin (38%) and oxacillin (27%). The gene mecA was detected in 21 S. aureus from milk and in one isolate from a milker's hand. None of the isolates were resistant to vancomycin. PFGE findings showed high clonal diversity among the isolates. Based on MLST, we identified a total of 11 different sequence types (STs 1, 5, 6, 83, 97, 126, 1583, 1622, 1623, 1624 and 1625) with four novel STs (ST1622‐ST1625). The findings show that MRSA is prevalent in milk from semi‐extensive dairy cows in north‐eastern Brazil, and further investigation on its extent in various types of milk production systems and the farm‐to‐table continuum is warranted.  相似文献   

8.
To examine the effect of storage temperature on the emission of methane (CH4) and carbon dioxide (CO2) and on recovery of nutrients from raw dairy manure slurry (RS) and slurry digested in a methane digester (DS), both slurries were stored in closed 100 L steel tanks under psychrophilic conditions (5, 10, 15 and 20°C) for a 150 day period. As the storage temperature increased, total methane emission increased in both types of slurry. The amount of methane emitted per unit of volatile solids of the RS and DS was 0.19 L/g and 0.10 L/g, respectively. The respective carbon dioxide emissions were 0.20 L/g for RS and 0.12 L/g for DS at 20°C of storage temperature. At temperatures greater than 15°C, the methane concentration in the emitted gas remained more than 40% of the total gas. During the experimental period, in excess of 90% of the total Kjeldahl nitrogen in these slurries was recovered (91.4–93.7% for RS and 93.7–98.4% for DS) after storage, and ammonium nitrogen was recovered in excess of 100% (100.1–143.2% for RS and 106.7–143.2% for DS storage tanks) because of the mineralization of organic nitrogen in the influent. These results indicate that manure slurry characteristics and storage temperature have significant impacts on methane emission. It can be concluded that on typical farms located in northern Japan, methane emission from manure storage tanks during late fall, winter and early spring may be negligible, because of manure temperatures less than 10°C. During late spring, summer and early fall, methane emissions can be substantially reduced by using underground storage to maintain lower manure temperatures.  相似文献   

9.
The spent mushroom substrate of Ganoderma balabacense cultivation (SMSGB) contains a large amount of bioactive substances. However, the potentials of SMSGB for improving milk production in dairy cows have not been thoroughly studied. In this study, the effects of hot water extract (HWE) from spent mushroom substrate after G. balabacense cultivated with JUNCAO, the herbaceous plants long‐known to be suitable for cultivating edible and medicinal fungi, on production performance and hematology parameters of dairy cows, were determined. Holstein dairy cows were fed different doses of HWE. After a 60‐day administration period with 100 g/day of HWE, milk yield, milk protein and triglyceride (TG) levels increased by 4.02% (P < 0.01), 4.49% (P < 0.05) and 32.65% (P < 0.05), respectively; somatic cell count (SCC) and alanine aminotransferase (ALT) were significantly decreased (P < 0.05). The production performance of dairy cows suggests that HWE with SMSGB treatment is effective in improving milk yield (P < 0.01) and hematology parameters of dairy cows, and may be useful as a functional feed additive.  相似文献   

10.
试验旨在研究日粮中添加复合菌培养物对奶牛产奶量、乳品质和体细胞数的影响。选择30头荷斯坦奶牛,分为对照组和试验组,对照组饲喂基础日粮,试验组在基础日粮中添加复合菌培养物400 g/(头·d),试验期为37 d。测定指标包括产奶量、乳脂率、乳蛋白率及体细胞数。结果表明,试验组奶牛产奶量比对照组增加6.84%(P>0.05);乳汁体细胞数下降率比对照组提高29.78%(P<0.05);两组奶牛乳脂、乳蛋白之间无明显差异(P>0.05)。本试验结果表明,复合菌培养物在降低体细胞数和改善奶牛产奶性能方面具有良好的效果。  相似文献   

11.
本试验旨在研究饲粮全棉籽比例对奶牛泌乳性能和乳脂脂肪酸组成的影响.试验采用4×4拉丁方试验设计,选择8头泌乳早期的经产中国荷斯坦奶牛(产奶量、胎次、产犊日期接近,健康无疾病),分为4组,每组2个重复,每个重复1头牛.A组饲喂基础饲粮,B、C和D组分别饲喂含5％、10％、15％全棉籽的试验饲粮.每期试验28 d,其中预试期为7d,正试期为21 d.结果表明:随着饲粮全棉籽比例的增加,奶牛产奶量有提高趋势(P＞0.05),校正乳产量极显著提高(P＜0.01).全棉籽极显著地提高了奶牛的乳脂率(P＜0.01),对乳蛋白率、乳糖率和乳非脂固形物率无显著影响(P＞0.05).全棉籽极显著降低了饱和脂肪酸( SFA)的含量(P＜0.01),不同程度地提高了乳中多不饱和脂肪酸( PUFA)和单不饱和脂肪酸(MUFA)的含量(P＜0.05或P＜0.01);短链脂肪酸和中链脂肪酸含量都显著降低(P＜0.05),长链脂肪酸含量有不同程度的提高(P＜0.05或P＜0.01).结果提示,饲粮中添加全棉籽可以提高奶牛产奶量,优化乳脂脂肪酸组成,改善乳脂品质,并以10％为泌乳早期奶牛最佳饲粮全棉籽比例.  相似文献   

12.
This study was performed in a 2 × 4 factorial arrangement to explore and compare the effects of inclusion of two live Bacillus additives (B. licheniformis and B. subtilis) at four doses (0, 0.25 × 107, 0.50 × 107 and 0.75 × 107 colony‐forming units (cfu)) on in vitro gas production kinetics, fiber degradation, methane production and ruminal fermentation characteristics of maize stover and rice straw by mixed rumen microorganisms in dairy cows. The pH, concentrations of ammonia nitrogen (NH3‐N) and isovalerate were increased (P < 0.05), while the methane (CH4) production, ratio of acetate to propionate, and total volatile fatty acids (TVFA) concentration were decreased (P < 0.05) by the supplementation of B. licheniformis compared with that of B. subtilis. Adding B. licheniformis and B. subtilis raised (P < 0.05) or numerically raised the maximum gas production, while decreasing (P < 0.05) or numerically lowering pH and concentrations of most volatile fatty acids. The addition of B. licheniformis increased (P < 0.05) the NH3‐N concentration but reduced CH4 production and ratio of acetate to propionate (P < 0.05), while the NH3‐N concentration was decreased (P < 0.05), and the CH4 production and ratio of acetate to propionate were increased by that of B. subtilis compared to the control. Results obtained in this research suggest that B. licheniformis would be preferred as a live Bacillus additive in comparison with B. subtilis, and its optimal dose should be 0.25 × 107 cfu/500 mg substrates.  相似文献   

13.
The introduction of biogas plants is a promising way to recycle organic wastes with renewable energy production and reducing greenhouse gas. Application of anaerobic digestate as a fertilizer reduces the consumption of chemical fertilizers. In this study, the survival of pathogenic bacteria and plant growth promoting bacteria (PGPB) in two full‐scale biogas plants operated at mesophilic condition were investigated. Feedstock and anaerobic digestate samples were collected from biogas plants and bacteria load in samples were detected using standard dilution plate method. Pathogenic bacteria were reduced to not detected level through mesophilic digestion tank except for Campylobacter. However, it could be reduced by 98.7% through a sterilization tank. Bacillus was detected at 8.00 and 7.81 log10 CFU/g dry matter in anaerobic digestates, and it was also resistant to sterilization tank. Bacillus spp. is considered to be the safe bacteria that hold remarkable abilities for promoting plant growth. The results showed that treatment at biogas plants is effective to reduce pathogenic bacteria in dairy manure, and sterilization could further reduce the sanitary risks of pathogenic bacteria relating to anaerobic digestate application. Anaerobic digestates could also be utilized as bio‐fertilizer as the high load of plant growth promoting bacteria.  相似文献   

14.
为研究调控饲料对奶牛产奶量和乳成分的影响,试验选择10头年龄、胎次、泌乳天数、产奶量相近的泌乳牛,按照配对试验设计分为2组,一组为对照组(饲喂基础日粮),另一组为试验组(饲喂添加调控饲料的基础日粮)。结果表明,试验组每头奶牛日均增奶量比对照组多1.366kg(P<0.05),乳蛋白、乳脂率、乳糖、乳中干物质含量相比差异不显著。通过试验前后对比可知,调控饲料显著提高了奶牛的产奶量。  相似文献   

15.

Two experiments were conducted to investigate the effects of addition of walnut shell biochar (WSB) and chicken manure biochar (CMB) to dairy ewes’ diet. In in vitro experiment, the effects of different levels of WSB and CMB (0.5, 1, and 1.5% diet dry matter (DM)) on rumen fermentation characteristics were assessed in a completely randomized design with seven treatments and three replicates. Treatments were as follows: basal diet without biochar (control), basal diet with 0.5, 1, and 1.5% WSB, and basal diet with 0.5, 1, and 1.5% CMB. Addition of 1% WSB and 1.5% CMB to the diet linearly decreased methane production and ammonia-N concentrations and increased pH compared to control (P?<?0.001). Inclusion of WSB and CMB to the diet did not change volume of gas production and total volatile fatty acids (VFA) and proportion of acetate, propionate, and butyrate. In the second experiment, six milking Kermanian ewes were used in a replicated Latin square design with three treatments and three 21-day periods to evaluate the effects of 1% WSB and 1.5% CMB (based on results obtained from in vitro trial) on intake, digestibility, and milk yield and composition. Dietary inclusion of 1% WSB and 1.5% CMB resulted in more milk yield (P?<?0.01), milk protein (P?<?0.05), and solids not fat (SNF) (P?<?0.001). Blood glucose and total protein increased (P?<?0.01) in ewes fed 1% WSB and 1.5% CMB in comparison to ewes fed control diet. Apparent digestibility coefficients of DM (P?<?0.01) and OM (P?<?0.10) were increased with inclusion of 1% WSB and 1.5% CMB in diet. Neutral detergent fiber (NDF) digestibility was also increased in WSB-fed ewes (P?<?0.01). The lack of negative effects of 1% WSB and 1.5% CMB coupled with the observed reduction in methane emission and ammonia concentration and also improvement in milk production suggested that biochars can be beneficially incorporated in dairy ewes’ ration as a low-cost feed additive.

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16.
To investigate effects of Aspergillus oryzae culture (AOC) and 2‐hydroxy‐4‐(methylthio) butanoic acid (HMB) on milk performance and rumen fermentation of dairy cows. Sixty‐four multiparous Chinese Holstein cows were randomly allocated into four experimental diets: (i) Control diet; (ii) AOC diet: 5 g AOC/day per head; (iii) HMB diet: 25 g HMB/day; and (iv) AH diet: 5 g AOC plus 25 g HMB/day. Added HMB tended to increase the yield of milk protein (P = 0.06) and 3.5% fat‐corrected milk (P = 0.08) and milk fat content (P = 0.09). Milk fat yield (P = 0.03) and the contents of milk protein (P = 0.05) were increased by adding HMB. The cows fed on AOC diet had a tendency for higher body weight (BW) gain (P = 0.08). Addition of AOC, HMB and AH increased content of microbial protein (MCP) and total volatile fatty acids (VFA) (P < 0.01) in rumen fluid. Populations of rumen fungi, Fibrobacter succinogenes and Ruminococcus flavefaciens relative to total bacterial 16S rDNA (P ≤ 0.03) and activity of carboxymethylcellulase (CMCase) (P < 0.01) were increased with added AOC or HMB. It is inferred that added AOC or HMB can increase the contents of MCP and total VFA potentially by stimulating rumen microbe populations and CMCase activity.  相似文献   

17.
The production and partial characterization of bacteriocin‐like substances (BLSs) produced by bacteria isolated from cow manure compost were investigated. Eight BLS producers, which exhibited inhibitory activity against pathogenic bacteria, were isolated from cow manure compost at different stages of the composting process. The pile temperature ranged from 9.1°C to 73.2°C. The BLSs showed thermostability, but the BLS producers were not thermostable except for the H1 producer. Thermophilic Bacillus licheniformis H1 was further characterized. The culture supernatant of B. licheniformis H1 exhibited antagonistic activity against various species of Gram‐positive bacteria such as Listeria monocytogenes ATCC19111 but not against Gram‐negative bacteria except Pseudomonas fluorescens ATCC11251. Inactivation of bacteriocin‐like activity by α‐chymotrypsin, trypsin, and papain was highly significant (P < 0.001). The BLS was found to be stable under a pH range from 3 to 9 and at temperatures up to 75°C for 60 min, but it lost activity after being autoclaved at 121°C for 15 min. The optimum production of BLS by B. licheniformis H1 was obtained at a temperature of 55°C. Sodium dodecyl sulfate – polyacrylamide electrophoresis analysis of concentrated partially purified supernatants collected after resting the bacterial cells at 55°C revealed a bacteriocin‐like protein with a molecular mass of approximately 3.5 kDa. This study is the first report of a BLS from thermophilic B. licheniformis with an animal compost origin.  相似文献   

18.
试验为研究日粮中添加菌糠对荷斯坦奶牛产奶量、乳品质、血液生化指标及抗氧化功能的影响,根据单因素随机设计,将健康、体重接近的90头荷斯坦奶牛随机分为3个处理组,每组30头.对照组奶牛饲喂基础日粮;试验1组饲喂5％的菌糠;试验2组饲喂10％的菌糠.预试期7d,正式试验期30 d.结果 表明:与对照组相比,菌糠组的乳品质指标...  相似文献   

19.
OBJECTIVE: To determine whether antimicrobial resistance patterns of major mastitis pathogens isolated from milk samples from dairy cows have changed over time. DESIGN: Retrospective study. SAMPLE POPULATION: 8905 bacterial isolates obtained from milk samples submitted to the Wisconsin Veterinary Diagnostic Laboratory between January 1994 and June 2001. PROCEDURE: Antimicrobial susceptibility was determined by means of the Kirby-Bauer disk diffusion method. Logistic regression was used to determine whether percentages of isolates resistant to various antimicrobials changed over time. RESULTS: For the gram-positive mastitis pathogens, percentages of isolates resistant to various flactam antimicrobials did not increase over the course of the study. Percentage of Staphylococcus aureus isolates resistant to penicillin decreased from 49 to 30%; percentage of Streptococcus isolates resistant to penicillin decreased from 6 to 1%. Percentage of isolates resistant to erythromycin increased for S aureus, Escherichia coli, Enterobacter spp, Enterococcus spp, and Pasteurella spp. Percentage of isolates resistant to lincomycin increased for S aureus and Staphylococcus spp. Percentage of coagulase-negative Staphylococcus isolates resistant to pirlimycin increased from 6 to 19%. For several pathogens, percentages of isolates resistant to sulfisoxazole and to trimethoprim-sulfamethoxazole decreased. No pathogens had a significant increase in the percentage of isolates resistant to novobiocin-penicillin. CONCLUSIONS AND CLINICAL RELEVANCE: Results did not indicate a trend toward increased antimicrobial resistance among mastitis pathogens isolated from milk samples from dairy cows between 1994 and 2001. Reduced resistance to flactam antimicrobials was identified for several gram-positive mastitis pathogens.  相似文献   

20.
The aim of this study was to identify methicillin‐resistant Staphylococcus aureus (MRSA) strains gathered from 2002 to 2006 from milk samples in Aydin region in Turkey. Among 93 S. aureus strains isolated from bovine milk with mastitis, 16 were resistant to methicillin. Methicillin‐resistant S. aureus strains were studied further for their staphylococcal cassette chromosome mec (SCCmec) types, pulsotypes, spa and MLST types, antimicrobial susceptibilities, mechanisms of resistance and presence of Panton–Valentine leucocidin (PVL) toxin gene. The MRSA strains were multi‐drug resistant. The susceptibility rates to antimicrobials tested were 0%, 0%, 0%, 0%, 6.25%, 16.25% and 56.25% for erythromycin, clindamycin, chloramphenicol, gentamicin, tetracyclin, ciprofloxacin and vancomycin, respectively. All tetracycline and gentamicin resistant strains carried tet(M) and aac(6)‐aph(2) gene, respectively. Among macrolide‐resistant isolates, nine had erm(A), and seven had both erm(A) and erm(B) genes. The molecular characterization by pulsed‐field gel electrophoresis showed presence of three pulsotypes with their variants. The pulsotype B strains were type IV with SCCmec typing, and representative of pulsotype B was t190 by spa typing and ST8 by MLST typing. The strains with pulsotype A and C were SCCmec III, and representative of these pulsotypes was t030 by spa typing. The MLST type of pulsotype A was ST239 and pulsotype C was one allele variant of ST239. None of the isolates harboured the PVL gene. Presence of hospital‐related MRSA strains may indicate transmission of these strains between human and animals. In case of clonal spread beside the infected animals’ treatment of MRSA carrier, farm workers should also be considered. Hygienic measures and rational antibiotic use may avoid resistance selection, clonal dissemination of resistant strains and decrease losses because of mastitis in dairy herds.  相似文献   

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