A comparison of food selection and foraging behavior in juvenile and adult goats

Young animals face unique constraints in foraging on rangelands. They are at an inherent disadvantage to older animals because they have higher nutritional requirements and they lack foraging experience. Comparisons were made in diet selection, foraging time and weight changes for adult (does) and juvenile (kids) goats foraging at two stocking rates (heavy vs. light) during the winter of 1979 on rangeland dominated by blackbrush ( Coleogyne ramosissima). The previous experiences of adult and juvenile goats differed because does had browsed blackbrush during the winter of 1978, while kids were raised from birth until 6 months of age on alfalfa hay. Does and kids in the heavily stocked pasture consumed diets that were similar in percentage blackbrush (95 vs. 94), blackbrush leaf:stem ratios (0.44 vs. 0.45), crude protein (7.2 vs. 6.9%) and in vitro digestible organic matter (39.3 vs. 39.2%). Does and kids in the lightly stocked pasture consumed diets that were similar in blackbrush leaf:stem ratios (0.41 vs. 0.42) and crude protein (6.6 vs. 6.6%), but does consumed diets that were slightly higher ( P = 0.039) in percentage blackbrush (94 vs. 88), but lower ( P = 0.028) in in vitro digestible organic matter (36.0 vs. 39.5%). Kids spent considerably more time foraging than did does ( P < 0.0000) in both the heavily (59 vs. 41%) and the lightly (65 vs. 47%) stocked pastures. Kids also lost a greater percentage of body weight ( P = 0.02) than did does (22 vs. 17).