Sifted to 1/4 minus, perfect for chickens, ducks, turkeys and all laying birds or poultry. Untreated and without any additives or medication, straight from the Oregon coast. Basics for the backyard flock, whether you are tending a backyard flock or breeding champion show birds, Oyster Shell is a must-have. HENS NEED PLENTY OF CALCIUM TO LAY HARD-SHELLED EGGS. THEREFORE, GIVING HER OYSTER SHELLS IS AN EASY WAY TO BOOST HER CALCIUM LEVELS. Here are a few reasons that your flock benefits from calcium found in oyster shells: * Reduces the risk of eggs breaking * Reduces the risk of bones breaking or any bone damage * Strengthens blood vessels * Protect your chickens' immune systems * Non GMO, 100% natural * Recommended for laying hens * Good source of calcium for strong eggshells.