We use 3 kinds of Guinea Pig Pellets. The label is under the control of feed officials who sample feeds and run analyses to see that whatever the label carries is really included in the feed.
Most states require minimum protein, minimum fat, and maximum fiber to be listed on the tag.
Unfortunately as a result this is often all that is guaranteed on the tag. Protein is one of the more expensive components of a feed, yet it is critical for growth, lactation, and muscle recovery and development. The chemical analysis simply gives information about the total amount of protein but does not account for the digestibility of amino acid composition. As an example, corn gluten meal has low digestibility for horses as well as a poor assortment of amino acids, indicating this source of protein would not be good for young, growing horses. Linseed meal has been widely used by the horse industry, but it is usually quite high in indigestible fiber, and the protein is of relatively low quality.