Giardia Meds and Nutrition!

Question
My 6 1/2 month old Shih Tzu rescue was just diagnosed with Gastric Ulcers and tested positive for Giardia after being taken in with vomiting blood and soft, light tan colored stools accompanied with Mucus.
My vet placed her on several meds and antibiotics to help treat the Ulcer, cease the vomiting, and includes a treatment for the Giardia as well.
My question is two fold..
#1...I was thinking about adding some digestive enzymes and a probiotic to her diet, as I feel she could use this to help rebuild her immune system, digestive tract, etc..and heard about giving Activia Yogurt to dogs...is this safe? And if yes, how much, how often should I feed it to her. She is only 5.5 pounds in weight and eats 3 small meals per day! She is being transitioned off bland food to Nature's Variety Prairie Salmon formula Kibble and her stools are getting failry soft, light tan in color and have a grainy texture to them again. Her stools firmed up and darkened while on the Acid Blocker meds, but she finished those 2 days ago and now they are turning back to the same stool consistency and light color as before!
and
#2...I have two other dogs, a 14LB Peke and a 12LB Tzu and though neither are showing signs of being infected with the Giardia, I am worried about them and was wondering, would it be in their best interest to treat them with Panacur as a preventive measure?
I suggested to the vet to have them tested and she didn't feel it necessary as they weren't showing signs, but the meds my baby Tzu is on currently,(Metronidazole), I have read that it actually only has about a 40% success rate in treating the Giardia and that it can reoccur shortly after the meds have been stopped.
Please advise?? Thank you!!

Answer
Hi Vicki,

First of all, although I have worked for a vet in past and have seen many cases of Giardia both in that capacity and  in my work as a nutrition consultant, I really feel uncomfortable advising on veterinary issues. If these were my own dogs? I would ask for the test, and also to have the  Shih Tzu re-tested.
Now, the questions I CAN answer. With gastric ulcers I would never add  digestive enzymes as they can exacerbate the sores. There are some products you could consider - supplemental, short term zinc, licorice, slippery elm and aloe vera (should be used under supervision from an experienced herbalist or a vet trained in herbalism) but not enzymes. Using plain yogurt may or may not upset her stomach, I would steer clear and add a probiotic, but concentrate on healing the ulcers.

you can rebuild the immune system by restoring healthy absorption of nutrients/healing the intestinal tract, and adding a digestive enzyme will likely worsen the ulcers.

Please do get a second opinion on the Giardia, it can be very difficult to clear up, and dogs should be re-tested, IMO, and the others tested as well.
All the best, Catherine