Guinea pigs benefit from a diet of fresh grass hay, such as timothy hay, in addition to food pellets which are often based on timothy hay. Alfalfa hay is also a popular food choice and most guinea pigs will eat large amounts of alfalfa when offered it, though some controversy exists over offering alfalfa to adult guinea pigs.
Some pet owners and organizations have advised that, as a legume rather than a grass hay, alfalfa consumed in large amounts may lead to obesity, as well as bladder stones from the excess calcium in all animals except for pregnant and very young guinea pigs. However, published scientific sources mention alfalfa as a food source that can replenish proteins, amino acids, and fiber.
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