Graded Levels of Dietary Valine in Protein‐Restricted Diets: Effects on Reproductive Performance and Tissue Morphology in Laying Japanese Quail
Morteza Pashaei Jalal, Alireza Alizadeh Moghadam Masouleh, Seyed Davood Sharifi, Abouzar NajafiABSTRACT
Background
Valine (Val) is an essential branched‐chain amino acid that plays a critical role in protein synthesis and reproductive function in poultry. However, the optimal dietary Val requirement for laying Japanese quail fed reduced‐protein diets remains insufficiently defined.
Objective
This study evaluated the effects of graded dietary Val levels on reproductive performance, egg quality, hatchability, and hepatic and ovarian histomorphometry in laying Japanese quail under protein‐restricted conditions.
Methods
A total of 375 Japanese quail (300 females and 75 males; 47–98 days of age) were randomly assigned to five dietary treatments containing 0.65%, 0.75%, 0.85%, 0.95%, or 1.05% Val, with five replicates per treatment. Productive performance was recorded weekly, egg quality traits were assessed periodically, and organs weights, ovarian follicular development, and hepatic histomorphology were evaluated at the end of the experiment.
Results
Dietary Val significantly affected egg production, egg mass, and feed conversion ratio ( p < 0.05). Quail fed 0.95% Val achieved the highest egg production and the most efficient feed conversion. Egg physical characteristics, including size and shape indices, were also improved at this supplementation level. Hatchability traits were not significantly influenced by dietary Val, although true hatchability was numerically greatest in the 0.95% Val group. Histological analyses demonstrated enhanced folliculogenesis and reduced hepatocyte and nuclear diameters in birds receiving 0.95% Val, indicating improved ovarian development without evidence of hepatic stress.
Conclusion
Approximately 0.95% dietary Val optimizes reproductive performance, egg quality, and ovarian development in laying Japanese quail fed reduced‐protein diets. Increasing Val beyond this level provides no additional productive advantages and may impose greater hepatic metabolic demand.