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.

This study aimed to investigate the effects of dietary crude protein (CP) and lysine levels on growth performance, slaughter performance, meat quality, and myofiber characteristics of slow-growing chicken. A 3 × 3 factorial experiment was arranged, and the chickens were fed with 3 levels of dietary CP (16.0%, 17.0%, 18.0%) and 3 levels of dietary lysine (0.69%, 0.84%, 0.99%). A total of 540 8-week-old Beijing-You Chicken (BYC) female growing chickens were randomly allocated to 9 groups, 5 replicates per group, and 12 chickens per replicate. The birds were randomly allocated to one of the 9 experimental diets. Growth performance, slaughter performance, meat quality, and myofiber characteristics were determined at 16 weeks of age. The results showed that dietary CP level and the interaction of dietary CP and lysine levels affected average feed intake (AFI) (p < 0.05). The AFI in the 16.0% CP and 17.0% CP groups was higher than in the 18.0% CP group (p < 0.05). Dietary CP levels significantly affected body weight gain (BWG) (p < 0.05) at 9 to 16 weeks. The 18.0% CP group had the highest BWG (93.99 g). Dietary CP levels affected the percentage of leg muscle yield, and the percentage of leg muscle yield of the 16.0% CP group was significantly lower than that in the other two groups (p < 0.05). Dietary CP and lysine levels alone and their interactions did not affect pH_24h, drip loss, and cooking loss of breast muscle (p > 0.05). The shear force of the 18.0% CP group (29.55 N) was higher than that in the other two groups (p < 0.01). Dietary CP level affected myofiber characteristic (p < 0.01), with the lowest myofiber density (846.35 p·mm⁻²) and the largest myofiber diameter (30.92 μm) at 18.0% CP level. Dietary lysine level affected myofiber diameter, endomysium thickness, perimysium thickness (p < 0.01), with the largest myofiber diameter (29.29 μm) obtained at 0.84% lysine level, the largest endomysium thickness (4.58 μm) at 0.69% lysine level, and the largest perimysium thickness (9.26 μm) at 0.99% lysine level. Myofiber density was negatively correlated with myofiber diameter and endomysium thickness (R = −0.883, R = −0.523, p < 0.01); perimysium thickness had a significant negative correlation with shear force (R = −0.682, p < 0.05). Therefore, reducing dietary CP level and adding appropriate lysine can reduce myofiber diameter and increase perimysium thickness, reducing shear force and improving meat tenderness. A high lysine level (0.99%) in the low-CP (16.0%) diet can improve meat tenderness by regulating the myofiber characteristic without affecting production performance.

This study aimed to investigate the effects of dietary calcium (Ca) and non-phytate phosphorus (NPP) levels alone and in interaction on performance, egg quality, lipid metabolism, antioxidant capacity and follicular development in aged local laying hens. A total of 900 44-week-old Beijing You Chicken (BYC) laying hens with an average body weight of 2.13 ± 0.12 kg were randomly allocated to nine groups (100 hens/group, four replicates of 25 hens). A 3 × 3 factorial design was used with Ca at 3.0%, 3.4%, 3.8% and NPP at 0.31%, 0.36%, 0.41%, respectively. After 1 week of adaptation, the trial lasted from 45 to 58 weeks of age. The results showed that dietary Ca and the NPP level alone did not affect the egg-laying rate of BYCs during 45–58 weeks (p > 0.05), but their interaction affected egg mass (EM, p = 0.049). The group with 3.0% Ca and 0.31% NPP exhibited the highest EM (0.22 kg). At 52 weeks of age, the dietary Ca level affected yolk color (YC): 3.4% Ca and 3.6% Ca increased YC (p < 0.05). Dietary 0.41% NPP decreased YC (p < 0.05). The Ca and NPP interaction affected the albumen height (AH), Haugh unit (HU) and YC (p < 0.05). The group with 3.0% Ca and 0.41% NPP had the highest AH (5.14) and HU (73.46). At 58 weeks of age, 3.4% Ca indicated the lowest YC (p < 0.05). Moreover, 0.36% NPP had the lowest YC and the highest RYW (p < 0.05). Significant Ca × NPP interactions were observed for eggshell thickness (EST), AH, HU, YC, and egg grade (EG) (p < 0.05). The group with 3.0% Ca and 0.41% NPP exhibited the highest AH, HU, YC, and EG. The Ca × NPP interaction affected high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) content (p < 0.05). Dietary 0.41% NPP increased serum malondialdehyde (MDA) content (p = 0.020). The group with 3.0% Ca and 0.41% NPP had the lowest serum LDL-C (p < 0.05). Dietary Ca, the NPP level alone, and their interaction might not affect the number of large yellow follicles and graded follicles at 58 weeks of age (p > 0.05). The 0.36% NPP and 0.41% NPP increased the number of small yellow follicles (p = 0.021). The group with 3.4% Ca and 0.36% NPP had the highest number of small yellow follicles (25.75 ± 4.34, p = 0.033). In summary, the dietary Ca and NPP interaction, rather than Ca or the NPP level alone, contributed to egg mass, egg quality, lipid metabolism and small yellow follicles in the late laying period. An excessive NPP level (0.41%) may not bring additional benefits to the late laying hens’ performance and could lead to increased peroxidation in the aging local laying hens.