Heparin and rabbit ear bleeds?

[Paul A Bucciaglia]

When using vacu-tainers to bleed rabbit ear arteries, we use 
heparin to increase blood flow and avoid clotting in the syringe.  The 
collected blood does not form a clot; the cellular debris is 
centrifuged out and serum is diluted and generally used for western 
blotting.  Overall, we haven't had much success generating antibodies.  
Our boss has raised antibodies in the past, collecting serum thru cardiac 
puncture, allowing the blood to clot and then removing the clot.  He has 
suggested that clotting is important for getting clean antibodies.  Can 
anyone shed some light on this debate?  Is clotting necessary? Does it 
remove whole blood fractions that might interfere with western blotting?

Thanks,
paul bucciaglia