Effects of Fortifying Low Crude Protein Diet with Crystalline Amino Acids on Performance, Blood Ammonia Level, and Excreta Characteristics of Broiler Chicks

Abstract

A study was conducted in a completely randomized design to evaluate the performance, excreta characteristics, and some blood nitrogen metabolite concentrations of 28-d-old male broilers fed 4 experimental diets in which CP was decreased in a stepwise manner from 23 to 17%. The other 4 diets were formulated to have 19 and 17% CP, in which 2 of them contained an additional 10% of particular essential amino acids (EAA) and 2 were supplemented with Gly and Glu. Ileal digestible quantities of all EAA were almost equal in the diets, and total amount of each EAA was maintained at or above NRC requirements. Decreasing dietary CP below 19% depressed performance and appetite and increased fat deposition in the whole body and abdominal cavity significantly. Adding the Gly and Glu mixtures to low-CP diets improved performance and decreased fat deposition. Uric acid, moisture, and acidity of excreta were decreased by reduction of dietary CP; excretory ammonia level was increased in 17% CP diets. Blood ammonia level was increased and plasma uric acid was decreased with reduction of CP to 17%. Supplementing Gly and Glu increased plasma and excretory uric acid level in spite of decreasing blood ammonia concentration. The aminostatic hypothesis cannot explain the sharp reduction in appetite in this experiment, because alteration of dietary CP had no significant influence on most plasma free amino acid levels. Therefore, reduction of CP to 19% not only does not impair performance but also decrease nitrogen, ammonia, and pH of excreta that may improve upon litter and air quality. Adding large amounts of crystalline EAA to diets with low intact CP increased blood and excretory ammonia concentration, which due to its negative effects on tissue metabolism may be the main cause of retarded growth and appetite in decreased CP diets below 19%.

Moisture content in broiler excreta is influenced by excreta nutrient contents1

“…Crude protein was included in the model and an increased nitrogen excretion was related to greater excreta moisture content. This is in line with results reported by Ferguson et al (1998a) and Namroud et al (2008). Elevated dietary protein content (overformulation of diets) or an imbalanced amino acid profile has been identified as a cause of wet litter (Collet, 2006;Namroud et al, 2009).…”

Dietary protein effects on growth performance, carcass traits and expression of selected jejunal peptide and amino acid transporters in broiler chickens

“…The latter effect had been previously observed by other investigators when feeding reduced dietary CP diets to broiler chickens (Lipstein et al, 1975;Moran et al, 1992;Deschepper & DeGroote, 1995;Moran et al, 1996;Bartov & Plavnki, 1998). Furthermore, a previous study associated the increase in abdominal fat percentage with overall fat tissue deposition when feeding a reduced CP diet to broilers (Namroud et al, 2008). However, some of the previously mentioned investigators have disagreed when reporting breast meat yield responses as a consequence of dietary CP reduction.…”

Teores de glicina+ serina total em dietas de baixa proteína bruta para de frangos de corte de 22 a 35 dias de idade

“…Os dados foram submetidos à análise de variância, e os resultados obtidos com as dietas de baixos níveis proteicos com diferentes níveis de glicina+serina foram comparados à dietacontrole pelo teste Dunnett. As análises dos dados foram feitas por meio do programa SAEG (Sistema…, 2007 Vários autores relataram queda no desempenho de frangos de corte na fase de crescimento alimentados com dietas que continham baixos teores de PB (Sabino et al 2004;Rigueira et al, 2006;Namroud et al, 2008). Porém, de acordo com os resultados obtidos e nas condições em que o experimento foi realizado, vê-se que foi possível reduzir o teor de PB das dietas de frangos de corte para 17% na fase de crescimento sem que houvesse prejuízos sobre as variáveis de desempenho.…”