http://revach.net/article.php?id=4016

Section: Halacha   Category: Food
When Your Bracha Transforms The Food
The Mishna Berurah writes (167:97) that one may not give an animal, bird or non-Jewish person a piece of the bread that he recited the Bracha of Hamotzi on.  He explains that if one recited a hamotzi (as done typically on Shabbos) on a challah, one may not give a non-Jew a piece of that challah. 

The Piskei Teshuvos (167:29) quotes from the Sefer Chasidim that this halacha applies to any food or drink that a bracha was recited on and not just to challah.

The Piskei Teshuvos writes there are those who take this one step further and pasken that any food that was on a table while divrei torah were said, should not be given to an animal, bird or non-Jew.  This would seem to apply to a Shabbos seuda, where although a bracha is not made on any of the food other than the challah, since there is divrei torah said at the meal one should not give any of the leftovers from the table to an animal, bird or non-Jew to eat.