This morning, after a suitable stool sample had been obtained, I packed her off to the vet's office. Dr. Grandrath saw nothing untoward in the stool (apart from its texture, of course), and the Parvo test came up negative (though it's possibly it's a false negative, there are few symptoms of Parvo: no fever, no bloody stool, no vomiting; just diarrhea and lethargy). The doctor agreed with my initial thought that this was probably caused by Rosie eating something gross at Ohlone Park on Friday. She gave us antibiotics and a recipe for mild food to rest Rosie's tummy. This means skipping puppy class this week, unfortunately, but Rosie's feeling so down that she'd have an awful time, anyway.
We're also going to wait to make sure she's not got Parvo before bringing her into a group of puppies with varying levels of innoculation.
For dinner, Rosie had a nice little homemade slurry of rice, tinned chicken breast, and cottage cheese (with REAL! LIVE! BACTERIA! -- it said so on the label).
(Recipe: make 3 cups of plain white rice. Mix in one can chicken breast and two large spoonfuls of cottage cheese. Feed in small doses throughout the day.)
Although the tinned chicken made the whole house smell something awful, and brought the cats to yowl around my feet in delight, Rosie seemed to take to the new food just fine, but then again she hadn't had anything to eat since breakfast, so she wasn't too picky. I followed some advice off the web and gave her a portion of an Imodium tablet, which had little effect; she still jumped up at 3am and asked to go out and have a liquidy, white poop.