Diarrhea in calves under 30 days of age is one of the most common syndromes. In order to present a useful and convenient method for reduction of calf diarrhea, thirty newborn Holstein calves, with normal parturition, were divided randomly into three equal groups (T1, T2 and Control (C)). Calves weighing 31-40 kg and more than 40 kg at birth were respectively offered 2 and 2.5 kg of vaccinated cow’s colostrum immediately after birth and the same amounts 4-6 hours later. All calves were fed milk twice daily. Both groups T1 and T2, were fed once daily, 0.8-1 kg of respectively thawed and natural fermented colostrums diluted with 1-1.2 kg cow milk from 2^nd to 30^th day of their life. Ten calves of Group C were fed only 1.8-2.5 kg warm milk in each meal everyday. Calves were weighed at 0, 10th, 20th and 30th day after birth. Incidence and severity of diarrhea were recorded based on current landmarks. Totally 143 cases of diarrhea recorded. The cumulative incidence rate of diarrhea was significantly (P<0.05) lower in group T1 (27.9%) and group T2 (29.35%) when compared with group C (42.8%). Little differences in average daily weight gain were recorded and weight gain for 0-30 days, were similar for two treatments. The calves given colostrum daily were less affected by squirt. Not only incidence but also severity of diarrhea in groups T1 and T2 was significantly less than in group C (P<0.05). Although the incidence of scours in group T1 was less than group T2, this difference was not significant (p>0.05).

Key words: Calves; Diarrhea; Fermented colostrums; Frozen colostrums; Vaccinated cow