I assume that you mean sheep albumin and not BSA (bovine serum albumin). Usually, this problem is resolved by application of immunoaffinity depletion (immunoaffinity subtraction). Such columns are available for human serum. Systems are sold by Agilent and others (see links below).

However, the most critical point in your case is the fact that you want to remove sheep albumin and not human albumin. I do not know a system to perform immunoaffinity depletion with sheep serum. Perhaps some kits against human proteins might have a sufficient cross-reactivity against the respective sheep protein(s). Please also consider the relatively high cost of such depletion kits. You also may consider developing your own antibodies against sheep albumin, e.g. in rabbits or chicken.

https://www.ncbi.nlm.nih.gov/pubmed/18369884

https://www.ncbi.nlm.nih.gov/pubmed/16212426

http://www.sigmaaldrich.com/life-science/proteomics/mass-spectrometry/protein-aqua/absolute-quantification-of-serum-proteome.html

https://www.agilent.com/cs/library/applications/5989-7839EN.pdf

https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/General_Information/vol_issue22_proteoprep20.pdf

Hi Bouchra, in addition to the above suggestions, Thermo-Fisher sells a BSA removal resin called Melon.

My collaborators are very happy with it.

https://tools.thermofisher.com/content/sfs/brochures/TR0055-Melon-Gel-for-BSA.pdf

Dear Pr Weller, many thanks for your reply. Yes I would like to remove sheep albumin. I am trying to developp a simple test for ealy pregnancy diagnosis. I tried double immo diffusion. I tried western blot but in this case my proteins of interterts have the same MW of albumine and in western blot I don't not see any reaction. Please, could you give me your email adresse I would like to discuss more about the subject. Best regards

Bouchra