Exigência de treonina digestível para codornas japonesas

Abstract

This work had as objective to estimate the nutritional requirement of digestible threonine (ThrD) for Japanese quails in in three stages of growth (1 to 7, 8 to 14 and 15 to 42 days of age), and early production. Besides evaluating the nitrogen balance (NB) and metabolizable coefficient (MC) as a function of increasing ThrD levels, the effects of the levels provided in the rearing, in the laying, and to verify the effects of increasing levels of ThrD on organ weight (liver, heart, intestine and oviduct), morphometry and intestinal length, oviduct length, body chemical composition, rate of protein and fat deposition and retained energy in the carcass and egg quality. In the growth phases, the design was completely randomized, with five levels of ThrD (0,58; 0,70; 0,82; 0,94 and 1,06%), five replicates and 30 quails per experimental unit (UE), totaling 2250 birds. For the evaluation of NB and MC was used the same diets and design, however in digestibility cages with five birds per UE, totalizing 125 birds from 28 to 35 days of age. To determine the effects that the levels provided in the rearing (15 to 42 days of age) were in the laying phase, twelve birds from each UE from rearing phase were transferred to cages at 42 days of age, where they received a basal diet and the productive performance and eggs quality were evaluated in three productive cycles of 21 days each. The experimental design in the production phase was completely randomized, containing five levels of ThrD (0,52; 0,60; 0,68; 0,72 and 0,84%), with five replicates and 12 quails per experimental unit, totaling 300 birds, with initial average weight of 149.78 ± 4.33g from 58 to 120 days old. For the levels provided in the growth phases there was no significant effect on the performance, body chemical composition and relative weight organs in the three phases. The jejunum morphometry of the indicated an increasing linear behavior of the villus: crypt relationship at 7 and 14 days of age and a linear decreasing of the crypt depth at 14 days of age. The NB and MC did not present significant effects. The ThrD levels fed during the rearing phase linearly increased the initial and final body weight of the birds in the laying phase. For the levels provided at the production stage the body weight, laying rate, feed conversion per kg of eggs, feed conversion per dozen eggs and mass of eggs showed a quadratic effect on ThrD levels, and the consumption of threonine increased linearly with increasing levels. Among egg quality variables, only the egg weight presented statistical difference, being influenced in a quadratic way by ThrD levels. The relative weights of the organs were not significant, but the intestine length, villus height and villus: crypt ratio presented quadratic effect. It is concluded that the ThrD level of 0.58% in the growth diet provides adequate growth and satisfactory performance of Japanese laying quails. And the level of 0.70% of ThrD was estimated as a recommendation for diets formulation of Japanese quails in the laying initial phase