An experiment was performed to evaluate the effect of the incubation system ― multiple-stage (MS) and single-stage (SS) ― on the characteristics at hatching, intestinal morphology, metabolism, and performance of Cobb-500 chickens from 1 to 40 d of age. A total of 1,968 fertile eggs were incubated in two setters under commercial conditions. Birds hatched in SS were longer than those hatched in MS, and the females had higher relative intestinal weight compared with males. However, at hatching, there were no differences in BW and yolk-free body mass from incubation system or sex. In the period from 1-40 d, the birds hatched in SS were heavier, had higher weight gain and better adjusted feed conversion, without differences in feed intake and feed conversion. This result is due mainly to MS females, which always, although in some periods only numerically, exhibited worse responses than the other treatment, lowering the average MS bird performance. Sex influenced the duodenal villi height in chickens at 0 d; females showed larger villi than males. Moreover, the birds hatched in SS had deeper crypts than those hatched in MS. At 7 d, because males had higher feed intake, the differences in duodenal villi height found at hatching disappeared, leaving only a gender effect on jejunum crypt depth: females showed deeper crypts. As regards the metabolism coefficients of nutrients from 5 to 7 d, females were more efficient in metabolizing energy and showed higher apparent metabolizable energy corrected for nitrogen values than males, with no differences caused by the incubation system. The best incubation conditions are obtained with the single-stage system, based on the improved broiler performance (2.98%), especially in the females (5.04%).
hatching; intestinal morphology; multi-stage; single-stage