Corn and other grains are ground in a hammermill to a fine meal. Particle size matters, because finer grinding damages more starch and changes how the dough cooks.

The ground grain is blended with meat and poultry by-product meals, fats, vitamins and minerals into one dry mix. Cheaper recipes use less meat and more grain.

In a preconditioner, paddles stir the mix while steam and water are injected. The meal heats, soaks up moisture and starts to soften before it reaches the extruder.

Turning screws drive the dough down a heated barrel, where heat, pressure and shear cook the starch into a melt. At the end it is pushed out through a shaped die, water flashes to steam so each piece puffs, and a spinning fly knife slices it off.

Wet kibble rides through a hot-air dryer until most of its water is gone. Dry enough, it keeps for months in the bag without spoiling.

The dried pieces tumble in an enrober that coats them with melted fat and a dry flavor powder. Taurine lost during cooking is usually added back after processing.

Coated kibble is cooled, screened to remove fines, and filled into sealed bags.