Is one absolved of responsibility by placing food from a garbage bag on the side of the road for animals to eat?

A Muslim is religiously obligated to preserve the bounty of food, out of respect for it and gratitude to Allah. This includes bread and other foods. Edible food fit for human or animal consumption should be preserved. There is no sanctity for spoiled food that cannot be utilized. What you did by removing the bread from the road and preparing it for animals is an act for which you will be rewarded, and it absolves your responsibility, as it is the utmost that can be done to preserve food that has been thrown into the trash.