The effects of different levels of diet metabolizable energy on performance, egg traits and blood parameters of aged laying hens

This experiment was conducted to evaluate the effects of different levels of diet metabolizable energy on performance, egg traits and blood parameters of aged laying hens. In this experiment 192 Hy-line (W36) laying hens were used from 65-74 weeks of age in 4 treatments, 4 replicates and 12 hens in each replicate in a completely randomized design. The amounts of ME were 2800, 2900 (control group), 3000 and 3100 kcal/kg in 1-4 experimental groups. The highest egg weight, egg percentage, egg mass, the best feed conversion, the lowest feed cost for production each kilogram of egg, the highest egg color index, albumin and yolk, Haugh unit and egg shell thickness were observed in diet contained 2900 kcal/kg ME. High level of energy in diets, reduce the amount of feed intake and egg production, Haugh unit and shell thickness. In using low ME in diet, as the amount of feed intake without egg production improve increased, the production cost increased, whereas the egg color index, eggshell percentage and Haugh unit reduced. Using different levels of diet metabolizable energy did not have any significant effects on blood biochemical parameters and immune cells of laying hens (P<0.05). The overall results showed that in aged laying hens using diets with 2900 kcal/kg metabolizable energy in comparison with other metabolizable energy levels improve the performance and egg traits.