The objectives were to investigate if partial substitution of a grazing diet with a supplemental high-starch feed during the last 12 d of gestation improved colostrum yield and neonatal activity in goat does grazing semi-arid rangeland. For the first objective, 25 pregnant does were randomly assigned to 1 of 2 treatments: 1) grazing only (control; n = 11), and 2) grazing plus 0.6 kg/d of supplemental corn (as fed), a high starch feed, during the last 12 ± 1.0 d before parturition (SC; n = 14). Colostrum was collected at parturition and again at 1, 3, 6, and 10 h postpartum for yield and composition. In all goats, blood concentrations of glucose and plasma progesterone were determined. Total colostrum yield/10 h was greater (P = 0.002) in the SC does (1,102 ± 144 g) than in control does (405 ± 50 g). From 6 to 10 h postpartum, contents of colostrum protein and solids not fat were less (P ≤ 0.012) whereas lactose contents were greater (P = 0.035) in the SC does than in control does. Concentration of glucose in the blood at parturition was greater (P = 0.037) in the SC does (160 ± 13 mg/dL) than in control does (115 ± 12 mg/dL). A significant decrease (P = 0.001) in plasma progesterone concentrations occurred 1 d before parturition in control does, whereas the decrease (P = 0.008) occurred 3 d before parturition in SC does. For the second objective, 20 does (10 per group) and their single kids were randomly assigned to the same treatments as above for evaluation of dietary treatment on neonatal activity. Kid activity was assessed using videos recorded during the first 90 min after birth. Frequency of low-pitched bleats was greater (P < 0.001) in kids of SC does than in kids of controls. Frequencies and durations of teat seeking from 30 to 90 min after birth and of suckling activity were greater (P ≤ 0.015) in kids of SC does than in kids of controls. Duration of parturition was longer (P = 0.001) in control does (58 ± 10.2 min) than in SC does (21 ± 2.8 min). Finally, percentage of fetal malpresentation was greater (P = 0.036) in control does (33.3%) than in SC does (9.0%). We conclude that partial substitution of the grazing diet with a high-starch feed, corn, during the last 12 d of gestation improved colostrum yield and neonatal activity in goats grazing subtropical semi-arid rangeland.