Adult Guinea Pig Food is made from timothy grass meal, which includes the high fiber adult guinea pigs need. However, it contains a lower level of protein, calories and calcium than alfalfa-based pellets. Adult animals' digestive systems do not require the same level as that of younger animals. Young Guinea Pig Food is alfalfa based and specially designed to provide high fiber, protein, calcium and energy required for young guinea pigs to thrive. The optimized, balanced protein and stabilized vitamins also help nurture pregnant and lactating animals.