This study testified the hypothesis that L threonine (Thr) and canthaxanthin (Cx) alone or in combination   in absence or present of anhydrous sodium sulphate (SS), can improve the performance of local laying hens in their second laying cycle   (100- 112 weeks). One hundred and ninety two aged Golden Montazah layer hens that reached 100 weeks of age were chosen and distributed randomly into 8^th experimental groups. Each group contained 24 hens divided into 3 replicates of 8 hens each. The 1^st group fed control diet, the groups from the 2^nd to 8^th fed control diet supplemented with Thr, Cx, Cx+Thr, SS, SS+Thr, SS+Cx,  or SS+Thr+Cx respectively. Egg production performance, egg quality, plasma protein respiration rate and body temperature were estimated.

The results indicated that Thr supplementation improved significantly egg production percent, egg mass and increased significantly feed intake. Feed conversion ratio improved during the first month by supplemented control diet with Thr, and Cx. Moreover plasma globulins and heat tolerance during summer season improved by Thr supplementation. Combination of Thr and Cx supplementation led to attain more improvement in egg production performance. Compared to the control diet, combination of Thr and Cx supplementation increased egg mass per hen by 25.18 %. However, no improvement was detected in egg production performance of aged Golden Montazah during summer season due to SS supplementation the control diet.
The results proved the hypothesis that egg production performance of aged Golden Montazah hens improved by threonine and/or canthaxanthin supplementation.