parts of dog poop is white on the outside

Question
Hi, i have a teacup sized maltese. wondering if you can tell me what it means when parts of her poop is white. the white is only on the outside, the inside is greenish.

We used to feed her Iambs small chunks, but now changed it to Nutro brand (lamb meat and rice meal). We changed it because we were told by the people at the petstore that Nutro is better because Iambs is a corn based filler and Nutro is meat based (better nutrition). Is that true?

Everything else is normal, just concerned about what the whiteness on the poop could mean.

Thanks for the help. :)

Answer
Hello Mike,
I have to be honest with you, I really do not know the answer to your "poop" question.  Regarding the Nutro brand of dog food, the people at the petstore are correct.  Nutro is very good food. Perhaps the change in diet has caused a bit of a discoloration.

God Bless,
Becky