Optimal dietary non-phytate phosphorus (NPP) is essential in poultry to maximise productive and reproductive
performance, along with indices of egg and bone quality. This study aimed to establish the NPP
requirements of egg-type duck breeders aged from 54 to 80 weeks on the following traits: egg production,
egg incubation, egg quality, tibial characteristics, reproductive organ, plasma indices, and the
expression of genes related to phosphorus absorption. Longyan duck breeders aged 54 weeks (n = 300)
were randomly allotted to five treatments, each containing six replicates of 10 individually caged birds.
Birds were fed corn-soybean meal-based diets containing 0.18, 0.25, 0.32, 0.38, and 0.45% NPP/kg for
27 weeks. The tested dietary NPP levels did not affect egg production or egg quality indices. The hatchling
weight of ducklings increased (quadratic, P < 0.01) as dietary NPP level increased, and the highest value
occurred with 0.25% NPP. The number of large yellow follicles (LYF), and the relative weights of LYF and
ovary showed linear and quadratic responses to dietary NPP levels; the lowest number and relative
weight of LYF occurred with 0.38% NPP, and the lowest ovarian weight was obtained with 0.25% NPP.
There were no differences in tibial length, breaking strength, and mineral density in response to dietary
NPP levels. In contrast, tibial content of Ca increased (linear, P < 0.01) with dietary NPP levels increasing
from 0.18 to 0.45%, and the tibial content of P increased at 0.32% NPP and the higher dietary NPP levels.
Plasma concentration of P showed a quadratic (P < 0.05) response to the dietary NPP levels, where the
highest value was seen at 0.38% NPP. In conclusion, dietary NPP levels from 0.18 to 0.45% had no effects
on egg production, and egg and tibial quality of duck breeders. The duck breeders fed a diet with 0.25%
NPP showed the highest hatchling weight of their offspring, while those fed 0.38% NPP had the lowest
number and relative weight of LYF. These results indicated that the diet with 0.25% NPP can be used
in egg-type duck breeders to improve the hatchling weight of their offspring, without adverse effects
on their productivity. The regression model indicated that the maximal hatchling weight of ducklings
was obtained from duck breeders fed the diet with 0.30% NPP.