The Effect of Dietary Concentrations of Digestible Lysine and Sulphur Amino Acids on The Productive Performance and Egg Quality Traits in Aged Laying Hens.

Abstract

<h4>Background</h4>Most laying hen diets are based on corn-soybean meal, in which methionine and lysine are limiting amino acids.<h4>Objectives</h4>This study aimed to investigate on the effects of digestible lysine (dLys) and total sulphur amino acids (dTSAA) levels in the diet on productive performance of aged laying hens.<h4>Methods</h4>A total of 384 Shaver White laying hens aged 105‒116 weeks were used in a randomized complete block design as a 2×4 factorial, with 8 treatments and 6 replicates of 8 hens each. Main effects included dLys concentrations of 0.75% and 0.80% and dTSAA of 0.70%, 0.73%, 0.76% and 0.79% of diet.<h4>Results</h4>Diet containing 0.80% dLys and 0.73% dTSAA increased egg weight (EW) during 109‒112 week and overall period (p < 0.05). The interaction effects of dLys and dTSAA at the levels of 0.80 dLys along with 0.73% dTSAA resulted in the highest EW at the age of 105‒108 weeks (p < 0.05). Egg mass, egg production, feed intake, feed conversion ratio and egg quality indices including albumen quality, shell thickness, yolk, albumen and shell percentages were not significantly affected by the different levels of dLys and dTSAA in the diet.<h4>Conclusions</h4>Increasing the level of dTSAA in the diet increased EW, but increasing the level of dLys had no significant effect on this index. The highest EW was observed in dLys 0.80% with dTSAA 0.73% and the lowest EW was observed in dLys 0.75% with dTSAA 0.79% during 105-116 weeks of age. The highest egg specific gravity was observed in the dLys level 0.75% with dTSAA 079%.