📖 Calf diarrhoea is one of the most important causes of calf mortality in pre-weaned calves. Early days of calf life are very important, when morbidity and mortality are the greatest. In young calves mortality varies from 8.7 to 64 per cent throughout the world. There are many diseases that can affect the calf during its infancy however; calf diarrhoea is the most important disease problem in dairy calves that causes more economic losses to the calf producer than any other problem. Calf diarrhoea causes 75 per cent of mortality of dairy calves having age of less than three weeks. The prevalence of E. coli was found more in diarrhoeic cattle (38%) and buffalo (48%) calves as compared to healthy cattle (14%) and buffalo (16%) calves. While, E. coli having F5 (K99) antigen was observed more in buffalo calves (45.83%) as compared to cattle calves (31.6%). Therefore, this study showed that prevalence of E. coli in both young diarrhoeic cattle and buffalo calves was high as compared to healthy calves. However, it is necessary to identify the risk factors associated with bacteria causing diarrhoea and that may be helpful for prevention and control of calf diarrhoea