Effect of different levels of autolyzed yeast on performance and egg quality traits in laying hens reared under high stocking density

High stocking density is known as a source of chronic stress, which has an adverse effect on the performance of laying hens. So, the aim of this study was to investigate the effect of different levels of autolyzed yeast on performance and egg quality traits of laying hens reared under high stocking density. This experiment was done using 2 levels of density (2 and 4 birds per cage with dimensions of 38×38 cm) and 4 levels of autolyzed yeast (0, 0.2, 0.4 and 0.6 percentage) with 192 laying hens Hy-line W-80 (35 weeks old) in a completely randomized design with factorial arrangement of 4×2 with 8 replicates. The results of the experiment showed that high stock density decreased the viability and reduced the feather score of birds, but autolyzed yeast increased the viability of birds in high stock density (P≤0.05). Dietary supplementation of autolyzed yeast was not affected feed intake (P≥0.05), but increased egg production and decreased feed conversion ratio (P≤0.05). The increase in egg weight showed a tendency to be significant (P=0.07). Dietary supplementation of autolyzed yeast decreased pH of excreta in laying hens (P≤0.05). Also, autolyzed yeast increased the primary and secondary antibody titer against sheep red blood cell at the 43 and 44 weeks old (P≤0.05). The results of this experiment showed that the supplementation of autolyzed yeast to the diet improved performance and the humoral immune system of laying hens reared at high stock density.