Digestible lysine requirement for laying hens from 50 to 66 weeks of age

ABSTRACT With the objective of determining the requirement of digestible lysine for brown-egg laying hens in the period from 50 to 66 weeks of age, an experiment was carried out using 150 Shaver Brown laying hens, distributed in a completely randomized design, with five treatments (digestible lysine levels: 0.79, 0.82, 0.85, 0.88 and 0.91%), six replications and five birds per experimental unit. The production of eggs, weight and the egg mass, feed intake and lysine, feed mass and dozen eggs, specific gravity, Haugh unit, yolk and albumen index, percentage of albumen, yolk and bark were analyzed. Feed intake, feed conversion per dozen of eggs s and per egg mass, egg production, egg weight and egg mass were not influenced (P>0.05) by digestible lysine levels. There was a linear increase in lysine intake (P<0.01) with increasing levels of this amino acid in the diets. The albumen, yolk and shell percentages were not influenced (P>0.05) by studied digestible lysine levels. Lysine levels had a quadratic effect (P>0.05) Haugh unit and albumen index being estimated as 0.884 and 0.868% digestible lysine levels, respectively. For yolk index, the association of the quadratic model to Linear Response Plateau (LRP) estimated the level of 0.903% digestible lysine. When the aim is to maximize the internal egg quality, a dietary level of 0.884%, 0.868% and 0.903% digestible lysine for Haugh unit, albumen index and yolk index, respectively is recommended.摘要：本研究旨在明确50至66周龄褐壳蛋鸡的可消化赖氨酸需求量。试验选用150只夏弗农褐壳蛋鸡（Shaver Brown laying hens），采用完全随机试验设计，设置5个处理组（可消化赖氨酸水平分别为0.79%、0.82%、0.85%、0.88%及0.91%），共6个重复，每个试验单元饲养5只蛋鸡。测定指标涵盖产蛋率、蛋重、总蛋重、采食量、赖氨酸摄入量、饲料转化率、每打鸡蛋饲料转化率、蛋比重、哈氏单位（Haugh unit）、蛋黄指数与蛋白指数，以及蛋白、蛋黄及蛋壳的占比。结果表明，可消化赖氨酸水平对采食量、每打鸡蛋饲料转化率、总蛋重饲料转化率、产蛋率、蛋重及总蛋重均无显著影响（P>0.05）。随着饲粮中赖氨酸添加水平的提升，赖氨酸摄入量呈线性升高趋势（P<0.01）。试验设置的可消化赖氨酸水平对蛋白、蛋黄及蛋壳占比均无显著影响（P>0.05）。赖氨酸水平对哈氏单位与蛋白指数具有二次效应，据此估算得到哈氏单位与蛋白指数对应的最佳可消化赖氨酸水平分别为0.884%和0.868%。对于蛋黄指数，采用二次模型与线性响应平台模型（Linear Response Plateau, LRP）联合分析，估算得到最佳可消化赖氨酸水平为0.903%。若以最大化蛋内品质为目标，推荐饲粮可消化赖氨酸水平分别为：哈氏单位对应0.884%、蛋白指数对应0.868%、蛋黄指数对应0.903%。