Regular hulled barley has a fibrous outer hull that must be removed before consumption. The process of removing the hull is called pearling and the resulting product is called pearled barley. Hulless barley is essentially hulled varieties that are missing the 'cement' that connects the hulls to the bran and germ. The hull is still grown, but is predominantly removed during threshing. Because the hull comes off the barley naturally, it is considered a whole grain.

The preferred variety of Hulless Barley is CDC McGwire which was developed by Brian Rossnagel at the University of Saskatchewan Crop Development Centre. CDC McGwire is a two-row variety that has exceptional combination of disease resistance, yield, and thresh-ability making it a superior Canadian product that is exceptionally safe and provides significant health benefits for pets in a premium pet food.  Horizon sources and uses CDC McGwire barley in its Complete formulations.