As to the original question, yes, a 45# bow has plenty of snot to kill deer. As others said, it's not simply poundage. It's shot placement, arrow flight and broadhead type. An arrow kills by cutting, not kenetic energy. A heavier bow doesn't shoot that much faster, it mainly handles heavier arrows better. Heavier arrows will give better penetration, at least in traditional bows. A properly tuned 40# bow kills better than a lousy setup in 70#s. I use a 70# longbow with about 700 grain sticks. It's accounted for much larger stuff than whitetails and is, of course, slower than a compound. I use a 50# recurve for deer and shoot through them time and time again.