Sigma sells BSA of very high molecular biology purity which works well for
IHC work. Some year back, John Tarpley discussed BSA on Histonet, you might
want to check archives for his comments. 

For our large animal other than bovine work (I tend to avoid BSA with
bovine)  we buy Jackson ImmunoResearch's BSA that is immunoglobulin and
protease free.  For IHC on bovine, we prefer normal serums matched to host
of secondary antibody or try swine, goat (donor herd, pooled from Sigma) or
horse serum.   All normal serums are heat inactivated to get rid of
complement at 56C for 30 min to 1 hour, cool and microfilter into a sterile
centrifuge tube. 
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

email: gcallis@montana.edu