When is the best time to feed my dog a, medium breed shih tzu to stop her pooping at night?

Feed your Shih Tzu in the morning and again at dinner time (5:00 p.m.). After you feed her, wait about a half hour and take her out to go potty. Keep her outside until she rellieves herself and then brag on her and make a big deal of her success. You might even try giving her a small treat. Positive reinforcement is very good for Shih Tzus because while they are very sweet dogs, they tend to be a little stubborn and self-directed. I also keep a 'puppy pad' out for my Shih Tzu. That way if she has to go in the night, she can do so without making a mess. She wants to please you, so help her out. And NEVER hit her. She's way too small to deal with abuse.