ArticleJournal of animal physiology and animal nutrition2026
Dietary L-Tyrosine Sustains Egg Production and Quality by Modulating Promoter CpG Methylation, Gene Expression, and Hormone Profiles in Reproductive Signalling Pathways of Aged Laying Hens.
Article in Journal of animal physiology and animal nutrition, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
Managing prolactin (PRL)-mediated reproductive suppression is critical for maintaining egg production in commercial laying hens. L-tyrosine (TYR), a precursor of dopamine (DA), may counteract age-related reproductive decline by suppressing PRL, thereby sustaining productivity and egg quality in late-phase laying hens. The present study evaluated the effects of dietary L-tyrosine supplementation on laying performance, egg quality, reproductive hormone profiles, gene expression, and promoter CpG methylation in aged laying hens. A total of 180 Atak-S laying hens (71 weeks old) were randomly assigned to three dietary treatments, each with six replicates of 10 hens, and were fed a basal diet without L-tyrosine (control) or the basal diet supplemented with 0.5 g/kg (TYR0.5) or 1 g/kg (TYR1) L-tyrosine for 12 weeks. Hens in the TYR1 group exhibited higher hen-day egg production, improved feed conversion ratio, and significantly greater eggshell weight, shell thickness, Haugh unit, yolk index, and albumen index than the control group (p < 0.05). Dietary L-tyrosine increased plasma DA and serum estradiol while reducing serum PRL (p < 0.05). L-tyrosine also upregulated the expression of key dopaminergic and reproductive signalling genes, with corresponding promoter hypomethylation (p < 0.05), whereas PRL mRNA expression tended to decrease with concurrent promoter hypermethylation. A significant negative correlation was observed between target gene expression and promoter CpG methylation levels (p < 0.05). These findings indicate that dietary L-tyrosine modulates reproductive hormone profiles and molecular responses within reproductive signalling pathways, resulting in improved laying performance and egg quality. Therefore, L-tyrosine may represent a promising nutritional intervention to sustain reproductive function and productivity in late-phase laying hens.
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