Look below for the difference in the way you use the dbcc showcontig command

--DBCC SHOWCONTIG(TABLE_PROD_RES)

DBCC SHOWCONTIG scanning 'TABLE_PROD_RES' table...

Table: 'TABLE_PROD_RES' (1241211622); index ID: 1, database ID: 5

TABLE level scan performed.

- Pages Scanned................................: 748041

- Extents Scanned..............................: 93513

- Extent Switches..............................: 93526

- Avg. Pages per Extent........................: 8.0

- Scan Density [Best Count:Actual Count].......: 99.98% [93506:93527]

- Logical Scan Fragmentation ..................: 0.01%

- Extent Scan Fragmentation ...................: 10.43%

- Avg. Bytes Free per Page.....................: 351.9

- Avg. Page Density (full).....................: 95.65%

DBCC execution completed. If DBCC printed error messages, contact your system administrator.

--DBCC SHOWCONTIG(TABLE_PROD_RES) WITH FAST

DBCC SHOWCONTIG scanning 'TABLE_PROD_RES' table...

Table: 'TABLE_PROD_RES' (1241211622); index ID: 1, database ID: 5

TABLE level scan performed.

- Pages Scanned................................: 748041

- Extent Switches..............................: 93526

- Scan Density [Best Count:Actual Count].......: 99.98% [93506:93527]

- Logical Scan Fragmentation ..................: 0.01%

DBCC execution completed. If DBCC printed error messages, contact your system administrator.

The WITH FAST doesn't mention the Avg. Page density which is needed if you want to REINDEX with a FILL FACTOR other than 100%, this is applicable if you table is updated quite often and is not static.

If not then 'WITH FAST' is much faster..thanks for showing this QUICK CHECK kinda thing..:)