Alpacas chew their food which ends up being mixed with their cud and saliva and then they swallow it. Alpacas usually eat 1.5% of its body weight for normal growth. They mainly need pasture grass, hay, or silage but some may also need supplemental energy and protein foods and they will also normally try to chew on almost anything (e.g. empty bottle). Most alpaca ranchers rotate their feeding grounds so the grass can regrow and fecal parasites may die before reusing the area. Pasture grass is a great source of protein. When seasons change, the grass loses or gains more protein. For example, in the spring, the pasture grass has about 20% protein while in the summer, it only has 6%. They need more energy supplements in the winter to produce body heat and warmth. They get their fiber from hay or from long stems which provides them with vitamin E. Green grass contains vitamin A and E.
Alpacas can eat natural unfertilized grass; however, ranchers can also supplement grass with low-protein grass hay. To provide selenium and other necessary vitamins, ranchers will feed their domestic alpacas a daily dose of grain to provide additional nutrients that are not fully obtained from their primary diet. Alpacas may obtain the necessary vitamins in their native grazing ranges.
Alpacas, like other camelids, have a three-chambered stomach; combined with chewing cud, this three-chambered system allows maximum extraction of nutrients from low-quality forages. Alpacas are not ruminants, pseudo-ruminants, or modified ruminants.
Alpacas will chew their food in a figure eight motion, swallow the food, and then pass it into one of the stomach's chambers. The first and second chambers (called C1 and C2) are where the fermentation process begins. The alpaca will further absorb nutrients and water in the first part of the third chamber. The end of the third chamber (called C3) is where the stomach secretes acids to digest food, and is the likely place where an alpaca will have ulcers, if stressed.
Many plants are poisonous to the alpaca, including the bracken fern, fireweed, oleander, and some azaleas. In common with similar livestock, others include: acorns, African rue, agave, amaryllis, autumn crocus, bear grass, broom snakeweed, buckwheat, ragweed, buttercups, calla lily, orange tree foliage, carnations, castor beans, and many others.