Would you accept a bag of Blue Buffalo Senior dry dog food as a donation?

You will probably have to call them directly, but I don't know why they wouldn't?

As long as the bag of food has not been opened they shouldn't have any problem accepting it and giving it to another poor baby who doesn't have anything to eat. But if it has indeed been opened they might simply throw it away because in the past people have donated opened bags of food with the sole purpose of poisoning the animals. For this reason, no animal shelter in any part of the world would ever accept opened bags of food with ecuanimity.