Abstract: [Objective] This experiment was conducted to investigate the effects of dietary calcium (Ca) and non-phytate phosphorus (NPP) levels on growth performance and tibia traits of fast growth Yellow-feathered broilers. [Method] A total of 4 050 one-day-old male broilers were randomly divided into 9 groups with 6 replicates per group and 75 broilers per replicate. A 3 (Ca level)×3 (NPP level) two-factor design was used. The experiment lasted for 63 days. The Ca levels were 1.00%, 0.90% and 0.85%, and the NPP levels were 0.46%, 0.38% and 0.30% from 1 to 21 days. The Ca levels were 0.90%, 0.75% and 0.65%, and the NPP levels were 0.42%, 0.35% and 0.28% from 22 to 42 days. The Ca levels were 0.80%, 0.70% and 0.60%, and the NPP levels were 0.39%, 0.31% and 0.23% from 43 to 63 days. Feed and gain ratio (F/G) was calculated for 0~21, 22~42, 43~63 and 0~63 d days by using feed intake and body weight gain. At the end of the feeding experiment, 2 chicks were selected from each replication of each treatment group and slaughtered for chemical analysis of chick tibia and serum level of Ca and P. [Result] The decrease of Ca level had no effect on the growth performance of broilers (P>0.05). The decrease of NPP level had no effect on the growth performance of broilers (P>0.05), but in the starter phase that low NPP level had a higher F/G (P<0.05). Ca level had no effect on tibia traits, the levels of Ca and P in serum of broiler (P>0.05). The contents of Ash and P in tibia, and the level of P in serum of broilers at 63 days of age were all significantly decreased (P<0.05) with the decrease of NPP level. There was no significant interaction between dietary Ca and NPP levels on growth performance and tibia traits of broilers (P>0.05). [Conclusion] Ca requirements of Yellow-feathered broilers seemed to be lower than the nutritional standards of Yellow-feathered broilers recommendations, and it could be reduced by 20%-30%, were 0.85%, 0.65% and 0.60% in the small, medium and large chicken stage, respectively. The decrease of NPP level affects growth performance of chicks and reduces the deposition of calcium and phosphorus in the tibia of broilers. NPP should be maintained at the current level, were 0.46%, 0.42% and 0.39%, respectively.

Key words: Yellow-feathered broilers; calcium level; non-phytate phosphorus level