The Association for Pet Obesity says 53% of dogs and 58% of cats in the US are overweight, and 90% of pet owners don’t know their pets are overweight.

A recent study found that pet food particle size can affect digestibility. In the study, 54 beagles were fed maize, rice or sorghum in fine, medium or coarsely ground nuggets. Size made a difference in the maize and sorghum nuggets, but not rice.

Researchers said: “if properly processed, maize and sorghum are as easily digested as rice-based food,” and that dog food companies should examine reducing particle size.

The research found rice is easily digested and the processing doesn’t matter as much. But maize and sorghum are "dependent on a proper raw material particle size and need to be appropriately extruded to produce highly digestible foods."

A problem in the extrusion process is that most pet food manufacturers “have only one grinding condition for all recipes, and do not change the extrusion size based on the type of cereal used.”