Nível de proteína bruta e balanço de aminoácidos essenciais da ração pré-inicial (1 a 7 dias) de pintos de corte

Abstract

Two experiments were carried out in order to evaluate performance, nitrogen and dry matter balances and biometrical measures of broiler chicks fed different levels of crude protein (20.0; 21.4; 23.1; and 25.1%), and essential amino acids Lys and Met+Cys (100:76; 100:69, 100:63, and 100:58) on pre-starter phase (1-7d). In each experiment, 200 one-day-old broiler chicks were allotted in a completely randomized design with five treatment groups and four replicates of 10 birds each one. No significant differences were observed for weight, weight gain, feed consumption and feed conversion at 7, 14 and 21 experimental days when the treatments were protein levels. The chicks fed 100 Lys:76 Met+Cys ration showed higher weight, weight gain and feed conversion than those fed 100:69, 100:63 and 100:58 amino acid balance, but not at 14 and 21 d. The best digestibility of dry matter and nitrogen were achieved when the ration contained the lower level of protein (20%) and the higher balance of amino acids (100:76). The relative weight of the liver was higher at´7d with the use of 20 and 21.4% crude protein and 100:76 amino acids in the pre-starter ration. The pancreas relative weight was higher for 7-d-old birds fed 20% crude protein. The results are indicative that increasing proteins levels of pre-starter ration are not a good alternative to improve broiler chick performance, but the formulation could be balanced on the requirements and ideal relationship among essential amino acids, manly Met, Cys and Lys.