Oyster shell is primarily calcium carbonate. It’s often crushed for use in bird food & chicken feed as calcium-rich grit. It aids digestion and contributes to egg health. Crushed oyster shell is also used in aquariums to stabilize and increase pH. This environmentally friendly, natural solution puts to good use what would otherwise be a waste product from the human food industry.
Oyster Shell for Birds & Chickens
Grit is important to birds & chickens as it’s used for efficient digestion. It may serve the purpose of helping to grind the food, but there is some misunderstanding there. When science tells us a bird uses grit to aid in digestion, they aren’t only talking about the mechanics of digestion.
To truly digest food, the animal must absorb the nutrients and that’s considered to be part of the digestion process. The process doesn’t end at the gizzard/stomach. It continues through the lower digestive system, where the uptake of minerals from the digested grit can occur. Grit also slows down the process, allowing food to stay in the digestive system long enough for nutrient uptake, yet serves a purpose similar to fiber in moving everything through.
Sometimes our captive birds don’t seem to require grit, after living many years without it. A possible explanation is that captive diets are often more easily-digested or soft.
Louis B. Best of Iowa State University studied grit preference for 22 bird species. The study concluded that birds can be quite selective in what they desire in grit, inadvertently indicating that grit does indeed serve a necessary purpose and it is intentionally ingested. Definite preferences were observed in regards to preferred size, shape, surface texture, ingredients and even colour. White, green and yellow grit (all shades found in oyster shell) were consumed most, with black and blue being the least favorite. A strong preference for silica was demonstrated, while gypsum and corncob grit received two wings down. Providing a range for your birds to select from will eventually reveal their preferences to you.
Oyster shell should be viewed as a calcium supplement for a grit mix, as opposed to grit itself. It’s sometimes used in combination with other types of grit or mixed with food. Laying hens utilize the calcium in oyster shell to produce healthy, strong egg shells.
Free range chickens should pick up enough grit for digestive purposes through outdoor feeding, while penned or indoor birds should have a grit supplement. In either scenario, laying birds will greatly benefit from a diet that includes oyster shell and other natural sources of minerals.
Adding oyster shell to an adult bird’s diet is as simple as that – add it. It can be fed separately, sprinkled on the ground, mixed with grit or silica (clay sources of silica are packed with other benefits), or mixed sparingly with food for adult chickens. While chicken egg shells are also a wonderful dietary supplement, they have to be thoroughly cleaned to prevent bacteria accumulation. Additionally, the mineral content of chicken shells is determined by the diet of the hen that laid them. If the laying hen isn’t properly nourished, the shells of their eggs won’t be either.
Healthy, adult birds instinctively eat the amount of grit they need, averaging up to 5 ounces/month for chickens and up to 10 ounces/month for turkeys. The smaller the bird, the smaller the grit size range. Some birds have a wide range of grit sizes in their gizzard (common in birds preferring larger grit), while others consistently pick up similar sizes. Studies have found birds that prefer smaller grit have had more grit in the gizzard. Youngsters sometimes lack good judgment and should have their grit intake controlled. A light sprinkle on their food should suffice. Occasionally, health issues will cause a bird to take too much grit, so you may prefer to control the amount for adults as well.
Oyster Shell for Aquariums
Aquatic pets that require a higher pH and/or love alkaline water, will respond positively to the addition of oyster shell in their environment. It’s perfect for healthy, smooth shell development in snails. Cichlids, Livebearers or other fish that require higher levels of pH and alkalinity will thrive. Not only will it contribute to an optimum environment, but it also adds stability to that environment by increasing KH (buffering) levels. This helps to prevent deadly pH fluctuations and system crashes.
Oyster Shell is considered to be superior for buffering due to it’s particle size & shape, which allows for aeration and graduated dissolution. Another great thing about oyster shell is it dissolves noticeably as it depletes. Unlike coral, you don’t have to guess when it’s time to add more. Pour some into a media bag (or nylon stocking) and add it to your filter or other source of water movement. Add more when you notice that it’s low and that’s all there is to it.
Like anything that impacts pH, oyster shell should be added in small increments until the desired parameters are reached. Using too much, too quickly will cause a dramatic change in pH, which can harm your aquatic livestock, plants and beneficial bacteria. It is recommended that you add a small amount every few days to a week and test the water parameters until you reach the desired levels. Please familiarize yourself with aquarium chemistry before using any pH adjuster.
Note: Oyster shell or any buffering media should be cleaned periodically to ensure optimum efficiency. Use aquarium or dechlorinated water to rinse without losing beneficial bacteria.
For more information about how to manipulate aquarium pH, please refer to our post, Increase Or Decrease Freshwater Aquarium PH Naturally.
Crushed oyster shell should be ‘feed grade’, which has a much higher standard for purity than pet grade (or unrated) oyster shell products. Any item that will be fed to animals intended for human consumption (or if they produce food for human consumption, as with eggs) is more strictly regulated. We encourage you to ask retailers if their oyster shell product is feed grade before purchasing.
Best, Louis B. Grit Use Behavior in Birds. Dept. of Animal Ecology, 124 Science II, Iowa State University, Ames, IA.
✔ You may also be interested in reading:
15 Natural Feed Supplements for Birds (Exotic, Poultry, Pigeons, Waterfowl, Etc.)
Natural Fish Foods and Supplements for Fancy Fins
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