Dietary calcium and non-phytate phosphorus levels affect the performance, serum biochemical indices, and lipid metabolism in growing pullets

This experiment aimed to study the effects of dietary calcium (Ca) and non-phytate phosphorus (NPP) levels on performance, serum biochemical indices, and lipid metabolism in Beijing You Chicken (BYC), a local chicken. A 3 × 3 factorial design was adopted, dietary Ca levels were 0.66, 0.71, and 0.76%, NPP levels were 0.25, 0.30, and 0.35%. A total of 648 ten-wk-old BYC growing pullets were randomly divided into 9 groups with 6 replicates per group, and 12 birds per replicate. Growth performance, serum biochemical indices, and lipid metabolism indicators from 10 to 16 wk were measured. The results showed as follows: 1) Dietary Ca and NPP alone did not affect growth performance, but the interaction of dietary Ca and NPP affected average feed intake (AFI) of growing pullets (P < 0.05). The AFI was the lowest for the group with 0.71% Ca and 0.25% NPP (3,550.0 g, P = 0.036). 2) Dietary Ca level significantly affected serum P content (P < 0.05); dietary NPP had an influence trend on serum Ca content (P= 0.054). Dietary NPP levels and the interaction of Ca and NPP significantly affected alkaline phosphatase (AKP) activity. 3) Dietary Ca levels significantly affected TC content and HDL-C content (P < 0.05). Dietary NPP level significantly affected TG content (P < 0.05), the TG content in 0.25% and 0.30% NPP groups was significantly lower than that in 0.35% NPP group (P < 0.05). The interaction of dietary Ca and NPP significantly affected TG, TC and HDL-C contents (P < 0.05). TG, TC, and LDL-C levels were lower and HDL-C levels were the highest in the group with 0.66% Ca and 0.25% NPP. In summary, appropriate dietary Ca level can regulate serum TG, TC, and HDL-C content. Dietary Ca and NPP levels can be adjusted in pullet phase to avoid excessive obesity during the egg-laying period. This study recommended that dietary 0.66% Ca and 0.25% NPP benefit for the lipid metabolism of BYC growing pullets without affecting the performance.