i wouldn't talk to the manager in this case, s/he might just make it all nice and go away, besides I'm sure s/he is aware of the situation in there. report to SPCA, or in US it is probably called ASPCA, they have inspectors who are obligated to investigate all complaints, just call them and let them know. someone has told me that in US you can get a jail time for animal neglect, probably it depends on a level of it and state laws, but it is pretty serious.