Dekalb Delta hens were randomly assigned to one of eight dietary treatment groups. Two intakes of lysine (860 and 959 mg/hen per day) and 4 intakes of TSAA (635, 689, 811, 877 mg/hen per day) were combined in a 2 x 4 factorial treatment arrangement and fed from 20 to 43 wks of age. A phase feeding regimen was implemented at 43 wk with lysine intake lowered to 715 or 816 mg/hen per day and TSAA to 578, 607, 699, or 779 mg/hen per day. Cage was the experimental unit (5 hens/cage), and dietary treatments were replicated 8 times. Egg production (EP) and feed consumption were not affected by dietary treatments. Feed efficiency improved linearly by increasing TSAA intake during phase I only. Hen weight gain was improved (P < or = 0.03) by increased dietary lysine (94.2 vs. 135.2 g weight gain/hen). During phase I, hen weight gain was affected quadratically (P < or = 0.02) by TSAA. Increasing TSAA intake up to 689 mg/hen per day increased hen weight gain, but gain decreased at the highest intake. Egg weights (EW) increased (P < or = 0.02) from 59.02 to 60.21 g with increased lysine intake. Increasing lysine intake increased wet and dry albumen percentage, whereas dry yolk percentage decreased with increasing lysine. Total sulfur amino acid intake affected wet yolk, dry yolk, and solids in a quadratic trend, with hens fed 811 and 699 mg/d producing eggs with the greatest yolk solids. Wet and dry shell percentages were not affected by lysine or TSAA, and specific gravity decreased linearly during phase II and overall, with increased dietary TSAA. In conclusion, the dietary lysine at 959 and 816 mg/hen per day for phases I and II, respectively, optimized EW and feed efficiency. Because EP was not affected by dietary lysine, the dietary level for optimizing EP is closer to 860 and 715 mg/hen per day for phases I and II, respectively. Dietary TSAA level for maximum EP and feed efficiency was near 811 and 699 mg/hen per day but for EW may be closer to 877 and 779 mg/hen per day for phases I and II, respectively.

A 3 x 3 treatment arrangement varying in dietary protein and TSAA:Lys was used to evaluate the effect of low-protein diets fed to Hy-Line W-98 laying hens. Phase I was 20 to 43 wk of age with 18.9, 17.0, and 14.4 g of protein/hen per day and 0.97, 0.85, and 0.82 TSAA:Lys, whereas phase II was 44 to 63 wk of age with 16.3, 14.6, and 13.8 g of protein/hen per day and 0.92, 0.82, and 0.72 TSAA:Lys. Egg production and feed consumption decreased from 83.7 to 82.2% and 98.8 to 95.6 g, respectively. Feed efficiency improved from 1.680 to 1.645 g of feed/g of egg mass with decreasing dietary protein. Body weight gain was similar for hens fed high or medium protein diets. In phase II, hens consuming 13.8 g of protein/day had significantly reduced egg weight compared with hens consuming 14.6 or 16.3 g of protein/day. Wet and dry albumen percentage, albumen solids, and albumen and yolk protein percentages were significantly decreased with feeding low-protein diets. Yolk protein percentage was increased from 14.85 to 15.11% when decreasing the ratio from 0.97 to 0.82. Hens consuming a low-protein diet produced eggs with the lowest specific gravity. An interaction was observed for protein retention during phase I, feeding 14.4 g of protein/day or a ratio of 0.97 improved protein retention by 9 and 16%, respectively. Overall, hens consuming 16.3 or 14.6 g of protein/hen per day performed similar to hens consuming 18.9 and 17.0 g of protein/hen per day during P1 and P2, respectively. Also, hens consuming diets containing 0.97 and 0.92 TSAA:Lys produced eggs with improved shell quality as compared with other ratios during P1 and P2, respectively.

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