This study evaluated the performance, carcass yield and quality, and physiological stress indicators of broilers of three genetic strains reared at three housing densities for 29 days. A total of 828 day-old male chicks, with average initial weight of 40.0± 2.0g were used. Three genetic strains (Cobb 500, Ross 808, and Ross 508, with 276 birds each) and three housing densities (17, 19, and 21 broilers/m²) were tested. A completely randomized experimental design in a 3 x 3 factorial arrangement, with four replicates of 23 birds each, was applied. The following responses were evaluated: performance parameters (average weekly body weight, average daily gain, feed intake, feed conversion ratio), physiological stress indicators (blood glucose levels, blood cell counts), and carcass yield and quality (dermatosis, bruising, dermatitis, and femoral degeneration scores). Average weekly body weight (BW) and daily weight gain (DWG) were not influenced by rearing density (p≥0.05), but Cobb 500 broilers were the heaviest during the analyzed period. In the second week, Ross 508 birds showed better feed conversion ratio (FCR) when housed at the density of 17 broilers/m² (p≤0.001), whereas the best FCR of Ross 808 and Cobb 500 broilers was obtained at 21 broilers/m² (p≤0.001). Carcass yield was not influenced by the treatments (p≥0.05). Physiological stress indicators were not affected by the treatments, and remained within normal ranges (p≥0.05). Dermatosis scores (scratches) increased (p≤0.05) when housing density increased from 17 to 19 broilers /m².

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About 33.3% of chicken life is conditioned by the result of embryonic development. Therefore, understanding and improving the early phase of the broiler's life is critical to guarantee their well-being. Thus, the objective of this research was to evaluate the relationship between the breeder's age, breed and the incubator types on quality and animal welfare in the hatchery. The experimental design was completely randomized in a 2 x 2 x 3 factorial arrangement (incubator, breed and age), with 12 treatments and 6 replicates each. The eggs derived of Cobb 500 and Ross's breeders at the beginning of the laying period, middle age and at the end of the laying period. It is concluded that the size of the eggs is related to the breeder's age and breed, which influences directly the number of bled eggs. In addition, well-being in the hatchery can be affected by decreased hatching and contamination that is higher in older breeders. Cobb eggs also need more attention because they are larger, therefore, they have a higher risk of breakage and they are more sensitive to the low concentration of CO 2 at the hatcher.

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