Modeling of leucine requirement for growth and egg production

Abstract

The objective of this study was determine leucine maintenance requirement (Leu) and to evaluate the responses of broiler chickens and laying hens to the intake of diets with increasing Leu levels. For the maintenance study, two nitrogen balance (N) trials with 36 roosters each will be conducted. Assay 1 will consist of providing a Leu-deficient diet with Leu levels between 0 and 1.741%, while Assay 2 will be a control, to confirm that leucine is the first limiting amino acid in diets, with Leu levels varying between 0 and 2.002%. The balance of N will be calculated as the difference between the consumption of N and the excreted N. The requirement of Leu for laying type poultry will be obtained through a study with 120 laying hens from Lohmann white lineage. There will be 8 treatments randomly distributed, being 7 increasing levels of Leu and one control, with 15 replicates of one bird each. The dilution technique will be used to formulate the diets. The response variables will be: egg production, Feed Intake (FI), egg weight and percent egg yolk and albumen. The Reading model will be adjusted to estimate the optimal Leu intake. The experiment with broilers will be performed in three phases (1 to 14 days, 15 to 28 days and 29 to 42 days of age), using 1280 birds in each phase (640 males and 640 females). The treatments will be randomly distributed in a factorial scheme 7 x 2 + 1 (seven levels of Leu x two sexes + one additional treatment), with four replicates of 20 birds each. The dilution technique will be used to formulate the diets. The variables studied will be: weight gain, FI, feed conversion, protein and fat deposition in the body and feathers and efficiency of utilization of Leu. The Reading model and factorial models will be adjusted to determine the Leu requirement. Data from these studies will be submitted to statistical analysis using SAS 9.3 software. (AU)