Relação ideal dos aminoácidos essenciais para mantença, crescimento e produção de aves

The traditional dose-response method used to determine the ideal essential amino acid ratio (IAAR) has been considered too costly, especially when breeders are used, because an assay for each essential amino acid (EAA) is necessary. On the other hand, the deletion method has been considered a quick and practical way to determine the IAAR, because only one assay is required. Thus, the aim of this thesis was to determine the optimal ratio of essential amino acids for breeders (broiler breeder hens and roosters) and broilers using the deletion method. The first study aimed to estimate the essential amino acid profile and the ideal ratio for maintenance of poultry by deletion method. A nitrogen (N) balance trial was conducted using 198 adult roosters, housed individually in metabolic cages. The treatments were 33 purified diets being 11 diets with an EAA mixture providing high protein intake of 500 mg N/BWkg per day, 11 diets providing medium protein intake of 250 mg N/BWkg per day (in each diet one EAA tested was reduced 50%) and 11 diets providing low protein intake of 125 mg N/BWkg per day (made by omitting the EAA tested). Each treatment had six replicates. After 48 h of fasting receiving water plus sucrose, the roosters were fed 40 g of the diets by tube once a day for three days. The excreta were collected within 72 h after the first feeding. The diets and excreta were analyzed for nitrogen content. For each EAA studied, a linear regression was fitted by N balance and EAA intake. The maintenance requirements were estimated as the EAA intake to maintain the N balance equal to zero. The daily EAA requirements for maintenance were estimated to be: Lys 11, Met 29, Thr 23, Trp 5, Arg 50, Val 29, His 6, Gly 54, Phe 49, Leu 78 and Ile 21 mg/BWkg per day. Therefore, the EAA ratio for maintenance was concluded to be Lys 100, Met 276, Thr 220, Trp 48, Arg 467, Val 275, His 60, Gly 511, Phe 467, Leu 735 and Ile 198% independent of the scale. The EAA profile and the ideal ratio for maintenance of poultry estimated in this study contribute to improve factorial model for estimating EAA requirements for poultry. In the second study, two approaches using amino acid deletion method, one with comparative slaughter and another with N balance, were used to re-evaluate the actual assumptions of ideal ratios between the EAA: lysine (Lys), methionine+cystine (Met+Cys), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val), isoleucine (Ile), leucine (Leu), phenylalanine+tyrosine (Phe+Tyr), glycine+serine (Gly+Ser), and histidine (His) for growing broilers of Cobb 500 genotype during three periods (I: 6 to 21, II: 22 to 37, and III: 38 to 53 d). Per trial, 120 male chickens were housed in metabolic cages for assessment of individual N-balance and AA efficiency data. An AA balanced diet (BD) was formulated according to recommendations of Brazilian tables (Rostagno et al., 2011) for the ideal protein in growing broilers. The diets with different limiting AAs were created by dilution of BD with corn starch to achieve 0.70 of the AA level in BD and supplemented with crystalline AAs, except the AA under study. The AA diluted diets led to significant impairment of protein utilization and indicated valid limiting position of these AAs. Also, at start and the end of the trial a group of birds with mean body weight of each replicate was killed with no blood loss to determine nitrogen deposition by comparative slaughter technique. The mean value of the optimum ratios