It is reported to work very well. There are several repellents manufactured with blood meal as the primary active ingredient.

It not only is a deterrent for deer and rabbits, but It can also be used as an activator in compost bins, as it it high in nitrogen, but so is Rabbit manure.
Interestingly though, I have found several places where articles and pieces in hort books have mentioned thinking twice in using Blood Meal in regards to the possible comtamination from BSE (Bovine Spongiform Encephalopathy aka Mad Cow Disease). Haven't research this thoroughly, but thought it a bit fyi-ish.
Best,
PP

I am trying a deer repellant that is primarily blood meal. It is supposed to last for several months, even if it is rained on. The product is called Plantskydd , meaning plant protection in Swedish.
I don't like it because it is very messy and a lot of trouble to get ready to spray.
Jerry