Determination and stage-specific prediction models for standardized ileal amino acid digestibility of corn in peak- and late-laying hens.

Accurate estimation of amino acid (AA) availability is essential for precision poultry nutrition, yet current standards often ignore stage-specific physiological changes in laying hens. This study determined the standardized ileal digestibility (SID) of AA in ten corn samples collected across China to establish stage-specific prediction equations for Lohmann laying hens during peak (40 wk) and late (75 wk) production stages. A total of 792 healthy hens were evaluated in a randomized complete block design (396 hens/stage; 11 treatments/stage; 6 replicates/treatment; 6 hens/replicate). Dietary treatments comprised 10 test diets containing different corn sources as the sole crude protein (CP) source and 1 nitrogen-free diet to estimate basal endogenous AA losses (IAAend). Substantial nutritional variability was observed among corn sources, particularly in acid detergent fiber (ADF, CV = 26.80%), crude fiber (CF, CV = 24.03%), neutral detergent fiber (NDF, CV = 16.08%), and CP (CV = 8.49%). Standardized ileal digestibility coefficients of some AA were significantly higher in peak hens than in late hens (P < 0.05). Specifically, the average SID of Lys declined from 88.67% at peak lay to 75.96% in late hens (P = 0.010), and Met SID decreased from 93.58% to 85.93% (P = 0.016). Multiple linear stepwise regression yielded high-accuracy prediction models (R2 > 0.90) based on corn chemical constituents, such as Met SID at peak lay (R2 = 0.843, P = 0.030) and Lys SID in late hens (R2 = 0.936, P = 0.004). In conclusion, corn AA digestibility is strongly dictated by the physiological laying stage. Integrating these stage-specific prediction equations into commercial feed formulation tools can enhance AA utilization efficiency, reduce nitrogen excretion, and optimize feed costs for commercial egg producers.