Cryptosridiosis is a life threatening illness of neonatal calves, leading to mal-absorption and diarrhea. The present study was carried out on 25 Holstein dairy calves, 3 to 15 days old in El-Eman farm, Ismailia Governorate, Egypt. Animals were assigned into two groups; G1: included 20 calves suffered from watery to mucoid diarrhea and G2: included 5 calves were proved to be clinically healthy and used as a control one. The diseased calves were treated by oral administration of Halofuginone at a dose rate of 100 μg per kg once daily for 7 successive days. A total number of 90 blood and fecal samples were obtained from all animals during the study; 40 blood samples from diseased calf (at the onset of the appearance of the symptoms and on the 8th day of the treatment), 40 fecal samples at the same pattern from the same animals and 10 samples (blood and feces) were collected from the control one. Forty-five blood samples were analyzed for serum enzyme activities of ALT, GGT and LDH and for serum levels of urea, creatinine, total protein, albumin, globulin, IgA, TC, TGs, HDL-C and LDL-C. The later, forty-five fecal samples were examined to detect Cryptosporidium infection utilizing ICT, microscopical and molecular identification based on 18S rRNA Gene. Clinically infected dairy calves showed clinical signs of profuse watery diarrhea with yellowish colored feces (40%) and other calves showed mucoid diarrhea
(60%) which persist for 7 days resulting in dehydration, weakness and loss of body weight. The study revealed a significant increase in levels of ALT, GGT, LDH and urea with a highly significant reduction in concentration of IgA in the diseased calves. Meanwhile, a non-significant change in levels of total protein, albumin and globulin were reported among all groups. Lipid profile of the diseased calves revealed a significant increase in both levels of T.C and LDL-C with a highly significant reduction in the level of T.Gs in the diseased calves. Meanwhile, HDL-C level showed a non-significant change in all groups.