Bacteriologic detection of Mycobacterium avium subspecies paratuberculosis (Mptb) was used to confirm the shedding patterns, infection status and final disease profile of cattle, sheep, goats and rabbits in 3 infection experiments. Cattle, sheep and goats were orally dosed (4 doses at weekly intervals) with up to 2x10¹⁰ cfu of a wild-type bovine Mptb isolate or with 15-20g of bovine intestinal mucosal tissue from a naturally Johne's Disease (JD) infected cow. Faecal culture was performed pre-challenge and for 4years post-challenge. Similarly a further group of cattle, sheep and goats were orally dosed with up to 2x10¹⁰ cfu of a wild-type ovine Mptb isolate or with 15-20g of ovine intestinal mucosal tissue from a naturally JD infected sheep. Faecal culture was carried out pre-challenge and for 31 months post-challenge. Finally adult and juvenile rabbits were given oral infective doses of 10⁸ cfu weekly on 3 occasions with faecal and autopsy tissue culture being used to monitor disease progression for up to 2 years. The BACTEC system of radiometric culture was used together with conventional culture for the recovery of Mptb from faecal specimens and post mortem tissues. The Growth Index was determined weekly using the BACTEC 460 and samples taken from vials initially with a GI>100 and transferred to 4 varieties of Herrolds egg yolk agar along with modified Middlebrooks 7H10 slopes. Ziehl-Neelson stained smears, Mycobactin J dependency and PCR were used as confirmatory tests. Constant, intermittent and non-shedders were detected and both high and low Mptb colony numbers were observed. Mptb was cultured and confirmed from a variety of post mortem tissues from animals manifesting different stages of JD infection. Radiometric bacteriologic culture increased the recovery of bacterial colonies for both the bovine and ovine strains of Mptb.