The effect of amino acid requirement and low -protein diets on egg production parameters, egg quality and nitrogen excretion in laying hens

Because of the hens inefficiency to digest protein sources (40%), researchers have been investigating the use of low-protein diets to reduce nitrogen excretion. In order to further develop the concept of low-protein feeding, two trials were conducted to evaluate total sulfur amino acids (TSAA) and lysine levels, TSAA/lysine ratios and low-protein diets for laying hens. Current research evaluating lysine and TSAA intakes to maximize performance determined that lysine intakes of 959 and 816 mg/hen/day for 23 to 40 (P1) and 41 to 60 (P2) wks of age, respectively, maximized egg weights, albumen percentage and decreased yolk percent. Egg production and feed consumption for Dekalb Delta hens were not affected by the increased lysine consumption. Hens consuming 811 and 699mg TSAA/hen/day for P1 and P2, respectively, had significantly greater hen weight gains and yolk solids and improved feed efficiency, while reduced specific gravity. During trial two, Hyline W-98 laying hens were fed low-protein diets combined with TSAA/lysine ratios from 20 to 60 weeks of age. Protein intakes of 14.4 and 13.8 g/hen/day (Phase 1 and 2) significantly decreased egg production, feed consumption, hen weight gain, egg weight, albumen parameters, albumen and yolk protein percent and specific gravity, while increasing yolk percent and protein rete. Lowering the protein intake from 18.9 to 16.3 and 16.3 to 14.6 g/day had no effect on the aforementioned parameters. Hens fed diets containing the ratio .82 and .72 (Phase 1 and 2) performed at the highest level compared to higher ratios. Reducing dietary protein affected the protein synthesis machinery (RNA and DNA) by increasing RNA and decreasing protein per gram of tissue. Decreasing protein intake improved protein retention by 9 and 4% during phases I and II, respectively. Combining the reduced dietary protein intake with the improvement in protein retention, there was a 32 and 16% reduction in protein excretion