Assessment of Non-Phytate Phosphorus Requirements of Chinese Jing Tint 6 Layer Chicks from Hatch to Day 42.

Simple Summary: The non-phytate phosphorous (NPP) requirements of laying hens vary significantly at different stages of growth and development due to their differing physiological characteristics. Non-linear models and factorial methods are often used to estimate the nutritional requirements of animals at different stages of growth. In this study, the NPP requirement of Chinese Jing Tint 6 layer chicks from hatch to d 42 was evaluated using both a non-linear model and factorial method. The non-linear models were fitted based on the criterion of growth performance, serum biochemical parameters, bone characteristics, and phosphorus utilization. The factorial methods were used to classify the requirements of the layer chicks into growth requirements and maintenance requirements. Based on the current results, it was recommended that dietary 0.367% and 0.439% NPP benefit from the best P utilization of 1–14 and 15–42 d birds, respectively. By predicting the nutritional needs of poultry at different stages as accurately as possible, the model can help formulate more scientific and reasonable feed formulation. We aimed to estimate the non-phytate phosphorus (NPP) requirements of Chinese Jing Tint 6 layer chicks. We randomly allocated 720 birds to five treatments with six cages of 24 birds each, feeding them a corn–soybean diet containing 0.36%, 0.41%, 0.46%, 0.51%, and 0.56% NNP. The results showed that the body weight gain (BWG), tibial length, and apparent total tract digestibility coefficients (ATTDC) of P were affected (p < 0.05) by dietary NPP level. A quadratic broken-line analysis (p < 0.05) of BWG indicated that the optimal NPP for birds aged 1–14 d was 0.411%. Similarly, 0.409% of NPP met tibial growth needs. However, 0.394% of NPP was optimal for P utilization according to the ATTDC criterion. For 15–42 d birds, 0.466% NPP, as estimated by the BWG criterion, was sufficient for optimal growth without decreasing P utilization. Using the factorial method, NPP requirements were calculated as 0.367% and 0.439%, based on the maintenance factors and BWG for 1–14 and 15–42 d birds, respectively, to maintain normal growth. Combining the non-linear model with the factorial method, this study recommends dietary NPP levels of 0.367% and 0.439% for 1–14 and 15–42 d birds, respectively, to optimize P utilization without affecting performance. [ABSTRACT FROM AUTHOR]