In Argentinian goat production systems, kids are weaned and sold between 45 and 60 d of age and weight between 10 to 12 kg. The aim of the present study was to determine average daily gain (ADG), and slaughter and carcass weights in Saanen kids slaughtered at 50, 60 and 70 d of age and fed ad libitum 3 diets: alfalfa hay (A), alfalfa hay + cracked grain (30:70, soya:corn) (AG) and only cracked grains(G) according to a completely randomized design. Twenty 7 Saanen kids were separated from their dams at birth and artificially colostrated. Throughout the experiment kids were fed with 1.5 l of goat milk twice a day. From the 2nd week of life, kids had free access to feed according to the assigned treatment. Kids were weighed once a week before milk supply. Immediately after slaughter, entire digestive apparatus was removed from the carcass. Data were analyzed with linear mixed model according to a repeated measures design by Infostat program. The Multiple comparisons were evaluated by LSD-Fisher test (P = 0.05). The weight at birth of the animals was similar between treatments (3.48 ± 0.51 kg, P = 0.42). ADG according to the diet was higher for those animals that consumed alfalfa, with or without grain supplementation (A: 147 ± 13 g - AG: 152 ± 17 g) compared with the grain group (G: 124 ± 20 g) (P < 0.01). Slaughter age did not affect (P = 0.96) ADG. Age affected (P < 0.01) body weight at slaughter; kids slaughtered at 70 d showed higher slaughter weight (12.83 ± 0.38 kg) than those slaughtered at 60 (11.32 ± 0.33 kg) or 50 d (10.08 ± 0.38 kg). Interaction between diet and age was not detected (P = 0.36) for slaughter weight. Kids slaughtered at 70 d of age had heavier (P < 0.05) carcass weight (5.11 ± 0.31 kg) than those slaughtered at 60 (4.61 ± 0.65 kg) or 50 d (4.10 ± 0.35 kg). Carcass weight tended (P = 0.06) to be greater in kids fed AG diet (4.88 kg) compared with those fed G diet (4.36 kg). No interaction between diet and slaughter age was detected for carcass weight (P = 0.78). In conclusion, obtained results indicate that diet only affected average daily gain, whereas age at slaughter affected both slaughter weight and carcass weight.