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Pellets
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Powder
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Pellets are easier to feed than powder. Pellets can simply be thrown on top of the cage or even inside. Its easy to monitor the pellet supply and assure that animals have 24/7 access to feed.
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Powder requires special feeders. The feeders can be easily tipped and spilled, and the food can also be easily soiled by urine, feces or even saliva. So it is difficult to assure that the animals have 24/7 access to good clean food.
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Pellets are a stable food stuff. They can be stored for months without losing quality.
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Powder has much greater surface area and the food spoils much easier. Powder also has a less obvious problem in as much as powders can become ‘unmixed’ over time. That is, smaller, more dense particles may sift to the bottom and less dense, fluffier parts may sift up, making the diet no longer homogenous and in the extreme nutritionally incomplete from top or bottom.
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Pellets are homogeneous.
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Powder can be separated by the animal by pawing, sniffing and snorting, either intentionally or inadvertently.
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Once pelleted compounds are ‘frozen’ in place and won’t become unmixed. Also the test compound is more stable in pellets as most of it is inside the pellet and away from direct air, light and humidity which cause most of the degradation of test compounds.
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Powder is often used by facilities that lack the equipment, personnel, money or interest in pelleting food. This is often done when researchers want to add test compounds to feed. Test compounds can easily sift out of the powder.
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Pellets are dustless and cannot be inhaled.
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Powder can be (or is) inhaled by feeding animals causing respiratory irritation and infections. This is an often overlooked problem with feeding powder diets. This is especially likely with powders of standard chows, which unless irradiated are loaded with microbes.
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Feeding pellets helps ‘wear’ incisors down.
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Powder fed rodents may develop overgrown incisors
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