soft bowel movements

Question
I have a re homed border collie been feeding him the recommend food that the vet advised but still got runny movement any advice on what else i can feed him thank you

Answer
Runny movements are seldom due to the food.  Has the vet checked and rechecked stool samples for parasites?  There is one other thing.  

If a dog is having trouble keeping anything down or continuing diarrhea try this out of the manual I have from a large, knowledgeable dog guide school.

Bland recovery diet for dogs.

3 parts cooked rice, one part boiled hamburger or chicken, or cottage cheese. I think you can substitute boiled potatoes for the rice. Once in an emergency, we bought a plain baked potato from Wendy's.

This is meant for short time settling a dog's digestive tract. It is not the complete and balanced diet they need long term. I have seen it work.

If that doesn't firm him up, the problem is likely parasites.  

If it does, it could be the food.  Most dogs will thrive on most foods, but no one food is right for all dogs.  If the vet's food is lamb based, try something different, chicken or beef.  I am not a big believer in immediately moving up the price scale to a grain free at the first sign of a problem.  There may be dogs that need a grain free food, but not near as many as are eating them.  

Over feeding can also lead to soft stools, but Border Collies are more likely to refuse to eat more than they need.  However, they are individuals, and none pay any attention to what I post.  Yours could be over eating.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them. Each dog is different. Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx