LOS ANGELES (CBS) — Various meat labels approved by the USDA have left many consumers confused and questioning their true meaning.

According to the USDA Marketing Service standards, “100% Grass Fed” grass-fed cattle exclusively feeds on grass and forage plants, like hay, for their lifetime. They must have access to pasture and cannot be fed grain or grainbyproducts. If the label only reads “Grass Fed,” the meat may contain antibiotics from grain being fed to the animals as well.

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“Free Range” labels, by law, mean the animals have access to the outdoors; health officials say that could mean a small entrance to a long barn the animals may not even use.

“Tens of thousands of chickens are not going to come pouring out of the door. They’re all going to cluck at one another and then you can shut it after five minutes. You can legally then call all of those chickens free range,” said Urvashi Rangan of the Consumers Union.

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A “Natural” label means the meat contains “no artificial ingredients or added color and is only minimally processed,” according to the USDA.

“No Hormone” or “Hormone Free” labels indicate that the producer has shown documentation proving no hormones were used in raising the cattle. “No Hormones Added” labels may not be used on pork or poultry unless it is followed by a statement saying “Federal regulations prohibit the use of hormones,” according to USDA.

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Grocery chains like Whole Foods are developing labels on meat products to help consumers better understand their choices.