Extending the productive laying cycle of aging hens requires maintaining physiological function and egg quality across different stages of production. Molting requires substantial amounts of protein, amino acids, and energy for feather regeneration, which may compete with immune responses for limited nutritional resources. During the late laying phase, increasing egg weight and declining eggshell quality present another challenge. This seminar reviews two studies examining immunological trade-offs during molt and amino acid regulation during late lay. The first study used lipopolysaccharide (LPS) to induce an acute phase response (APR) in molting and non-molting hens. Molting hens showed weaker hepatic interleukin-6 (IL-6) and interleukin-8 (IL-8) responses, while plasma IL-1β and IL-6 did not show marked increases in non-molting hens. Similar responses in normally feathered and Scaleless High hens suggested that the dampened pro-inflammatory response was associated with the broader physiological state of molt rather than feather growth alone. The second study evaluated digestible lysine (dLYS) and the ratio of digestible total sulfur amino acids to dLYS (dTSAA:dLYS) in hens from 62 to 74 weeks of age. Reducing dLYS from 5.9 to 5.5 g/kg controlled the increase in egg weight and decelerated the decline in eggshell breaking strength. However, excessive reductions in dTSAA:dLYS reduced egg weight and daily egg mass, indicating that dTSAA supply must be maintained at a sufficient level to sustain production performance. Together, these studies show that aging hens face different nutritional challenges at different physiological stages. During molting, nutrient allocation may be associated with trade-offs in immune responses, whereas during late lay, amino acid supply must be balanced to maintain egg weight control, eggshell quality, and production performance. Stage-specific nutritional regulation may therefore be important for extending productive laying cycles in aging hens.
- Akbari Moghaddam Kakhki, R., C. Alfonso-Carrillo, and A. I. García-Ruiz. 2023. The impact of digestible lysine and sulfur amino acids on eggshell quality and egg weight control in old ISA brown hens during 62 to 74 wk. Poult. Sci. 102:102860. doi:10.1016/j.psj.2023.102860
- DeRogatis, A. M., R. A. Hernandez, J. C. Suico, and K. C. Klasing. 2025. Molt dampens pro-inflammatory cytokine production during the acute phase response to lipopolysaccharide in the domestic chicken (Gallus domesticus). Dev. Comp. Immunol. 172:105461. doi:10.1016/j.dci.2025.105461
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