He states on his website, "The materials and luminosity in these bodies of work relate to themes of corporeality, mortality, spirituality, and science—invigorating blood as sublime."
He is supposing that by using cows' blood, the viewer will suspend their disbelief, and instead interject their own corporeality into his works. On one hand, I understand him using a "substitute" material i.e. cow's blood to invoke a human's issues with mortality, however in the end, it is merely a substitution for the "real" thing. I believe human blood would be more powerful and a closer, more authentic experience.
On the other hand, I have wrestled with these same issues in my own artwork and sometimes there is the problem of acquiring "authentic" mediums such as human blood, bones, etc., so I am sympathetic to this dilemma.