Lamb from New Zealand and Australia is most likely grass-fed lamb. American lamb is usually grass-fed and sometimes grain-finished to give the lamb a more mellow flavor. It's a personal preference for whether or not you buy grass-fed or not. It's more of a flavor preferences since the nutritional value of grass-fed vs. grain-fed beef is quite negligible. For example, grass-fed beef is often promoted as having more omega 3s. While that is true, grass-fed beef has about 5% of the RDA for omega 3s compared to 4% RDA in grain-fed beef. (P.S. You might notice that some photos have grass-fed beef. It was chosen simply because it came in the same type of package as the lamb. The nutrient analysis is done on regular beef. And as a dietitian, I buy grain-finished beef unless grass-fed is the only option)