The term 'trough fill' refers to the process of filling a trough with FEED or SLOP. FEED is a type of food given to animals, usually in the form of grain, hay, or other plant-based materials. SLOP is a type of food given to animals that is made up of a combination of grains, vegetables, and other ingredients. Both FEED and SLOP are used to provide nutrition to animals, and the trough fill process ensures that the animals have access to the food they need.