Abstract
Background:
The demand for sustainable, natural feed additives in the poultry industry is gradually increasing to make production more efficient and increase the quality of the products, especially in spent laying hens.

Aim:
This study examined the benefits of dietary dried lemon citrus peel (DLCP) supplementation on egg performance and egg quality in aged laying hens at the end of their production life.

Methods:
Eighty Lohmann hens at 64 weeks postmolt age and 2700 ± 75 g average body weight were randomly divided into four dietary treatment groups: basal diet (control, T1), basal diet + 10 g/kg DLCP (T2), basal diet + 15 g/kg DLCP (T3), and basal diet + 20 g/kg DLCP (T4). The experiment lasted for 4 weeks with four replicates of five hens for each treatment. The productivity performance and internal and external egg quality traits were evaluated.

Results:
The egg production rates were significantly higher (p < 0.05) in T3 and T4 than in T1 and T2 (mean egg obtained = 27.75 and 26.75 eggs, respectively). In all tested groups, feed intake increased step by step throughout the weeks, whereas the maximum feed intake (112.60 g) was noted in T4. T3 showed only a marginal difference after T4 but had a similar trend. Feed conversion ratios were also improved in the T3 (2.59) and T4 (2.60) groups compared with the control group (3.30), whereas egg mass values were increased in the T3 (47.10 g) and T4 (49.90 g) groups. In T4, external egg quality traits: egg weight (69.05 g), shell thickness (3.00 mm), and shell weight (9.00 g) were maximized.

Conclusion:
Similarly, T4 showed better results for the internal quality attributes such as yolk height, width, and weight. The T4 group showed a higher egg production of about 15% than the control group, indicating a clear improvement in laying performance. Based on this finding, a diet containing 20 g/kg DLCP will enhance production and egg quality and can sustainably facilitate the use of agricultural residues for layer feeding.

Key words: Dried lemon citrus peel; Egg production; Egg quality; Feed additive; Spent hens.