Background: Nowadays, colostrum has been known as a considerable and valuable by-product of large-scale dairy production in the world. The main objective of this study was to evaluate the effects of pasteurization, spray-drying and freeze-drying methods on bacterial loads and Immunoglobulin G (IgG) level of bovine colostrums. Methods: Colostrum samples were collected from the first milking postpartum of Iranian Holstein dairy cattle farms. The samples were treated by pasteurization (60 ° C for 30 min and 55 ° C for 60 min), spray-drying and freeze-drying methods. Standard Plate Counts (SPC), Escherichia coli count, and Total Coliform Count (TCC) were analyzed at days 1, 10, 20, and 30 of storage. Also, IgG level were assessed at the end of 30-day storage. Statistical analysis was performed using SPSS 17. 0 (Chicago, IL, USA) software. Results: Although all four treatments showed direct impact on reduction of SPC, TCC, and E. coli count in colostrum stored at 1, 10, 20, and 30 days, but the spray-drying and freeze-drying methods were significantly (p<0. 05) more effective to reduce microbial loads. The mean IgG levels of the samples were 60. 35 mg/ml for untreated samples (control); 30. 65± 6. 95 mg/ml for spray-dried treatment; 36. 97± 6. 79 mg/ml for freeze-dried treatment; 28. 12± 6. 53 mg/ml for heated treatment at 60 ° C/30 min; and 34. 97± 9. 80 mg/ml for heated treatment at 55 ° C/60 min. All four treatments resulted in significant (p<0. 05) reduction of the IgG levels. Conclusion: Considering the obtained results, it seems that freeze-drying and spraydrying methods could be more effective than pasteurization ones to enhance quality and shelf life of bovine colostrum for a long time.