Wal-Mart, which announced in March that it will add 400 organic SKUs to its product mix, is now expanding on that promise. As of mid-May, about half of all Wal-Mart stores will also carry natural dog and cat food.

Wal-Mart spokeswoman Jolanda Stewart said her company will stock four SKUs of Natural Life pet food in the 1,500 stores where Wal-Mart research shows consumers "tend to purchase products with organic and natural tie-ins." Wal-Mart has a total of 3,189 stores.

Natural Life will be the only natural or organic pet foods Wal-Mart carries, although Stewart said the discount retailer could add more natural pet products and brands in the future.

Stewart said Wal-Mart chose Girard, Kan.-based Natural Life pet foods because "they came to us with a formulation that met our specifications." She wouldn't reveal those specifications, but Wal-Mart has previously publicized that Natural Life pet foods are made in a certified organic facility; have no artificial preservatives, colors or flavors; don't include animal byproducts; and contain chelated minerals.

Natural Life President Patrick Mendick said his company's dog and cat foods are "natural, high-end, quality products" and that Wal-Mart was "looking at more upscale products in its stores." He said the Wal-Mart contract hasn't affected his company's manufacturing operations, and it's too soon to tell how it will influence his sales.

Natural Life is carried in many natural foods stores. At a Denver Whole Foods Market, an 8-pound bag of Natural Life adult dry dog food retails for $12.99; at Wal-Mart it will retail for $10.32. At waggintails.com, the same product sells for $10.59.