Nutritional requirement of digestible threonine for brown-egg laying hens from 50 to 66 weeks of age

The dietary requirement of threonine was determined for brown laying hens in the period 50-66 weeks of age, based on performance parameters and quality of eggs. For this we used 150 laying Shaver Brown hens distributed in a completely randomized design with five treatments (0.460; 0.490; 0.520; 0.550 and 0.580%) of digestible threonine, six replications and five birds each. The digestible threonine levels did not affect (p>0.05) feed intake, egg production, egg weight, egg mass or feed conversion kg kg(-1), but presented a quadratic effect (p<0.05) on feed conversion dozen kg-1, where the lower conversion was obtained with a supply of 0.521% threonine in the diet. There was no effect of dietary digestible threonine levels (p>0.05) on the yolk and albumen index, specific gravity, yolk percentage, thickness or shell weight per surface area, since the variable Haugh unit displayed linear behavior (p<0.05) and increased with increasing levels of dietary threonine. The percentage of albumen and shell presented a quadratic effect (p<0.05) according to the dietary levels of threonine, and the best levels of these variables were obtained with a supply of 0.520% and 0.521% digestible threonine in the diet. The dietary requirement of threonine for laying hens, aged between 50 and 66 weeks, based on converting food kg kg(-1), percentage of albumen and shell is 0.521%