To meet the demand of iron, an essential factor for growth, mycobacteria synthesize cell associated compounds called mycobactins to grow in iron restricted conditions. Mycobacterium avium subsp paratuberculosis is unable to synthesize required amount of mycobactin and require exogenous mycobactin. The mycobactins were extracted from various mycobacterial species can be used as a growth promoter of Mycobacterium avium subsp paratuberculosis. This book provide detail review on paratuberculosis and mycobactin production.