The present study aimed to determine the influence of low crude protein diet (LCP, 13%) enriched with methionine (Met) and lysine (Lys) and different zinc levels with or without vitamin D3 on the productive and reproductive performance of Gimmizah chickens during the late laying period. A total number of 320 Gimmizah chickens (280 hens + 40 cocks) aged 52-week were individually weighed and randomly divided into eight treatment groups with five replicates per each during the experimental period (52 - 64 weeks of age). Birds of the first group were fed the basal diet and served as control. Second one was fed LCP, 13% without any supplementation. Whereas, the third group fed LCP diet enriched with Met (0.6 g/kg diet) and Lys (1.4 g/kg diet), to equalize their corresponding levels of the basal diet. The fourth and fifth groups were fed LCP diet enriched with Met and Lys supplied with zinc (Zn, 50 and 100 mg/kg diet, respectively). The sixth group was fed LCP diet enriched with Met and Lys supplied with vitamin D3 (Vit D3, 2000 IU/kg diet). While, the seventh and eighth groups were fed LCP diet enriched with Met and Lys supplemented with Zn (50 mg/kg diet) plus Vit D3 (2000 IU/kg diet), and Zn (100 mg/kg diet) plus Vit D3 (2000 IU/kg diet), respectively. The chickens fed LCP diet represented the worst significant records of egg production, egg weight, egg mass and fed conversion ratio compared with control. While, groups fed LCP diet enriched with Met and Lys alone or supplemented with studied agents similarly restored the previous parameters to control level. Egg shell weight, shell thickness, SWUSA, hatched chick weight and hatchability percentages for aged chickens fed LCP diet enriched with Met and Lys alone or supplemented with both Zn levels were significantly improved compared with control. Birds fed LCP diet enriched with Met and Lys supplemented with Zn levels plus Vit D3 significantly improved Hgb, PCV, WBCs, lymphocyte, phagocytic activity, HDL, LDL, TAC, SOD, MDA and Ca compared with control and LCP diet groups. Total protein, albumin, globulin, total lipids and triglycerides for birds fed LCP diet enriched with Met and Lys alone or supplied with Zn levels with or without Vit D3 did not represent any significant differences compared with control.
In conclusion, feeding Gimmizah chickens LCP (13%) diet enriched with Met and Lys alone is adequate for achieving the optimal productive and reproductive performance besides best record of net returns during the late laying period.