Age and weight of meat goats vary considerably, and little knowledge exists concerning differences in growth, efficiency of feed use, and carcass characteristics of goats slaughtered at different times. Fourteen Boer x Alpine kids (14±0.6 kg initial body weight) were used to determine effects of feeding from 15 to 31 wk (Phase 1) and from 38 to 50 wk (Phase 2) on feed intake, body weight (BW) gain, feed efficiency, plasma constituents, internal organ mass, and carcass traits. All wether kids

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... sumed ad libitum diets with 20 and 16% crude protein and 33 and 40% neutral detergent fibre diet in Phase 1 and 2, respectively. Body weight after Phase 1 and 2 was 42±2.0 and 57±0.8 kg, respectively; BW gain was greater (PO.01) in Phase 1 than in Phase 2 (228 vs 118 g/day); and the ratio of BW gain to dry matter intake differed (P<0.01) between phases (0.19 in Phase 1 vs 0.10 in Phase 2). Cold carcass weight (20.4 vs 29.6 kg; PO.01), dressing percentage (50.1 vs 56.5%; PO.01), and percentage of carcass fat (16.4 vs 20.2%; P = 0.09) were lower after Phase 2 than Phase 1, and leg cut percentage (30.5 vs 28.3%; P -0.07), carcass bone percentage (23.7 vs 20.6%; P = 0.01), and backfat thickness (0.44 vs 0.30 cm; P = 0.04) were greater after Phase 1. However, carcass lean percentage (58.3 and 57.1%) and the percentage of noncarcass fat (6.39 and 1.07% for Phase 1 and 2, respectively) were similar between phases (P>0.10). In conclusion, change with age of growing crossbred meat goats in levels of carcass and noncarcass fat may be dissimilar, and backfat thickness may not be a reliable indicator of differences among ages in whole body, carcass, or noncarcass fat. Average daily gain and efficiency of feed utilisation were substantially lower when Boer x Alpine wether kids were reared to 50 vs 31 wk of age, which must be compared with magnitudes of change in carcass traits and the importance of such characteristics to product value when determining optimal slaughter age and time.