Here is another discussion on this topic:
http://ohr.edu/2261/printFrom: Avi
Dear Rabbi,
I read the article Kosher Keeping Pets. I was wondering if the dog food was glatt kosher, can a Jewish person partake in the eating of this highly nourishing delight, or does it just mean that there is no milk and meat in the process. Thank you.
Dear Devorah and Avi,
Identity crisis issues aside, the point of the article was that pets of Jews are not Jewish pets. This means that while a Jew may not eat non-kosher food, he may feed most non-kosher foods to his pets.
The few exceptions are those foods that are not only non-kosher, but are also prohibited for a Jew to derive any benefit from. Since the Jewish pet owner benefits by, and enjoys keeping his pet alive through feeding it, the pet food must be something that the owner, as a Jew, is allowed to derive benefit from.
Two such exceptions of foods which are not only not kosher, but are also forbidden to derive benefit from, are mixtures of meat and milk during the entire year, and chametz during Passover. A Jew is prohibited from feeding these foods to his pets at those times not because they cant eat them, but because he cant give it to them.
Therefore, glatt kosher pet food would only ensure that the owner can feed it to his pet, but not that its kosher for a Jew to eat. Unfortunately youll have to stick with chopped liver and cholent. "Kosher" pet food only means with no meat and milk, or chometz on Passover.