RESUMO
Three experiments were conducted, from January until September 2001, to estimate the optimized age to apply feed restriction to control mortality from ascites, with no negative effects on production and carcass characteristics of broilers. For each experiment, 1,200 1-d-old mixed Ross x Peterson chicks were reared in floor pens (50 chicks in each) and fed commercial feed. Feed restriction was applied for 8 h/d for 14 d at 21 or 28 d of age in experiment 1, 14 or 21 d in experiment 2, and 7 or 14 d in experiment 3. In experiments 2 and 3, a microelement supplement (without or with) was tested; the control groups received feed ad libitum and no supplement. Body weight gain, feed conversion, total mortality, and mortality from ascites, leg problems, and carcass characteristics were considered at the end of each experiment. The data were analyzed as a completely randomized design, or as a 2 x 2 factorial to estimate main and interaction effects (experiments 2 and 3). Additional analyses, including the control, were done; means comparisons were by orthogonal contrasts. The production and carcass characteristics of the restricted groups were lower than the control but were not statistically different in experiments 2 and 3, although the optimized age for feed restriction was at 7 d. Total mortality and mortality from ascites decreased by restriction, but leg problems increased without supplement. The results indicated that quantitative feed restriction and microelement supplementation at 7 d of age reduced mortality from ascites and leg problems and permitted compensatory growth sufficient to equal the production characteristics of the control group at 49 d of age. However, it is necessary to determine the specific microelements to be supplemented and to estimate the effects of season and genetic line.
