Possibility of crude protein reduction in laying hen diet: Effect of dietary lysine, methionine + cystine, and threonine concentration

Yazdanpanah, F., Taheri, H.R., Hajilou, M. and Kiani, A. 2023. Possibility of crude protein reduction in laying hen diet: effect of dietary lysine, methionine+cystine, and threonine concentration. Animal Nutrition and Feed Technology, 23: 107–117.

This study was designed to investigate the effect of different concentration of lysine, methionine + cystine, and threonine in low-CP-diets on productive performance and egg quality of laying hen from 40 to 52 weeks of age. A total of 270 laying hens (Hy-line W36) were assigned to five dietary treatments with nine replicate cages per treatment and six hens per cage. Dietary treatment includes a control diet (16.5% CP), and two low-CP-diets: 15.34% CP (supplemented with 100 and 107% of lysine, methionine + cystine, and threonine of the control diet) and 14.19% CP-diet (supplemented with 107 and 114% of lysine, methionine + cystine, and threonine of the control). All low-CP-diets supplemented with lysine, methionine + cystine, and threonine to 100–114% of the control diet (requirement) showed similar egg production, egg weight, total abnormal eggs, mortality, feed intake, feed conversion ratio, yolk color, yolk weight, albumen weight, Haugh unit and the specific gravity of egg compared to that of the control; However, the 15.34% CP-diet plus lysine, methionine + cystine, and threonine to 100% of the control prevented egg mass depression compared to that of the control.