How much apple and yogurt can my golden retriever eat daily?

Dogs don't need apples as part of their daily diet, but they are a relatively healthy treat as long as you make sure to remove the seeds. So you can give him a piece of apple every day if you want to - I would not expect this to cause any problems.

A maintenance diet would be 1 cup (8 ounces) of dry food per 30lbs body weight daily. For example, if Rooney weighs 60lbs then he would need 2 cups of food daily. This amount can be adjusted up or down based on activity, body weight and body condition.

It really depends on why you're given them. If Bella is on a well balanced quality dog food AND an ideal weight, she should be getting about 700 calories a day and no more than 10% (70 calories) should be coming from treats. So the cup amount would depend on the food (70 calories = 3/4 cup blueberries or pumpkin puree, or a little over a cup of cubed apples). On the other hand, if you're not giving her mostly dog food, I'd recommend using this website to build a balanced diet and order a supplement. https://secure.balanceit.com/recipegenerator_ver4/index.php?rotator=EZ

Yes, both of these foods are safe for dogs - there's no reason that you couldn't give them every day, in small amounts as a treat. Just make sure that you're not using a sugar-free brand of peanut butter, as some of these contain xylitol which is toxic for dogs. Most "regular" peanut butter brands are fine :)

You should feed her according to the instructions on the food label as it it differs from brand to brand. regarding her eating her feces, it's very common in puppies but should be discouraged of course, there are many supplements that you can find in pet shops that can help with this problem, one example is called "deter", it makes the poop very bitter and dogs usually hates the taste.

I calculate about 1,400 kCal per day for a moderately active 75 lb dog with an ideal body condition. An overweight dog who is a couch potato would need fewer calories. The appropriate amount of fat varies but is usually between 20-30% of the calories. Unless Rowen requires a very low fat diet I probably wouldn’t worry about the extra fat from the fish oil. The appropriate dose depends on what you’re using it for and the EPA and DHA contents of the particular capsule.

In general I don't recommend to give yogurt to dogs because dairy tends to upset the stomach. If Simba seems to really like yogurt and it does not cause him to have diarrhea or an upset tummy, you can give him a small amount as a treat (no more than 1 teaspoon). I hope this helps and please feel free to post any additional questions.