Frangos de corte fêmeas alimentadas com rações contendo diferentes níveis de proteína bruta suplementadas com aminoácidos sintéticos

Abstract

Three experiments were conducted at the Poultry Module Agricultural Sciences Center of the Federal University of Paraíba - Campus Areia - PB, in order to determine the appropriate level of crude protein in diets for broilers at three housing stages, initial ( 1 to 10 days), growth (11 to 21 days) and final (22 to 42 days). In each experiment were used 720, 648 and 540 female broilers of the "Cobb" bread, according to the animal stage, distributed in a completely randomized design with six treatments and six repetitions with 20, 18 and 15 birds respectively. Treatments consisted in providing diets formulated based on digestible amino acids containing six different dietary protein levels. We evaluated the performance data (weight gain, feed intake and feed conversion) and carcass characteristics (carcass, breast, thighs, the thighs, the back, wings, liver, gizzard, the heart and abdominal fat yields). We also evaluated body composition of these animals. Data were subjected to analysis of variance and regression using the computer program ASSISTAT 7.7. beta (SILVA; Azevedo, 2008) to study the effect of different levels of protein. For the first experiment, the protein level did not affect feed intake. However, it was observed a quadratic effect affecting the weight gain and feed conversion, and estimated levels of crude protein that provided the best results in weight gain and feed conversion: 22.1% and 21.91% respectively. The carcass and cuts yields were not influenced by CP levels, however, the relative weights of the liver and gizzard were higher in birds fed high levels of PB. The body composition variables of the birds showed no significant effect on the parameters of ash and moisture. However, showed significant linear effect in the studied parameters protein and fat, in view of the decrease of muscle ether extract with reduced level of crude protein in the feed. However, birds fed 19% CP were more efficient in protein deposition and thereby, excreted less nitrogen in the environment. In the second experiment, it was observed linear effect of CP levels on weight gain, feed intake and feed conversion of the birds, with the level of 22.8%, 17.8% and 22.8% crude protein respectively. It was not observed effect of treatments on carcass traits and body composition at 21 days. But when it evaluated the efficiency and utilization of crude protein, it was found that the level of 17.8% CP showed better results, but not there among treatments, a significant difference to the deposition of crude protein in the carcass. There was a linear effect on consumption and nitrogen excretion with protein reduction. For the experiment III, was not observed effect of reduced CP levels on performance parameters, carcass yield, however, abdominal fat showed a linear effect when it reduced the dietary crude protein, which presented more with the level of 15.5% CP. Thus, depending on the breeding of birds stage, you can use the concept of ideal protein for improving the performance variables and carcass yield.