Optimizing Productive Performance of Laying Hen and Egg Quality Under Cold Stress: A Dietary Approach With Crude Protein, Methionine and Zinc

Background Cold stress reduces egg production and quality in laying hens by increasing energy demands for thermoregulation, thereby limiting nutrients for reproduction and disrupting ovarian function and calcium metabolism. Objectives This study aimed to evaluate the effects of dietary crude protein (CP), methionine (Met) and zinc (Zn) levels on laying performance and egg quality of hens under cold stress conditions. Methods A total of 432 Lohmann LSL‐Lite hens (65 weeks old) were allocated to 12 dietary treatments in a 3 × 2 × 2 factorial arrangement, with six replicates per group. Treatments included three CP levels (15.80%, 14.30%, 12.80%), two Met levels (0.3%, 0.22%) and two Zn levels (0 and 30 mg/kg). Birds were housed under cold stress conditions (5°C–13°C) for 12 weeks. Results Reducing dietary CP improved egg production, feed conversion ratio, and egg mass ( p < 0.05). Higher Met (0.3%) increased egg weight compared to 0.22% Met ( p < 0.05). Significant interactions between CP and other dietary factors (Met, Zn) affected egg shape index and Haugh unit ( p < 0.05). The lowest CP and Met levels resulted in the poorest egg shape index, while 0.22% Met combined with 14.30% CP yielded the highest Haugh units. Conclusion Lowering CP improved laying performance under cold stress with minimal effects on most egg quality traits; however, interactions between CP and Met influenced egg shape index and albumen quality. The study concluded that optimal results were achieved with diets containing 14.30% CP, 0.30% Met and 30 mg/kg Zn.