Humane societies get alot of food donated.. So it could be Science Diet or it could be Ol' Roy. And even Science diet has gone downhill lately with all the crappy grains they are putting in the food.

Try the highest quality you can get, they eat SO much less of it(adult males need about 1/4-1/3C a day and are fine) and poop less as a result. Fillers such as grains just make their poo smell worse, as well as make their hair coat rough and oily.

Wellness, Felidae, Innova Evo, Solid Gold, Bil-Jac (is actually good from what I've read in the ingredients), and a few others. They may seem more expensive, but your cat will live a much longer life and will not have the health problems associated with a poor quality diet(especially at the start of life).