In the present study will investigate the effect of duration of hatching period on the quality and performance chicks ahead or not to heat stress. For this, three experiments will be performed. In experiment 1, fertile eggs of broilers (Cobb ®) will be incubated at 37.5 ° C and 60% RH up to 12 days. From the 13th day of incubation to hatching incubators two will be maintained at 37.5 ° C incubator and two have its temperature raised to 39.0 ° C. In the pre-and post-hatching shall be assessed the characteristics of the eggshells, and the hatching of the birds will be assessed the quality of chicks, incubation duration, and characteristics of the blood and lung of chicks. In experiments 2 and 3, the incubation is carried out as in experiment 1. In experiment 2, after hatching, the area is determined thermoneutral poultry according to the incubation temperature (37.5 ° C and 39 ° C), which consists in a preference test temperature and a thermal challenge, which will be held on the 1st, 7th, 14th, 21st, 28th and 35th days of life and in subsequent days, respectively. In experiment 3, soon after hatching, chicks from each treatment incubation (37.5 ° C and 39 º C) will be placed in growth chambers under controlled environment and maintained at three different temperatures thermoneutral recommended for the strain, thermal preference (determined from data from experiment 2) and warm in relation to thermal preference. At 42 days old will analyze the performance characteristics, carcass, blood, meat quality, and hypertrophy and hyperplasia of muscle fibers. The data will be checked as to the presence of outliers, normality of errors (test-Cramer-Von Mises) and homogeneity of variances (Levene test). After verified the compliance with the assumptions of the model, the data will be submitted to analysis of variance, using SAS ® and in case of difference, will apply the test of Tukey (5%) to compare means.
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