This study was conducted in the laboratory of the Ministry of Science and Technology to estimate the immunological characteristics (IgG, IgA, and IgM) and microbial content in bovine colostrum samples on the first, third, and fifth day of birth, and the effect of pasteurization treatments {pasteurization at 63° C / 30 minutes (LTLT) and pasteurization, at 72° C. / 15 second (HTST)}. Also, to determine the antibacterial activity of colostrum against pathogenic bacteria, including Staphylococcus aureus, Escherichia coli, Salmonella typhi, and Klebsiella oxytoca. The results showed that the HTST pasteurization was the most effective in colostrum samples. The results also showed that the immune globulins in colostrum were high on the first day of birth, then gradually decreased with the increase in the period from birth, and the concentration of IgG immune-globulins was highest in bovine colostrum, followed by IgM and then IgA, which reached 475.24, 185.70 and 162.00 ng ml-1 respectively. Also, the pasteurization treatments led to a significant decrease in the concentration of immune globulins compared with the control treatment (un paseurization). As for microbial content in colostrum, the results showed that the total number of bacteria and the number of coliform bacteria were low on the first day of birth and then increased on the third and fifth day of birth, while the average number of lactic acid bacteria was 2.12, 2.23, and 2.04 log CFU ml-1 respectively, and the pasteurization treatments led to a significant decrease in the microbial content in all samples, the results also showed that the colostrum samples were free of S. aureus, E. coli, and S. typhi bacteria. Regarding testing the antibacterial efficacy of colostrum against pathogenic bacterial isolates, the results showed that the highest inhibition of colostrum was on the first day of birth against S. aureus bacteria at a zone diameter of inhibition of 14 mm, followed by E. coli, then S. typhi and K. oxytoca.