[Objective] To clone and express the DnaJ gene in Mycoplasma ovipneumoniae, and to assess the immunogenicity of its expression product. [Method] Using genomic DNA extracted from Mycoplasma ovipneumoniae NM03-MO strain isolated from Inner Mongolia as template, DnaJ gene was cloned. The DnaJ protein sequence was analyzed and its three-dimensional structure was predicted. A pColdⅠ-DnaJ prokaryotic expression vector was constructed with the cloned DnaJ gene fragment being connected to pColdⅠ vector to express the recombinant DnaJ protein. The obtained DnaJ protein was purified, and its binding activity to Mycoplasma antibody positive serum was evaluated by Western blot. [Result] The NM03-MO strain′s DnaJ protein had the highest homology to Mycoplasma ovipneumoniae, while there were minor differences in the three-dimensional structure. The recombinant DnaJ protein displayed high binding activity to Mycoplasma ovipneumoniae positive serum, indicating that it was a immunogenic protein. [Conclusion] For the first time, the DnaJ protein of Mycoplasma ovipneumoniae was successfully cloned and expressed and had good immunogenicity. This research lays the groundwork for the further molecular pathogenesis research and the development of novel vaccines.

[Objective] To determine the process parameters of production technology of a vaginal probiotic preparation using lactic acid bacteria of horse origin. [Method] A Lactobacillus gasseri strain isolated from Mongolian horse vagina, was used as a starter to product the probiotic preparation. Fermentation technology and response surface method were employed to optimize the strain′s fermentation medium and process parameters as well as the probiotic preparation′s formulation and process parameters. [Result] Lactose and soybean peptone had significant impacts on growth performance of the bacterial powder. When the initial pH value of the fermentation broth was set to 6.6, the temperature was set to 40 ℃, and the inoculation amount was set to 6%, the fermentation performance of the bacterial powder was largely influenced. Using pharmaceutical preparation technology and response surface method, the probiotic preparation′s formulation and process parameters were then adjusted. When the mixing ratio of bacterial powder to starch, micro-powder silica gel, and micro-crystalline cellulose was 167.05∶1.61∶1 and the rotating speed of multi-functional medicine machine was 20 r/min at 60 ° angle, the number of live bacteria in the obtained probiotic preparation was higher. [Conclusion] The critical process parameters for production of vaginal probiotic preparation with horse origined Lactobacillus gasseri were determined, providing a foundation for further explorations on the use of probiotic preparations made by live bacteria to prevent and treat horse vaginal infection.

[Objective] To investigate the effects of different levels of grape seed pomace （GSP） replacing partial corn and cottonseed meal in concentrate supplements on in vitro rumen gas production, in vitro nutrients digestibility, fermentation parameters, and growth performance of Simmental cattle. [Method] Using the rumen simulation technique, corn and cottonseed meal in concentrate supplements were partially replaced by GSP at proportions of 4%, 8%, 12% and 16%, respectively. The in vitro gas production, fermentation parameters, in vitro nutrients digestibility of each groups were measured, and the growth performance of the cattle fed with diets in which corn and cottonseed meal were partially replaced by different levels of GSP were evaluated. [Result] The cumulative gas production increased as the in vitro fermentation period extended. The 12% GSP group produced the most gas, and there was no significant （P>0.05） difference in total gas production across the different groups at 72 h of fermentation. There were no significant （P>0.05) differences in pH value, NH₃-N concentration, or bacterial protein content in the artificial rumen fluid between the different groups after gas production. The concentrations of volatile fatty acids increased significantly （P<0.05) in the experimental groups. The digestibility of dry matter was the lowest in the 16% GSP group. The digestibility of crude protein in the control group was significantly （P<0.05) higher than that in the experimental groups. The digestibility of neutral detergent fiber in the control group and the 4% GSP group was significantly （P<0.05) higher than that in the other three groups. The digestibility of acid detergent fiber in the control group and the 12% GSP group was significantly （P<0.05) higher than that in the other three groups. The average daily gain of the cattle in the 4% and the 8% GSP groups was 170 g/d and 140 g/d higher than that of the control group, respectively. [Conclusion] Replacement of partial corn and cottonseed meal in concentrate supplements with GSP improved the concentrations of volatile fatty acids in artificial rumen fluid. Replacing proportions of 4% or 8% of GSP increased the daily gain and boosted the rumen fermentation of beef cattle, which was conducive to improve the growth performance.

[Objective] To assess the effects of varied harvest periods on agronomic traits and biological yields of two maize varieties, screen the maize varieties suitable for preparing silage in Liangcheng County, Ulanqab City,Inner Mongolia, and determine the best harvest period. [Method] A whole plant silage maize variety Jidong 81 and a grain maize variety Ganyou 702 were used as experimental materials. A total of 11 harvest dates during 5^th September and 5^th October in the year 2019 were set. The plant heights as well as fresh matter yields, dry matter contents and dry matter yields in different parts of the tested maize were monitored and statistically compared. [Result] The plant heights of the two maize varieties increased at first and then stabilized with the extension of the harvest periods. The maximum plant heights were observed on 17^th September in both Jidong 81 and Ganyou 702, which were 3.51 m and 2.94 m, respectively; the average plant height of Jidong 81 was significantly （P<0.05） higher than that of Ganyou 702 during the experimental period. The fresh matter yields of stems and leaves, stalks, ears and whole plant of the two maize varieties increased first and then decreased, their dry matter contents showed an gradually increasing trend, and their dry matter yields increased at first and then stabilized. There was no significant （P>0.05） difference in the whole plant average fresh matter yield between the two maize varieties. Jidong 81 had significantly （P<0.05） lower whole plant average dry matter content and whole plant average dry matter yield in comparison to Ganyou 702. [Conclusion] The best harvest period for the whole plant silage maize variety Jidong 81 was from 23^th to 26^th September, and that of the grain maize variety Ganyou 702 was from 17^th to 20^th September. Under the same planting conditions, Jidong 81 was more suitable to be promoted in this area.

The impacts of maternal nutrition on fetal gene expression has gradually become the focus in perinatal life nutrition research. The most important window of developmental plasticity is gestational period. Epigenetics may be implicated in the modification of metabolic genes associated with fetal development by methyl donors. In animal experiments, insufficient or excessive maternal nutrition has been proven to impede the fetal growth. By consulting the scientific reports abroad and in China, this paper discussed the maternal and fetal nutrition needs during gestational period, the roles of hormones in homeostasis regulation, and the importance of energy demands during gestational period on pregnancy health in herbivorous livestock. This paper also summarized the research progress of herbivores nutrition during gestational period in epigenetics, and discussed the application of epigenetic technologies in herbivorous livestock breeding, in hoping to provide references for formulating the best nutrition strategy for herbivores during gestational period, improving embryo quality, and breeding high-quality offspring.

Bone is the basic framework of the body structure. The dynamic homeostasis between bone formation and bone resorption determines the bone health. Calcium and phosphorus are important mineral elements involved in animal bone growth and development, and their absorption and regulation by the body directly affect the bone metabolism. Changes in serum calcium and phosphorus levels alter the body′s secretion of relevant regulatory hormones that affect bone development. Therefore, calcium and phosphorus metabolism is closely related to bone health. Based on the researches on calcium and phosphorus metabolism as well as bone metabolism abroad and in China, this paper reviews the absorption and metabolism of calcium and phosphorus, their contents and proportions, and the regulatory mechanism of calcium and phosphorus metabolism related adjusting hormones on bone development, in hoping to provide references for further studies on the regulation of calcium and phosphorus metabolism and bone in animals.

[Objective] To assess the purification effect of spatial electric field on greenhouse gas and its impact on temperature and humidity in the livestock house in winter and spring. [Method] The spatial electric field purification equipment as well as temperature and humidity monitors were installed in the livestock house. Three air extraction points were set inside and outside livestock house, respectively, and four heights including 0 m, 0.5 m, 1.0 m and 1.5 m were set for each air extraction point. The changes of greenhouse gas concentrations as well as temperature and humidity during winter and spring were systematically monitored. [Result] Spatial electric field significantly （P<0.05 or P<0.000 1） reduced the concentrations of CH₄, NH₃ and CO₂ inside the livestock house in winter and spring by 39.8%, 26.3% and 24.0%, respectively. Spatial electric field significantly （P<0.05） decreased the ambient humidity inside the livestock house from 20：00 to 8：00 and from 12：00 to 15：00 in winter by 4.5% and 15.3%, respectively. In spring, the ambient humidity inside the livestock house was significantly （P<0.05） decreased by 31.9% from 9：00 to 17：00. [Conclusion] The spatial electric field can effectively reduce the concentrations of CH₄, NH₃ and CO₂ and significantly decrease the indoor humidity of different time duration in the livestock house in winter and spring.

In pastoral areas of North China, the cold season has a negative impact on the mutton sheep industry. Grazing ewes need energy to cope with the heat loss during the cold season, resulting in a drop in feed reward, which has become a main factor driving up the rearing cost of grazing and supplementary feeding production mode in the cold season. Animal husbandry′s long-term profitability depends on low-cost production. This paper investigated the main problems of grazing production of mutton sheep in the cold season in North China, as well as the importance of low-cost production mode. Based on the concept of circular economy, this paper proposed a low-cost rearing mode of mutton sheep in the cold season in pastoral areas of North China, expounding the connotation of the technical mode from three perspectives: preparing low-cost total mixed ration, converting production mode, and building welfare and low-cost warm shed. Furthermore, the environmental quality index in the warm shed, the rearing effect, and the cost comparison were used to evaluate the practical application effect of this technical mode. This paper also rendered some thoughts on the industrial application of low-cost rearing mode of mutton sheep in the cold season in pastoral areas of North China, in hoping to provide references for accelerating the transformation of mutton sheep production mode in the cold season and improving the rearing economic benefits in pastoral areas of North China.

[Objective] To assess the effects of various nutrient treatments on population characteristics and grass yields of Stipa grandis grassland. [Method] In Tumuji Town, Jalaid Banner, Hinggan League, Inner Mongolia, the impacts of organic fertilizer application, chemical fertilizer application, grazing, and control （without management methods） on grassland population characteristics and grass yields were analyzed with random block design in the year of 2021. Single component analysis and multiple comparison were used to examine the variations in grassland population characteristics and grass yields across the four treatments. [Result] Grassland population characteristics and grass yields were affected differently by various treatments. Compared with the control, the treatments of organic fertilizer, chemical fertilizer, and grazing all raised the importance value of Achnatherum sibiricum, with chemical fertilizer treatment increased significantly （P<0.05）, while the importance value of Stipa grandis and Arundinella hirta dropped. Organic fertilizer treatment enhanced grass height in comparison to the control, whereas the treatments of chemical fertilizer and grazing lowered grass height. Chemical fertilizer treatment increased grass coverage significantly （P<0.05） compared to the control, but the treatments of organic fertilizer and grazing reduced grass coverage. The treatments of organic fertilizer and chemical fertilizer increased grass yields compared to the control, with chemical fertilizer treatment increased extremely significantly （P<0.01）, but grazing treatment decreased fresh grass yields. [Conclusion] Organic fertilizer treatment improved the importance value , grass height, and grass yields of Achnatherum sibiricum, and chemical fertilizer treatment improved the importance value , grass coverage, and grass yields of Achnatherum sibiricum.

[Objective] To identify the key agronomic traits that greatly influence the yield of Sorghum-Sudan hybrid grass, unlock its high-yield potential, and lay the foundation for variety breeding, promotion, and application. [Method] The agronomic traits of 12 materials of Sorghum-Sudan hybrid grass were measured. The correlation, principal component, and path analysis between main agronomic traits and dry weight per plant were performed using a random block test. [Result] The coefficient of variation of the different agronomic traits ranged from 11.61% to 54.67%, showing that the principal agronomic traits varied widely across the materials evaluated. The correlation between the evaluated agronomic traits and dry weight per plant were plant height > stem diameter > number of leaves > leaf length > leaf width. The strongest correlation coefficient（0.746） was found between dry weight per plant and plant height, whereas the least （0.349） was found between dry weight per plant and leaf width. Principal component analysis yielded three main traits: plant height, tillering, and leaf width. In principal component analysis, the contribution rates of the first three were 45.855%, 12.924%, and 11.594%, respectively, with a cumulative contribution rate of 70.373%. In principle component 1, the eigenvectors of the evaluated agronomic traits were all positive, and the load of dry weight per plant, plant height, stem diameter, number of leaves, and leaf length was higher. This means that high yield of Sorghum-Sudan hybrid grass was achieved when the plant was tall, the main stem was thick, the number of leaves was large, and the plant leaves were long. In path analysis, the direct effect on plant yield was plant height （0.444） > stem diameter （0.258） > number of leaves （0.201） > leaf width （0.136）. [Conclusion] Plant height and stem diameter are essential agronomic traits that have direct impacts on a single plant′s yield of Sorghum-Sudan hybrid grass.

[Objective] To assess the effects of various ecological restoration measures on vegetation community characteristics and species diversity in Mu Us desertified grassland. [Method] To restore the desertified grassland in Sulide Sumu, Uxin Banner, Ordos City, Inner Mongolia, using enclosure as control （Ⅳ）, the measures of fertilization （Ⅰ）, reseeding (Ⅱ), algae spraying （Ⅲ）, algae reseeding and seed dressing （Ⅴ）, and fertilization+reseeding （Ⅵ） were utilized. The responses to these ecological restoration strategies were assessed by monitoring the vegetation community characteristics and calculating the species diversity indexes. [Result] The average height of vegetation community in the treatment areas of fertilization （Ⅰ）, reseeding （Ⅱ）, algae spraying （Ⅲ）, algae reseeding and seed dressing （Ⅴ）, and fertilization+reseeding （Ⅵ） was significantly （P<0.05） higher than that in the control area （Ⅳ）. The vegetation community coverage, density and above ground biomass in the treatment area of algae reseeding and seed dressing （Ⅴ） were significantly （P<0.05） higher than those in the other five treatment areas. The treatment area of fertilization （Ⅰ） had the most plant species with a total of 20 species, while that of reseeding （Ⅱ） had the least with a total of 10 species. The Margarlef richness index and Shannon-Wiener diversity index in the treatment areas of algae spraying （Ⅲ）, fertilization （Ⅰ）, and algae reseeding and seed dressing （Ⅴ） were significantly （P<0.05） higher than those in the other treatment areas. [Conclusion] The vegetation community characteristics and species diversity in the desertified grassland were significantly affected by various restoration measures. The procedures involving nutrient input, such as algae spraying or dressing, and fertilization, had a significant short-term effect on the rapid restoration of desertified grassland. Plant species and species richness raised dramatically following restoration, and the vegetation communities became relatively complex.

[Objective] To analyze the current state of agriculture and animal husbandry integrated management under the grassland ecological protection subsidy and incentive policy. [Method] The households engaging in integrated management of agriculture and animal husbandry in X village, Bairin Right Banner, Inner Mongolia, are taken as research objects, and the data are gathered through literature review and household survey. The case analysis approach is used to analyze their fundamental features, application of policy subsidies and associated influencing factors. The benefit maximization analysis method is employed to assess the revenue and expenditure of the households engaging in integrated management of agriculture and animal husbandry. The inductive reasoning analysis approach is utilized to summarize the research findings and propose solutions to the issues arisen. [Result] Livestock are reared in confined mode for extended time, usually 4.5 months, which has become the primary cause of the increased operating costs for households engaging in integrated management of agriculture and animal husbandry. Although renting others′ pasture and forage planting base, grazing density of large- and medium-scale households is still significantly higher than the grazing density standard in this area, resulting in overgrazing. Grazing prohibition subsidies of medium- and small-scale households basically make up for the increased forage costs during the grazing prohibition period. However, the subsidy is insufficient for the large-scale households to cover the increased forage costs during the grazing restriction period, leading in grazing during the prohibition period. The main source of revenue for large- and medium-scale households is family operating income, whereas the transfer income of small-scale households dominates by the policy subsidy and is close to the entire family operating income, showing that the scale economies effect are gained at the expense of grassland ecology. Countermeasures and suggestions are proposed in light of the aforementioned issues, including revising grazing standards, learning from the ′hoof and leg theory′ experience, implementing the ′three changes reform′ system, and changing the distribution mode of grassland ecological protection subsidy and incentive funds. [Conclusion] This paper clarifies the current situation and existing problems in agriculture and animal husbandry integrated management under the grassland ecological protection subsidy and incentive policy, and provides references for the income increasing of households engaging in integrated management of agriculture and animal husbandry as well as the accurate and effective implementation of the grassland ecological protection subsidy and incentive policy.

The pig industry is not only a foundation of Yunnan Province′s agricultural and rural economy, but also a critical industry for Yunnan Province to establish a world-class green food brands. It is of great significance to build autochthonous pig brands. This paper analyzed the basic status of product brand construction of some pig breeding companies and 15 autochthonous pig breeding enterprises in Yunnan Province. In light of the issues that exist in the construction of autochthonous pig brands in Yunnan Province, such as the lack of influential regional public brands, the weakness of pertinence and systematicness of brand promotion, and the unclear product brand positioning, this paper offers some recommendations, including brand positioning differentiation, product diversification, marketing means diversification, breed improvement, and manufacturing process standardization, in hoping to provide references for the development of autochthonous pig industry and upgrade of the pork brands in Yunnan Province.

The beef cattle breeding provides foundation for the development of beef cattle industry. In Tongliao City, the beef cattle breeding started early and developed well, taking the lead of China′s beef cattle breeding industry. A complete elite breeding system has been established including breed production, supply and promotion. The origin of elite breed sources have steadily changed from foreign introduction to local breeding as the application of modern livestock breeding technology. Modern breeding technology and elite breeds have made a significant contribution to the development of the beef cattle industry. The fundamental and supporting role of the beef cattle breeding in the development of beef cattle industry has been continuously strengthened. This paper reviewed the development process of beef cattle breeding industry in Tongliao City from relying on foreign introduction to the production of frozen semen and then to the local breeding of elite breeds, analyzed the problems and weakness in beef cattle breeding industry in Tongliao City in terms of breeding foundation, joint breeding mechanism, and breeding technology innovation, and proposed some development countermeasures including the implementation of beef cattle breeding industry upgrading project, improvement of breeding technology system, acceleration of scientific and technological innovation, and development of breeding mechanisms.

Improved livestock and poultry breeds are critical to the development of animal husbandry industry. They are not only the foundation for development of regional animal husbandry industry, but also the focus of competition in science and technology of animal husbandry industry among various countries. Modern breeding technology of improved livestock and poultry breeds is composed of a series of technologies. Its employment in animal husbandry production aids in increasing the application efficiency of high-quality livestock and poultry for breeding use, speeding up the process of regional livestock and poultry breeding improvement, and improving livestock and poultry production performance. This paper introduced the application status of the main breeding technology of improved livestock and poultry breeds in China, analyzed the impacts of modern breeding technology of improved livestock and poultry breeds on feed and forage conversion efficiency as well as on selection efficiency of improved livestock and poultry breeds. In addition, this paper discussed the relationship between modern breeding technology of improved livestock and poultry breeds and input and output of livestock and poultry farm from economic perspective, in hoping to provide references for the construction of a modern breeding system for improved livestock and poultry breeds in China.

[Objective] To explore selenium level of livestock milk in Inner Mongolia. [Method] A total of 48 mixed milk representative samples that involves 188 individual animals of Bactrian camel, Mongolian horse, Saanen goat and Holstein cow, were collected from 8 banners/counties from the northeast to the west part of Inner Mongolia Autonomous Region. Selenium was determined by atomic fluorescence spectrometry, and statistical analysis and comparison were conducted. [Result] There were extremely significant regional differences on selenium content among each of the four livestock milk in Inner Mongolia: selenium in Bactrian camel milk from Alagxa Left Banner[（5.96±0.41） μg/kg] was twice higher than that of Ewenki Autonomous Banner [（2.89±0.12） μg/kg], selenium in Holstein cow milk from suburb of Hohhot City [（8.74±0.22） μg/kg] was about 3.8 times higher than that of Ewenki Autonomous Banner [（2.26±0.41） μg/kg], while, selenium in Mongolian horse milk from Zhenglan Banner[（6.65±0.57）μg/kg] was 6.5 times higher than that of Ewenki Autonomous Banner[（1.02±0.42） μg/kg]. In the west part of Inner Mongolia, selenium of goat milk from Hanggin Banner[（8.95±1.32） μg/kg] slightly higher than Wuyuan County [（6.28±0.80） μg/kg] but without significant differences （P>0.05）. Selenium in different animal milk also were significantly different. Generally, Bactrian camel, Saanen goat and Holstein cow had higher milk selenium level. Selenium level of Saanen goat milk was significantly higher than that of Mongolian horse milk （P<0.05）. Selenium data were all very much dispersed, implies that the selenium in milk not only has west to east regional differences, but also has local geographical abundance effect, may also influenced by foreign feed and forage, and salt blocks as well. [Conclusion] In Inner Mongolia, selenium level of livestock milk is generally lower, and milk selenium of northeastern part was significantly lower than that in central and western part. Selenium-rich feeding is an effective way to high quality development for the dairy livestock farming and dairy processing industry as well.

[Objective] To evaluate the meat performance, slaughter performance, and meat quality of Dumeng mutton sheep. [Method] A total of 60 Dumeng mutton sheep, half male and half female, were chosen. The live meat performance of the experimental sheep was assessed with ultrasonic backfat tester at the age of 5 months, and they were slaughtered at the age of 6 months to evaluate the parameters associated with slaughter performance, meat quality and edible safety. Furthermore, the differences in indicators of live meat performance, slaughter performance, meat quality and edible safety between ewes and rams were statistically analyzed and compared. [Result] In terms of live meat performance, the rams had significantly （P<0.05） higher psoas muscle thickness and eye muscle area than the ewes, while no significant （P>0.05） difference in backfat thickness between rams and ewes was observed. The backfat thickness and eye muscle area of the rams measured after slaughter were significantly （P<0.05） higher than those of the ewes. The carcass weight, net meat weight, and live weight before slaughter of the rams were significantly （P<0.05） higher in comparison to those of the ewes. While the rams had higher slaughter rate and carcass net meat rate than the ewes, no statistical differences （P>0.05） were found. The thigh bone weight, calf bone weight, thigh bone length, and calf bone length of the ewes were significantly （P<0.05） lower compared with those of the rams. For both rams and ewes, there were positive correlations between the four bone indexes when pairwisely compared, and the thigh bone weight and calf bone weight were more prone to be linearly correlated. The rams had significantly （P<0.05） lower intramuscular fat content than the ewes, and there was no significant （P>0.05）difference in moisture content of carcass muscle between rams and ewes. The muscular contents of lead, chromium, mercury and arsenic of the rams and the ewes were all in line with the edible safety requirements listed in China′ s national standard of Safety Qualification for Agricultural Product （GB 18406.3-2001）. The ewes had significantly （P<0.05） lower muscular contents of chromium and mercury than the rams. [Conclusion] The live meat performance and slaughter performance of Dumeng mutton rams are superior to those of the ewes, while ewes have better meat quality.

With the growing bond between humans and their pets, issues such as pet itching caused by ectoparasites infestation have gradually surfaced, drawing attention to pet health. At the same time, people should be more aware of the potential of infections being transmitted from pets to humans caused by fleas, ticks, and other insects carried pathogens. To effectively prevent and treat pet ectoparasites infestation, many researchers have developed preparations to kill pet ectoparasites. The insecticide pyriproxyfen, for example, is a type of chitin synthesis inhibitor belonging to alkoxypyridines and juvenile hormone with a unique action mechanism and a notable effect on pest management. This study summarizes current research progress on the physical and chemical properties, action mechanism, detection methods, and the effects on ectoparasites of pyriproxyfen, in hoping to provide references for future anthelmintic medication development as well as prevention and control of ectoparasites infestation.

African swine fever （ASF） is an acute and hemorrhagic infectious disease caused by the African swine fever virus （ASFV） in farmed pigs and wild boars. Pigs infected with a highly virulent ASFV strain have a near 100% mortality rate, resulting in massive economic losses for the pig industry. ASFV spreads quickly and effectively in pigs and persists in the environment, posing challenges for prevention and control of ASF. The development of ASF vaccine has been a priority for researchers. There hasn′t been a successful vaccine on the market yet. In order to give a reference for successful research and development of ASF vaccine, this paper reviewed the current research status of ASF inactivated vaccine, live attenuated vaccine, subunit vaccine, DNA vaccine, and live viral vector vaccine.

[Objective] To determine the causive agent of calf diarrhea in a family livestock farm in New Barag Right Banner of Hulun Buir City, Inner Mongolia, and to provide references for drug selection for treatment of calf diarrhea in this farm. [Method] Diseased calves′ anal swabs were obtained aseptically for bacterial culture, identification and in vitro antimicrobial sensitivity test. [Result] A bacterial strain was isolated from the anal swab samples of the diarrhea calves. The colonies were similar in morphology in the culture. The strain was identified as Providencia rettgeri by Gram′s staining, physiological and biochemical identification, and 16S rDNA sequence analysis. It was resistant to aztreonam, ceftazidime, cefotaxime, cefepime, ceftriaxone, tetracycline, chloramphenicol, and furantoin, moderately sensitive to ampicillin and gentamicin, and sensitive to cefoxitin, streptomycin, piperacillin, amikacin, ofloxacin, norfloxacin, and levofloxacin. [Conclusion] Providencia rettgeri is the causive agent of calf diarrhea in this farm. For clinical treatment, streptomycin is recommended.

[Objective] To investigate the prevalence of Staphylococcus aureus associated with mastitis and its sensitivity to the commonly used antibiotics in a dairy farm in Taizhou City. [Method] Nine milk samples were recovered from the dairy cows with mastitis. The bacterial strains were isolated with Baird-Parker agar medium, and the obtained isolates were subjected to phenotypic indentification by biochemical reactions as well as molecular comfirmation by PCR assay. Furthermore, the antimicrobial sensitivity test of the isolates were carried out. [Result] Six Staphylococcus strains were obtained and identified using the coagulase test and 16S rDNA sequencing, three of which were comfirmed as Staphylococcus aureus. According to antimicrobial sensitivity test, all three strains of Staphylococcus aureus were resistant to penicillin G, two strains were resistant to tetracycline, and two strains were intermidiate to erythromycin and oxacillin. [Conclusion] The Staphylococcus aureus isolates were mostly resistant to penicillin G and tetracycline, but susceptible to the other tested antibiotics.