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.
A complete feeding guide for Abyssinian guinea pigs: the right hay, vegetables, pellets, and tips for keeping your rosette-coated cavy healthy and well-fed.
Young guinea pigs on alfalfa based pellets (which include most available brands) do NOT need any extra alfalfa hay!Stay off alfalfa hay and feed readigrass only in pinches as an occasional treat. It is too rich for regular feeding.
For younger guinea pigs, alfalfa hay can be given in moderation due to its higher nutritional content. However, as they reach adulthood, its best to transition them to Timothy hay or orchard grass hay to maintain a healthy diet.
Timothy Hay vs. Alfalfa Hay for Rabbits & Guinea Pigs.Timothy hay is one of the most common options. Alfalfa may still have a role in some feeding plans, but for average healthy adults it is generally not the main hay source.

Risks of Feeding Dog Food to Guinea Pigs. Common Household Items Guinea Pigs Might Try to Eat.Alfalfa hay is good for young, pregnant, or nursing guinea pigs because it has more calcium. But, adult guinea pigs should avoid it because it can cause bladder stones6.