Alpacas eat a variety of low protein hay and pasture grass. These animals are ruminants that effectively use any available nutrient supply. They also enjoy plants that have long fibres as well as good pasture and commercial alpaca mixes.
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An alpaca's diet varies somewhat depending on what region it lives in, but in general 80 percent of its diet should come from hay or pasture grass. Pasture grass should be tested for its protein content. You can find more information here: http://ezinearticles.com/?What-Do-Alpacas-Eat?&id=1186357
Alpacas do well with eating pasture grass and hay that is of good quality. They are fine with eating a mixture of grasses such as bermuda, bahia, orchard, and other grasses.