Livestock is an integral part of the agricultural production system in some countries and plays an important role in national economy as well as in socio-economic development of millions of rural household. Ethiopia basically constitutes an agrarian society; the socio-economic activities of about 85% of the population are based on farming and animal husbandry. Livestock plays a critical role for the majority of the Ethiopian population. Domestic animals are mainly used as drought animals, source of milk, meat, hide and skin and as pack animals. Apart from this they also serve as a means of risk diversion and accumulation of wealth among the rural community .
Dairy production is a critical issue in Ethiopian livestock -based society where livestock and its products are important sources of food and income. The substantial demand-supply variance in milk and milk products for the major urban centers in Ethiopia is a great opportunity for the development and flourishing of peri-urban dairy farms. Peri-urban and urban dairies are intensive production systems, which keep high-grade cows and have improved management practices. This is usually associated with increased susceptibility to disease, poor survival rate and poor reproductive. The country has large potential for dairy development mainly due to large livestock population, the favorable climate for improved high yield breed, and relatively diseases-free environment 
Newly born calves are important source of animal production for either meat or breeding worldwide. Calves are important assets for replacement of cows for the future dairy and beef herd sustainability. It is needed to rear healthy calves. In the calf, losses have been as high as 50% of calf crop because of poor management and low adaptation of exotic dairy breed to tropical environment . Calf hood diseases have, therefore, a significant financial impact on dairies resulting from treatment costs, genetic loss, and impaired future performance . Diarrhea is a leading cause of economic losses to most countries . Its etiology is complex involving management, environmental, nutritional, physiological variations and variety of pathogens including bacteria, viruses, protozoa and intestinal parasites are described as important agents causing diarrhea (either separately or in combination) in calf .
Calf diarrhea caused by bacterial infection has a bad effect on the dairy industry all over the world when calves are reared intensively. It involves significant economic loss for labor and capital, calf mortality, loss in calf value and veterinary costs [7; 8]. Among these bacteria E.coli and salmonella are believed to be the major microbial causes of calf diarrhea [9; 10]. According to Lorenz , calf morbidity and mortality by diarrhea have short-term and long-term detrimental effects on performance of a dairy farm. They impair both growth rate and replacement capacity of the herd. The economic losses occur not only from mortality but also from treatment costs and time spent on care as well as subsequent chronic ill, thrift and impaired growth performance . In order to increase the productivity per livestock unit without increasing livestock numbers and to devise preventive measures as well as to reduce losses during the initial months of life it is important to identify the etiological agents involved in calf diarrhea [13; 14].
Current treatment regimens for the treatment of neonatal calf diarrhea center on antimicrobial therapy and fluid therapy. Antimicrobial agents are considered popular to fight diarrhea in calves. Nevertheless, their wide spectrum of activity, the emergence of microbial tolerance of different antimicrobial agents has become a well- known phenomenon, which represents a major concern. Resistance to antimicrobial agents was frequently occurred in Salmonella species and E. coli particularly in pre-weaned dairy calves . Antibiotic resistance to bacteria is a serious and growing phenomenon and has emerged as one of the preeminent public Health concerns of this century. The choice of which antibiotic is likely to be most effective requires knowledge of potential resistance. The practice of under dosing, over dosing as well as indiscriminate usage of drugs are not uncommon in Ethiopia, As a result, bacterial strains are being developed which are multidrug resistant and new types of antibiotics are required for the prevention and control of diseases.
Discontinuation or incomplete course of treatment and continuous indiscriminate uses of antibacterial drugs against diarrheal infection of man and animal creates a potential health risk to animals and humans in terms of drug residues and the development of resistant bacterial strains. Although routine laboratory isolation and drug sensitivity testing are expensive and impractical, the periodical check of the pattern of the drug sensitivity of organisms is more important. It is, therefore, important that sensitivity of different bacteria isolated from diarrheic calves needs to be studied from time to time in order to formulate appropriate therapeutic measures . In order to increase the productivity per livestock unit without increasing livestock numbers, it is important to identify the etiological and predisposing factors involved in calf diarrhea in order to devise preventive measures and reduce losses during the initial months of life [18; 13].
Dairy farming is a growing livestock production system in Ethiopia. It is primary source of income for urban and peri-urban poor communities. Because of better availability of milk market, most of the dairy farms are concentrated in urban and peri-urban areas of the country. They also increase the use of exotic dairy cattle and their crosses in order to enhance milk production. In Ethiopia in general calf morbidity and mortality due to calf diarrhea is a challenging problem for dairy producers. However, there is no coordinated surveillance and assessment for prevalence and risk factors inducing this problem and there is also little information available regarding to this problem. Accordingly, the objectives of this research were to isolate and identify of salmonella and E. coli infection in diarrheic calves, to assess risk factors for occurrence of calf diarrhea and to examine antimicrobial susceptibility of isolated bacteria’s in and around Sebeta town.