For health, ethical and environmental reasons, the sales of grass-fed beef have shot upward in recent years. But the nutritional makeup of your pricey steak may depend on when the cattle finished up on pasture.

Food scientists from Michigan State University discovered that grass-fed beef sourced from four producers representing several regions in the U.S. typically had higher amounts of desirable omega-3 fatty acids when the cattle were grass-finished in the spring rather than the fall. This was also true for the two antioxidants vitamin E and selenium.

The reason for the nutritional discrepancies is not yet fully understood, especially considering that some producers use the exact same pasture feed in both seasons. But if you source your grass-fed beef from a local producer, it seems like a nutritional win to go for those early-season cuts.