Lysine and zinc chelate in diets for brown laying hens: effects on egg production and composition

It was evaluated the effects of levels of digestible lysine and chelate zinc combined in the diet for laying on the egg quality. It was used 720 birds, from 48 to 60 weeks of age, distributed in a completely randomized design in a 3 × 5 factorial scheme with three levels of zinc and five levels of lysine, applied into six replicates in the experimental units of eight birds per plot. The levels were: 137, 309 and 655 ppm zinc and 0.482, 0.527, 0.582, 0.644 and 0.732% digestible lysine. It was not observed any interaction among digestible lysine and zinc for the primary variables of fractions and egg composition. Levels of zinc reduced egg weight, suggesting the lowest efficiency in nutrient intake. At the highest dietary concentration of zinc, the addition of digestible lysine coincided with a linear increase in shell weight. However, zinc addition, regardless of lysine level in the diet, resulted in the reduction of egg weight and of the percentage of mineral matter in the yolk, limiting the efficiency of mineral deposition in this fraction of the egg. Concentration of zinc that produced the best results was 137 ppm inasmuch as higher quantities limit the use of digestible lysine, with effects harming composition and egg quality. The study indicates the following requirement for digestible lysine: 0.639% from the 48th to the 52nd week, 0.679% from the 52nd to 56th week, and 0.635% from the 56th to the 60th week. Considering the total period from 48th to the 60th week, the level 0.638% of lysine or the daily intake of 707 mg of the amino acid met the requirement for egg quality of semi-heavy layers used in this study. Avaliaram-se os efeitos dos níveis lisina digestível e zinco quelato combinados na dieta de galinhas poedeiras sobre a qualidade do ovo. Foram usadas 720 aves de 48 a 60 semanas de idade, distribuídas em delineamento inteiramente casualizado em arranjo fatorial 3 × 5 com três níveis de zinco e cinco níveis de lisina aplicados a seis repetições em unidades experimentais de oito aves por parcela. Os níveis foram: 137, 309 e 655 ppm de zinco e 0,482; 0,527; 0,582; 0,644; 0,732% de lisina digestível. Não se constatou interação de lisina digestível e zinco para as principais variáveis das frações e composição do ovo. O nível de zinco reduziu o peso do ovo e isso sugere menor eficiência na absorção de nutrientes. Na maior concentração dietética de zinco, o acréscimo de lisina digestível coincidiu com aumento linear no peso da casca. Por outro lado,