Establishing an essential amino acid profile for maintenance in poultry using deletion method

Abstract

This study aimed to estimate the essential amino acid profile and the ideal ratio for the maintenance of poultry by deletion method. A nitrogen balance (NB) trial was conducted using 198 adult roosters, housed individually in metabolic cages. The treatments were 33 purified diets being 11 diets with an amino acid mixture providing high protein intake of 500mg N/BWkg0.75 per day, 11 diets providing medium protein intake of 250mg N/BWkg0.75 per day (in each diet, one amino acid tested was diluted 50%) and 11 diets providing low protein intake of 125mg N/BWkg0.75 per day (made by omitting the amino acid tested). Each treatment had six replicates. After 48h of fasting receiving water plus sucrose, the roosters were fed 40g of the diets by tube once a day for 3days. The excreta were collected within 72h after the first feeding. The diets and excreta were analysed for nitrogen content. For each amino acid studied, a linear regression was fitted by NB and amino acid intake (AAI). The maintenance requirements were estimated as the AAI to maintain the NB equal to zero. The daily amino acid 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 21mg/BWkg0.75 per day. Therefore, the amino acid 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 essential amino acid profile and the ideal ratio for the maintenance of poultry estimated in this study contributed to improve the factorial model for estimating essential amino acid requirements for poultry.