Blood sacrifice has always been how mankind has overcome the debilitating power of sin.  Since the Garden of Eden, we see how blood had to be shed to restore fellowship with God.  Animal blood was shed to cover sin.  Our God is a Holy God, and the Blood of Jesus erases the sin in our life so we can have fellowship with Him.  Our enemy, the devil, has tried to manipulate and mock blood sacrifice practice.  For us, there is power in the Blood of Jesus.  There is no longer a need for animal blood to be shed to atone for sins.