Nutritional value and intake of prickly pear by goats

Prickly pear (Opuntia sp.) is both a benefit and hindrance to the livestock industry in the southwestern U.S. It competes with herbaceous forage but is sometimes used as emergency feed during drought. Spineless prickly pear (0. fiscus-indica Engelm. and 0. rufida Engelm.) has been planted in some regions of the southwest but little is known about its nutritional value. Our objectives were to determine: (1) the nutritional value of both spined (0. macrorhiza Engelm.) and spineless prickly pear (0. rufida Engelm.); (2) if goats can be conditioned to eat prickly pear after prescribed burning; and, (3) if goats would consume prickly pear when alternative forage was available. In Experiment 1, 8 goats were placed in metabolism stalls and fed either spineless or spined prickly pear with singed spines in both summer and winter. Intake, digestibility, and nitrogen balance were measured. In Experiment 2, 18 goats were placed in individual pens, and 9 were fed spineless prickly pear to determine if this increased acceptance of spined prickly pear with singed spines. In the third experiment, we varied the amount of alfalfa pellets fed to goats (below, near, and above maintenance) to determine if level of alfalfa intake affected prickly pear intake. Spineless prickly pear was higher (P < 0.05) in digestibility and crude protein than singed prickly pear, but nitrogen balance was similar for goats consuming the 2 species. Goats ate more spineless prickly pear on an as fed basis, but on a dry basis, intake was similar. Familiarity with spineless prickly pear increased (P < 0.05) subsequent intake of singed prickly pear. Level of alfalfa intake did not affect prickly pear intake. We concluded that both species are moderately nutritious, spineless prickly pear is more digestible than spined prickly pear, and once a preference for prickly pear has developed, goats may continue to eat prickly pear even though other forage is available.