It was conducted an experiment in the Department of Animal Science at Lavras Federal University in order to verify the influence of different crude protein levels (CP) and digestible lysine (DLys) in the diet on the organs weight, physiologic parameters and utilization of nitrogen in the diet for piglets. It was utilized a total of 83 barrows and females (initial weight = 9.1 kg ± 1.2 kg and final weight = 21.5 ± 4.8 kg), crossbred (Landrace x Large White), weaned at 28 days old, allotted in groups of two in nursery in a randomized block design (RBD) in time, in 2x4 factorial scheme (CP x DLys), with five repetitions, during 35 days. The diets were formulated with two levels of CP (16 and 18%) and four levels of true digestible lysine (0.7; 0.9; 1.1 and 1.3%) with correction of the values for methionine and threonine following the ideal protein concept. At the final of experiment, one animal (experimental unit) of each treatment was slaughtered and the pH of estomacal and cecal contents, weight relative of the liver, pancreas and kidney and height of villous and crypts depth of jejune were taken. In the Experiment II, 32 barrows (initial weight = 25 ± 1.3 kg) proceeding from previous experiment, were allotted individually in metabolism cages (experimental unit) in RBD in time, in 2x4 factorial scheme (CP x LYSD) with four repetitions in order to evaluate the nitrogen intake (NI), absorbed nitrogen (AN), retained nitrogen (RN) and NR/NA relations (%). There were no differences for the slaughtered variables analyzed. In the NR there was linear increasing effect (P<0.01) of the DLys levels in NI and quadratic effect (P<0.01) for RN and RN/AN, that showed increase until 1.05 and 1.06% DLys levels, respectively, independent of the CP levels. There were no differences (P>0.05) for AN for any treatments studied. It was conclude that the DLys and CP levels had any effect on organs weight, physiologic parameters and jejune morphometry, but they improve N Retention up to 25% with 1.05% of DLys in diets with reduced levels of CP.
amino acids; physiology; nutrition; ideal protein
