Níveis de proteína bruta para leitoas dos 30 aos 60 kg mantidas em ambiente de alta temperatura (31oC)

this experiment was conducted to evaluate levels of crude protein (cp) for growing gilts, under high temperature environment. the internal temperature at room was maintained at 30.7 ± 0.61°c, with relative humidity of 66.4 ± 7.7%, and the calculated black globe humidity index (bghi) in period was of 81.1 ± 1.36. forty crossbred gilts, with average initial weight of 29.7 ± 1.60 kg, were allotted to an experimental design of randomized blocks with five treatments (16, 17, 18, 19 and 20% cp), four replicates and two animals per experimental unit. the experimental diets were isoenergetics (3400 kcal of de/kg) and were formulated to meet the animals requirements, except for cp. diet and water were fed ad libitum to animals, until the end of the experimental period, when the gilts reached the average weight of 60.0 ± 1.93 kg. average daily weight gain was not affected by the treatments. however the feed:gain ratio quadraticly improved up to level of 18.26% cp. the protein and lysine intakes increased linearly with dietary cp levels . however the lysine levels of diet did not influence the diet and digestible energy intakes. fat deposition rate (fdr) in carcass quadractly changed and decreased up to 19.48% of cp in diet, while the protein deposition rate (pdr) linearly increased. despite of quadract and linear effects of treatments, respectively, on fdr and pdr, the "linear response plateau" (lrp) model was the one that better fitted to the data and the levels of protein were estimated in 18.38 and 18.12% , the plato point for fdr and pdr. gilts in the growing phase, under heat stress environment, require 18.26% cp in the diet for better performance and carcass composition.