Abstract
This study investigated the effects of dietary methionine (Met) levels on the bone quality of broilers challenged with coccidia. A total of 600 fourteen-day-old male Cobb500 broilers were gavaged with mixed Eimeria spp. and randomly allocated into 10 treatment groups by a 2 × 5 factorial arrangement. Birds received normal protein diets (NCP) or reduced-protein diets (LCP), containing 2.8, 4.4, 6.0, 7.6, and 9.2 g/kg of Met. Data were analyzed via two-way ANOVA and orthogonal polynomial contrast. At 9 days post-inoculation (DPI), whole body bone mineral density (BMD) and bone mineral content (BMC) linearly decreased as Met levels increased (p < 0.05). For the femoral metaphysis bone quality at 9 DPI, BMD linearly decreased, and porosity linearly increased as Met levels increased (p < 0.05) in the cortical bone. The increased Met levels linearly improved trabecular bone quality in LCP groups (p < 0.05) while not in NCP groups. For the femoral diaphysis cortical bone at 6 DPI, LCP groups had higher BMD and BMC than NCP groups (p < 0.05). Bone volume linearly increased as Met levels increased in LCP groups (p < 0.05) while not in NCP groups. In summary, the results suggested that increased Met levels decreased the cortical bone quality. However, in the context of reduced-protein diets, the increased Met levels improved trabecular bone quality.