T.S.
I'm sorry you have to deal with this. Violent tantrums, like the ones youre describing, are difficult for both the child and the parent. There are many causes for tantrums, from average toddler tantrums to violent ones like you're describing. Your daughter's new experience with day care could be a prime cause, it could be over exhaustion, health related, or any number of things. You know your child best so no matter what anyone here says, only you can be the one to figure out the best route to handle this with her. I highly suggest reading up on violent tantrums, not only for the information that may be helpful but also because tantrums containing this kind of violence are regular indicators of other problems such as developmental problems, behavioral disorders, etc. I'm not saying that your daughter 'has something wrong' with her, I'm only saying that it would be wise to cover all of the information and make a judgement call as to whether this is caused by the average tiredness issues or something more. There is a great article, that was published in many psychological journals last year. It was put out by Colorado Univ. You can read the original article at http://www.ext.colostate.edu/PUBS/CONSUMER/10248.html
Cigna also has a wonderful resources at http://www.cigna.com/healthinfo/hw170047.html#hw170084
Another great article was put out by CES, http://www.ctahr.hawaii.edu/oc/freepubs/pdf/CF-7.pdf
I hope that you find a resolution to her tantrums soon. I know this is draining, emotionally and physically, for your family. I'm sorry you're going through this.